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• 4111. [Article] Understanding the impact of climate change on snowpack extent and measurement in the Columbia River Basin and nested sub basins

  Shifting climate patterns in the Columbia River basin are affecting snow pack, and, as a result, stream flow throughout the region. In the Oregon Cascades, ever growing populations, and their associated ...

  Citation × Citation Citation Abstract Copy Title: Understanding the impact of climate change on snowpack extent and measurement in the Columbia River Basin and nested sub basins Author: Brown, Aimee Lyn Shifting climate patterns in the Columbia River basin are affecting snow pack, and, as a result, stream flow throughout the region. In the Oregon Cascades, ever growing populations, and their associated activities, place increasing stress on an already over allocated hydrologic system. Political pressures, including the possibility of renegotiation or termination of the Columbia River Treaty between the United States and Canada; societal pressures, including a desire for ecosystem services and fish habitat; and economic pressures, including a need for adequate streamflow for hydropower generation and irrigation, all necessitate a better understanding of current and future snow pack. This work focuses on analyzing the ability of the current snowpack measurement system to represent and capture snowpack in the Columbia River basin and its sub basins under both today’s climate and future climates. In addition, this work develops a more comprehensive knowledge of the impact climate warming will have on snow-covered areas across the region. To determine the efficacy of current snow water equivalence (SWE) measurement sites, the locations and characteristics of sites in the McKenzie River Basin, a sub basin of the Columbia River basin, were considered. SWE was distributed through the basin using the physically based model, SnowModel. SWE values at the four SNOTEL sites in the basin ranged from 0.18-0.37 m at peak SWE. Three of the sites had SWE values greater than 180% of average SWE of the snow covered area. Using elevation, aspect and slope, a 16-node binary regression tree explained controlling variables on SWE at the basin scale. As expected, elevation is the primary determinant in SWE distribution, however, the influence of different parameters shifted throughout the accumulation and ablation seasons. Updated high resolution PRISM precipitation and temperature data are used to map areas within the Columbia River basin and two nested sub basins that are at risk of turning from winter snow dominated precipitation regimes to winter rain dominated under warming scenarios ranging from 1-3°C. Within the Columbia River basin, the Oregon Cascades exhibit the greatest degree of sensitivity to changes in precipitation. Under a 2°C warming scenario, an increase that the International Panel on Climate Change finds highly likely to occur within the next 30 years, 30% of current-day snow covered area in Oregon’s Willamette River Basin will be at risk of turning from snow to rain. The water storage that will be lost if such a change does occur (0.73 km3) is equivalent to more than 8 months worth of water at the current rate of water use in the basin. Data from nine regional stations in the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) Cooperative Observer Program were used to validate placement of snow by the model. The conclusions of this work suggest that the placement of snow measurement sites requires refinement and improvement if the measurements are to accurately represent basin wide snowpack today and in the future. Water and natural resource managers will find the results presented here useful for siting future measurement locations that capture and represent SWE during times of interest. While political, societal and economic pressures will only increase, these findings provide early steps for the creation of a more robust system that has the potential to help stakeholders make informed decisions about their water resources, their communities and their needs. Title: Understanding the impact of climate change on snowpack extent and measurement in the Columbia River Basin and nested sub basins Author: Brown, Aimee Lyn Shifting climate patterns in the Columbia River basin are affecting snow pack, and, as a result, stream flow throughout the region. In the Oregon Cascades, ever growing populations, and their associated activities, place increasing stress on an already over allocated hydrologic system. Political pressures, including the possibility of renegotiation or termination of the Columbia River Treaty between the United States and Canada; societal pressures, including a desire for ecosystem services and fish habitat; and economic pressures, including a need for adequate streamflow for hydropower generation and irrigation, all necessitate a better understanding of current and future snow pack. This work focuses on analyzing the ability of the current snowpack measurement system to represent and capture snowpack in the Columbia River basin and its sub basins under both today’s climate and future climates. In addition, this work develops a more comprehensive knowledge of the impact climate warming will have on snow-covered areas across the region. To determine the efficacy of current snow water equivalence (SWE) measurement sites, the locations and characteristics of sites in the McKenzie River Basin, a sub basin of the Columbia River basin, were considered. SWE was distributed through the basin using the physically based model, SnowModel. SWE values at the four SNOTEL sites in the basin ranged from 0.18-0.37 m at peak SWE. Three of the sites had SWE values greater than 180% of average SWE of the snow covered area. Using elevation, aspect and slope, a 16-node binary regression tree explained controlling variables on SWE at the basin scale. As expected, elevation is the primary determinant in SWE distribution, however, the influence of different parameters shifted throughout the accumulation and ablation seasons. Updated high resolution PRISM precipitation and temperature data are used to map areas within the Columbia River basin and two nested sub basins that are at risk of turning from winter snow dominated precipitation regimes to winter rain dominated under warming scenarios ranging from 1-3°C. Within the Columbia River basin, the Oregon Cascades exhibit the greatest degree of sensitivity to changes in precipitation. Under a 2°C warming scenario, an increase that the International Panel on Climate Change finds highly likely to occur within the next 30 years, 30% of current-day snow covered area in Oregon’s Willamette River Basin will be at risk of turning from snow to rain. The water storage that will be lost if such a change does occur (0.73 km3) is equivalent to more than 8 months worth of water at the current rate of water use in the basin. Data from nine regional stations in the National Oceanic and Atmospheric Administration (NOAA) National Weather Service (NWS) Cooperative Observer Program were used to validate placement of snow by the model. The conclusions of this work suggest that the placement of snow measurement sites requires refinement and improvement if the measurements are to accurately represent basin wide snowpack today and in the future. Water and natural resource managers will find the results presented here useful for siting future measurement locations that capture and represent SWE during times of interest. While political, societal and economic pressures will only increase, these findings provide early steps for the creation of a more robust system that has the potential to help stakeholders make informed decisions about their water resources, their communities and their needs. Close

• 4112. [Article] The origin of mid-ocean ridge basalts : insights from trace element contents in anorthite, anorthite-hosted melt inclusions, and ocean core complexes

  The primary goal of this study is to access the processes that alter primary melts after segregation from a mantle source and ultimately form petrologic Layers 2 and 3 of the Ocean Crust. Mineral, melt ...

  Citation × Citation Citation Abstract Copy Title: The origin of mid-ocean ridge basalts : insights from trace element contents in anorthite, anorthite-hosted melt inclusions, and ocean core complexes Author: Weinsteiger, Allison Beth The primary goal of this study is to access the processes that alter primary melts after segregation from a mantle source and ultimately form petrologic Layers 2 and 3 of the Ocean Crust. Mineral, melt inclusion, and whole rock chemical compositions are utilized to further the understanding of 1) the behavior of trace element partitioning between high anorthite plagioclase and basalt melt, 2) the nature of the record preserved by melt inclusions in anorthitic plagioclase in MORB, 3) the variability of melt compositions generated at slow spreading ridges, and 4) the composition of melt and crystals present in an axial magma chamber extrapolated from plagioclase-ultraphyric basalts. The major and trace element compositions of melt inclusions hosted in high anorthite feldspar from Gorda Ridge and Southeast Indian Ridge are used to evaluate the degree to which melt inclusions represent original melts trapped at the time of crystallization versus melts that have been affected by entrapment processes or modified by post-entrapment processes. Melt inclusions that are 'real' melts will display trace element partitioning relationships with the adjacent mineral host that fit known models. Melt inclusions that have been modified by inclusion-specific processes, will not conform to known partitioning models. Using anorthitic plagioclase from pillow basalts dredged from the Gorda Ridge and the Southeast Indian Ridge, our results indicate that there is no apparent correlation between the calculated mineral-inclusion partition coefficients and the size or composition of the melt inclusion. The data is generally consistent with experimentally determined partition coefficients for high anorthite feldspar. However, some samples contain trace element patterns that are consistent with some degree of diffusive re-equilibrium of compatible elements, i.e., Sr, Eu, and Ba. Therefore, although plagioclase-hosted melt inclusions are broadly representative of the magmas from which with anorthite phenocrysts formed, these melts do not represent the unmodified array of primary mantle melts, and are produced by a complex set of processes. The variability of magmas produced at a slow-spreading plate boundary is evaluated using mineral analyses, combined with whole rock compositions of gabbroic and basaltic lithologies and is conducted within a spatial context. Samples are drill cores halves obtained during IODP Legs 304/5 from Sites 1309, 1310, and 1311 that are located on Atlantis Massif, at 30°N on the Mid-Atlantic Ridge. Gabbroic samples span the full range of compositions collected from ocean ridges: primitive troctolites through evolved leuco- and oxide- gabbros and whole rock Mg #s (molar Mg/Mg+Fe²⁺) range from 36 to 89 while basalts span a more limited range (50-67). Gabbroic major and trace element compositions are consistently modeled as representing nearly-pure crystal residuum. Trace elements contents of gabbroic clinopyroxenes are generally in equilibrium with basalt samples, although they span a larger range of equilibrium concentrations than the very narrow range exhibited by the basalts. These findings suggest that gabbros are very pure cumulates and that basaltic melt can be efficiently separated from the residual crystals. Plagioclase ultra-phyric basalts from Southwest Indian Ridge contain greater than 20% plagioclase phenocrysts. Plagioclase An content is generally higher than (molar Ca/[Ca+Na+K] ranges from An94 to An84) the calculated equilibrium composition for respective host melts. Additionally, crystals within a single sample exhibit a variety of zoning patterns, morphologies, and textures. Crystal size distributions of 3 samples are linear and suggest that phenocrysts within a single sample grew in a similar thermal environment. Similar CSD slopes are obtained from each sample indicative of a fairly continuous thermal environment along ridge axis. We make an argument that the best fitting model for the petrogenesis of plagioclase ultra-phyric basalts invokes a magma chamber where convection physically separates low density plagioclase phenocrysts and gradients in intrinsic variables (temperature, pressure, and composition) produce the suite of textures and zoning exhibited by individual crystals within a sample. The bimodal trace element composition of crystals from one sample indicates that melts can exist in chemical isolation until just prior to eruption. Title: The origin of mid-ocean ridge basalts : insights from trace element contents in anorthite, anorthite-hosted melt inclusions, and ocean core complexes Author: Weinsteiger, Allison Beth The primary goal of this study is to access the processes that alter primary melts after segregation from a mantle source and ultimately form petrologic Layers 2 and 3 of the Ocean Crust. Mineral, melt inclusion, and whole rock chemical compositions are utilized to further the understanding of 1) the behavior of trace element partitioning between high anorthite plagioclase and basalt melt, 2) the nature of the record preserved by melt inclusions in anorthitic plagioclase in MORB, 3) the variability of melt compositions generated at slow spreading ridges, and 4) the composition of melt and crystals present in an axial magma chamber extrapolated from plagioclase-ultraphyric basalts. The major and trace element compositions of melt inclusions hosted in high anorthite feldspar from Gorda Ridge and Southeast Indian Ridge are used to evaluate the degree to which melt inclusions represent original melts trapped at the time of crystallization versus melts that have been affected by entrapment processes or modified by post-entrapment processes. Melt inclusions that are 'real' melts will display trace element partitioning relationships with the adjacent mineral host that fit known models. Melt inclusions that have been modified by inclusion-specific processes, will not conform to known partitioning models. Using anorthitic plagioclase from pillow basalts dredged from the Gorda Ridge and the Southeast Indian Ridge, our results indicate that there is no apparent correlation between the calculated mineral-inclusion partition coefficients and the size or composition of the melt inclusion. The data is generally consistent with experimentally determined partition coefficients for high anorthite feldspar. However, some samples contain trace element patterns that are consistent with some degree of diffusive re-equilibrium of compatible elements, i.e., Sr, Eu, and Ba. Therefore, although plagioclase-hosted melt inclusions are broadly representative of the magmas from which with anorthite phenocrysts formed, these melts do not represent the unmodified array of primary mantle melts, and are produced by a complex set of processes. The variability of magmas produced at a slow-spreading plate boundary is evaluated using mineral analyses, combined with whole rock compositions of gabbroic and basaltic lithologies and is conducted within a spatial context. Samples are drill cores halves obtained during IODP Legs 304/5 from Sites 1309, 1310, and 1311 that are located on Atlantis Massif, at 30°N on the Mid-Atlantic Ridge. Gabbroic samples span the full range of compositions collected from ocean ridges: primitive troctolites through evolved leuco- and oxide- gabbros and whole rock Mg #s (molar Mg/Mg+Fe²⁺) range from 36 to 89 while basalts span a more limited range (50-67). Gabbroic major and trace element compositions are consistently modeled as representing nearly-pure crystal residuum. Trace elements contents of gabbroic clinopyroxenes are generally in equilibrium with basalt samples, although they span a larger range of equilibrium concentrations than the very narrow range exhibited by the basalts. These findings suggest that gabbros are very pure cumulates and that basaltic melt can be efficiently separated from the residual crystals. Plagioclase ultra-phyric basalts from Southwest Indian Ridge contain greater than 20% plagioclase phenocrysts. Plagioclase An content is generally higher than (molar Ca/[Ca+Na+K] ranges from An94 to An84) the calculated equilibrium composition for respective host melts. Additionally, crystals within a single sample exhibit a variety of zoning patterns, morphologies, and textures. Crystal size distributions of 3 samples are linear and suggest that phenocrysts within a single sample grew in a similar thermal environment. Similar CSD slopes are obtained from each sample indicative of a fairly continuous thermal environment along ridge axis. We make an argument that the best fitting model for the petrogenesis of plagioclase ultra-phyric basalts invokes a magma chamber where convection physically separates low density plagioclase phenocrysts and gradients in intrinsic variables (temperature, pressure, and composition) produce the suite of textures and zoning exhibited by individual crystals within a sample. The bimodal trace element composition of crystals from one sample indicates that melts can exist in chemical isolation until just prior to eruption. Close

• 4113. [Article] Selenium metabolism in the chick and effects of Vitamin E and selenium on heat stress

  An in vitro study was conducted to investigate the metabolism and distribution of Se⁷⁵-selenite and Se⁷⁵-selenomethionine (SEM) in chick blood. Se⁷⁵-selenite is taken up by RBC (13% within 20 minutes) ...

  Citation × Citation Citation Abstract Copy Title: Selenium metabolism in the chick and effects of Vitamin E and selenium on heat stress Author: Alayan, Mohammad Atta An in vitro study was conducted to investigate the metabolism and distribution of Se⁷⁵-selenite and Se⁷⁵-selenomethionine (SEM) in chick blood. Se⁷⁵-selenite is taken up by RBC (13% within 20 minutes) and expelled into the plasma to become bound to proteins. In contrast, Se⁷⁵-SEM showed a more gradual and continuous buildup in RBC with time, according to a hyperbolic type function. Chromatography of RBC lysates on Sephadex G200 established that Se⁷⁵ from selenite is more specifically incorporated into GSH-Px (MW 150,000), whereas Se⁷⁵ from SEM is mostly incorporated into Hb (MW 66,000). The elution pattern of plasma Se⁷⁵-selenoproteins from Se⁷⁵-selenite or Se⁷⁵-SEM on Sephadex G200 showed that radioactivity is associated with two peaks corresponding to MW >440,000 and 89,000. Binding of Se⁷⁵, from selenite or SEM, to plasma proteins was dependent on the presence of RBC. Addition of GSH and GSSG reductase to plasma gave the same effects as RBC on binding of Se⁷⁵ from selenite, but not from SEM, to plasma proteins. To study the nature of this bond, the resistance of plasma protein bound Se⁷⁵ (from selenite or SEM) to extraction by TCA or exhaustive dialysis was studied and indicated that the element was tightly bound to plasma proteins. Treatment with β-mercaptoethanol followed by TCA, however, caused release of most of the Se⁷⁵ plasma selenoproteins (from both Se sources), suggesting that Se⁷⁵ is present in proteins as a selenotrisulfide bond (Pr-S-Se⁷⁵-S-Pr). This was confirmed by chromatography of the released radioactivity on an amino acid analyzer. Based on these results, an in vitro model of selenium metabolism in chick blood is postulated. After chicks were intubated with Se⁷⁵-selenite or Se⁷⁵-selenomethionine (SEM), the distribution and metabolism of radioactivity, as judged by incorporation into cytosolic proteins of various tissues, were studied. Gel filtration studies indicated that Se⁷⁵ from selenite is more specifically incorporated into erythrocyte GSH-Px (MW 150,000) than Se⁷⁵-SEM. It was observed that chick hemoglobin (Hb, MW 66,000) bound Se⁷⁵ from both sources, and possessed peroxidase activity. A mechanism was postulated to explain Hb peroxidase activity. Results of chromatographing plasma on Sephadex G200 indicated that proteins corresponding to MW of 338,000 are the major carriers of Se⁷⁵ from selenite or SEM 6 hours after dosing, however proteins possessing a MW of 89,000 are the important Se⁷⁵ carriers 96 hours after intubation. Compared to tissues, the liver and kidney contained the highest concentrations of Se⁷⁵. Gel filtration chromatography of tissue cytosols on Sephadex G200 indicated that the majority (34-80%) of Se⁷⁵, from selenite or SEM, is associated with the enzyme GSH-Px 24 hours after dosing. Pancreatic cytosol of chicks dosed with Se⁷⁵-SEM had the majority of radioactivity associated with a peak corresponding to MW 44,500. Evidence for non-glutathione peroxidase selenoproteins were detected in various tissues. These included high molecular weight (>440,000) selenoproteins in cytosols of all tissues examined except in bone marrow, a peak (MW 44,500) specific to selenite but not SEM in liver cytosols, a low molecular weight (MW 25,100) protein in kidney and spleen cytosols from both Se⁷⁵ treatments, and two distinct testicular selenoproteins (MW 35,000 and 263,000) from both Se⁷⁵ treatments. A hypothetical pathway for the incorporation of Se⁷⁵ into selenocysteine-containing proteins (i.e., GSH-Px) is presented to account for these observations. During a study on the effects of high levels of Se and/or Vitamin E on performance under heat stress, a significant depression in gain and feed consumption was found, regardless of treatment. However, feed efficiency significantly improved in heat stressed chicks fed diets high in selenium and Vitamin E when compared to feed efficiency in animals on other dietary regimes. Significantly lower hematocrit levels were found in heat stressed chicks, as compared to control chicks, which were raised under conventional conditions. Se levels in chick blood, liver, kidney, and pancreas, and plasma Vitamin E levels were directly related to dietary Se or Vitamin E content. Dietary Vitamin E supplementation counteracted the effect of heat stress in depressing blood selenium levels, however, the opposite trend was observed in the other organs studied. The pancreas in heat stressed chicks was larger than chicks raised at conventional temperatures. Title: Selenium metabolism in the chick and effects of Vitamin E and selenium on heat stress Author: Alayan, Mohammad Atta An in vitro study was conducted to investigate the metabolism and distribution of Se⁷⁵-selenite and Se⁷⁵-selenomethionine (SEM) in chick blood. Se⁷⁵-selenite is taken up by RBC (13% within 20 minutes) and expelled into the plasma to become bound to proteins. In contrast, Se⁷⁵-SEM showed a more gradual and continuous buildup in RBC with time, according to a hyperbolic type function. Chromatography of RBC lysates on Sephadex G200 established that Se⁷⁵ from selenite is more specifically incorporated into GSH-Px (MW 150,000), whereas Se⁷⁵ from SEM is mostly incorporated into Hb (MW 66,000). The elution pattern of plasma Se⁷⁵-selenoproteins from Se⁷⁵-selenite or Se⁷⁵-SEM on Sephadex G200 showed that radioactivity is associated with two peaks corresponding to MW >440,000 and 89,000. Binding of Se⁷⁵, from selenite or SEM, to plasma proteins was dependent on the presence of RBC. Addition of GSH and GSSG reductase to plasma gave the same effects as RBC on binding of Se⁷⁵ from selenite, but not from SEM, to plasma proteins. To study the nature of this bond, the resistance of plasma protein bound Se⁷⁵ (from selenite or SEM) to extraction by TCA or exhaustive dialysis was studied and indicated that the element was tightly bound to plasma proteins. Treatment with β-mercaptoethanol followed by TCA, however, caused release of most of the Se⁷⁵ plasma selenoproteins (from both Se sources), suggesting that Se⁷⁵ is present in proteins as a selenotrisulfide bond (Pr-S-Se⁷⁵-S-Pr). This was confirmed by chromatography of the released radioactivity on an amino acid analyzer. Based on these results, an in vitro model of selenium metabolism in chick blood is postulated. After chicks were intubated with Se⁷⁵-selenite or Se⁷⁵-selenomethionine (SEM), the distribution and metabolism of radioactivity, as judged by incorporation into cytosolic proteins of various tissues, were studied. Gel filtration studies indicated that Se⁷⁵ from selenite is more specifically incorporated into erythrocyte GSH-Px (MW 150,000) than Se⁷⁵-SEM. It was observed that chick hemoglobin (Hb, MW 66,000) bound Se⁷⁵ from both sources, and possessed peroxidase activity. A mechanism was postulated to explain Hb peroxidase activity. Results of chromatographing plasma on Sephadex G200 indicated that proteins corresponding to MW of 338,000 are the major carriers of Se⁷⁵ from selenite or SEM 6 hours after dosing, however proteins possessing a MW of 89,000 are the important Se⁷⁵ carriers 96 hours after intubation. Compared to tissues, the liver and kidney contained the highest concentrations of Se⁷⁵. Gel filtration chromatography of tissue cytosols on Sephadex G200 indicated that the majority (34-80%) of Se⁷⁵, from selenite or SEM, is associated with the enzyme GSH-Px 24 hours after dosing. Pancreatic cytosol of chicks dosed with Se⁷⁵-SEM had the majority of radioactivity associated with a peak corresponding to MW 44,500. Evidence for non-glutathione peroxidase selenoproteins were detected in various tissues. These included high molecular weight (>440,000) selenoproteins in cytosols of all tissues examined except in bone marrow, a peak (MW 44,500) specific to selenite but not SEM in liver cytosols, a low molecular weight (MW 25,100) protein in kidney and spleen cytosols from both Se⁷⁵ treatments, and two distinct testicular selenoproteins (MW 35,000 and 263,000) from both Se⁷⁵ treatments. A hypothetical pathway for the incorporation of Se⁷⁵ into selenocysteine-containing proteins (i.e., GSH-Px) is presented to account for these observations. During a study on the effects of high levels of Se and/or Vitamin E on performance under heat stress, a significant depression in gain and feed consumption was found, regardless of treatment. However, feed efficiency significantly improved in heat stressed chicks fed diets high in selenium and Vitamin E when compared to feed efficiency in animals on other dietary regimes. Significantly lower hematocrit levels were found in heat stressed chicks, as compared to control chicks, which were raised under conventional conditions. Se levels in chick blood, liver, kidney, and pancreas, and plasma Vitamin E levels were directly related to dietary Se or Vitamin E content. Dietary Vitamin E supplementation counteracted the effect of heat stress in depressing blood selenium levels, however, the opposite trend was observed in the other organs studied. The pancreas in heat stressed chicks was larger than chicks raised at conventional temperatures. Close

• 4114. [Article] The effects of red alder leaf fall on the water color and other water quality characteristics of a small watershed in northwest Oregon

  This study was initiated to make some preliminary evaluations of the effects of red alder (Alnus rubra, Bong.) leaf fall on stream water quality, particularly water color. Laboratory tests were also conducted to ...

  Citation × Citation Citation Abstract Copy Title: The effects of red alder leaf fall on the water color and other water quality characteristics of a small watershed in northwest Oregon Author: Taylor, Robert Lynn This study was initiated to make some preliminary evaluations of the effects of red alder (Alnus rubra, Bong.) leaf fall on stream water quality, particularly water color. Laboratory tests were also conducted to better understand the effects of leaf loading, duration of leaf leaching, and type of leaching on changes in water quality. The study focused on the Seaside Municipal Watershed, which is typical of many municipal systems in the Oregon Coast Range. In these systems, streamside alder stands are common and water treatment is limited to chlorination. The potential for coloration of stream water by alder leaves is present but in the fall of 1981 there was no chronic (more than one or two days) low flow water color problem observed at the Seaside diversion in the South Fork of the Necanicum River. The color observed during the lowest flows, which occurred almost through September, averaged 20 platinum-cobalt units of true color. While this is slightly higher than the 5-15 units measured during the winter months and slightly higher than the maximum standard of 15 units set by the USPH for domestic supplies, it is a very faint tint and probably would not cause many complaints by domestic users. Field results showed that the water color can become elevated for short periods at the diversion. There were two occasions when the color was above 20 units (30 units on October 6 and 25 units on November 11). Elevated water color was also observed in a tap water sample from the city's water works building on October 27 (45 units). Each of these color, increases occurred during the beginning of a storm and there was a subsequent drop in color after the storms. This increase in color during storms is probably due to the flushing of storage sites containing dissolved organic material by rising flows. The other water quality characteristics measured (dissolved oxygen, conductivity, pH, nitrate-nitrogen and temperature) showed evidence of. some relationships with leaf fall, but there were no signs of water quality impairment at the city diversion during the autumn of 1981. Laboratory leachings in filtered stream water showed that for a given mass of leaves leached in still water, there is a fairly constant release of color (2 units/hr) for leaching periods between 2 hours and 4 weeks. Running water was more efficient than still water in leaching colored material. There also appears to be a limit to the amount of material that can be removed from a given leaf mass in the first 48 hours of leaching. In still water a linear increase in color occurred with increases in mass loading, and weight loss (as a percentage of original dry weight) was constant. Laboratory tests also showed that ultra violet absorbance may provide a reasonable estimate of dissolved organic carbon concentrations in systems dominated by red alder input. This, however, has yet to be verified with field samples. In a small stream with lower flows than the South Fork of the Necanicum River bounded by an alder stand, color could possibly be a chronic problem during autumn low flows. The South Fork generally appears to have too large a flow for this to normally occur. However, a hypothetical calculation of maximum coloration, under conditions of very low flow and peak leaf fall, resulted in a water color of approximately 110 units in this stream. Short-term increases in color at the beginning of the first few storms would be expected to be more common, in a stream of this size, if there is time for organic matter accumulation in storage sites between storms. Such increases in true color would likely be accompanied by increases in apparent color due to sediment, which may even supercede the coloration due the dissolved or colloidal organic material. Title: The effects of red alder leaf fall on the water color and other water quality characteristics of a small watershed in northwest Oregon Author: Taylor, Robert Lynn This study was initiated to make some preliminary evaluations of the effects of red alder (Alnus rubra, Bong.) leaf fall on stream water quality, particularly water color. Laboratory tests were also conducted to better understand the effects of leaf loading, duration of leaf leaching, and type of leaching on changes in water quality. The study focused on the Seaside Municipal Watershed, which is typical of many municipal systems in the Oregon Coast Range. In these systems, streamside alder stands are common and water treatment is limited to chlorination. The potential for coloration of stream water by alder leaves is present but in the fall of 1981 there was no chronic (more than one or two days) low flow water color problem observed at the Seaside diversion in the South Fork of the Necanicum River. The color observed during the lowest flows, which occurred almost through September, averaged 20 platinum-cobalt units of true color. While this is slightly higher than the 5-15 units measured during the winter months and slightly higher than the maximum standard of 15 units set by the USPH for domestic supplies, it is a very faint tint and probably would not cause many complaints by domestic users. Field results showed that the water color can become elevated for short periods at the diversion. There were two occasions when the color was above 20 units (30 units on October 6 and 25 units on November 11). Elevated water color was also observed in a tap water sample from the city's water works building on October 27 (45 units). Each of these color, increases occurred during the beginning of a storm and there was a subsequent drop in color after the storms. This increase in color during storms is probably due to the flushing of storage sites containing dissolved organic material by rising flows. The other water quality characteristics measured (dissolved oxygen, conductivity, pH, nitrate-nitrogen and temperature) showed evidence of. some relationships with leaf fall, but there were no signs of water quality impairment at the city diversion during the autumn of 1981. Laboratory leachings in filtered stream water showed that for a given mass of leaves leached in still water, there is a fairly constant release of color (2 units/hr) for leaching periods between 2 hours and 4 weeks. Running water was more efficient than still water in leaching colored material. There also appears to be a limit to the amount of material that can be removed from a given leaf mass in the first 48 hours of leaching. In still water a linear increase in color occurred with increases in mass loading, and weight loss (as a percentage of original dry weight) was constant. Laboratory tests also showed that ultra violet absorbance may provide a reasonable estimate of dissolved organic carbon concentrations in systems dominated by red alder input. This, however, has yet to be verified with field samples. In a small stream with lower flows than the South Fork of the Necanicum River bounded by an alder stand, color could possibly be a chronic problem during autumn low flows. The South Fork generally appears to have too large a flow for this to normally occur. However, a hypothetical calculation of maximum coloration, under conditions of very low flow and peak leaf fall, resulted in a water color of approximately 110 units in this stream. Short-term increases in color at the beginning of the first few storms would be expected to be more common, in a stream of this size, if there is time for organic matter accumulation in storage sites between storms. Such increases in true color would likely be accompanied by increases in apparent color due to sediment, which may even supercede the coloration due the dissolved or colloidal organic material. Close

• 4115. [Article] Ecological study of aquatic myxobacteria in a woodland stream

  Most studies of bacteria in water have concerned public health; little attention has been given to organisms which are indigenous to the aquatic environment. Myxobacteria are known to occur in soil, in ...

  Citation × Citation Citation Abstract Copy Title: Ecological study of aquatic myxobacteria in a woodland stream Author: Carlson, René Virginia Most studies of bacteria in water have concerned public health; little attention has been given to organisms which are indigenous to the aquatic environment. Myxobacteria are known to occur in soil, in the marine environment, and several have been studied in relation to diseases of salmonid fishes. However, little information is available regarding the role of myxobacteria in the freshwater environment. The major purpose of this research was to obtain data on the occurrence, distribution, and activities of aquatic myxobacteria in a woodland stream. As a preliminary step for studying the ecology of myxobacteria in the freshwater stream, a culture medium and procedure were developed to provide a means for isolation and enumeration of these organisms. Enumeration of myxobacteria was based on the morphology of the colonies growing on the dilute nutrient medium, cytophaga peptonized milk agar (CPM). The low nutrient concentration of this medium favored spreading of the myxobacterial colony and the production of rhizoid edge patterns which are typical of myxobacteria and distinguishable from eubacterial colonies. The enumeration method was used to obtain data on the occurrence and distribution of myxobacteria as compared to the total bacteria population in Berry Creek. Results of the ecological study conducted over a two and a half year period indicate that myxobacteria are present in this aquatic environment all during the year with highest levels obtained in the fall (October and November) and lowest levels during the summer (July and August). Seasonal variations also occurred in the types of myxobacteria comprising the population of the stream. It is interesting to note that peaks in the myxobacterial and the total bacterial populations occurred in advance of the peak in flow rate. Water temperature and flow rate did not seem to influence the population levels as might be expected if the myxobacteria were transient members of the microbial flora. Additional surveys have shown that the myxobacteria are widespread in fresh water; they have been found in abundance in bottom sediments and surface films as well as in the flowing waters. Myxobacteria also appear to be well adapted to the aquatic environment. It was shown that they are able to utilize the dilute nutrients present in water for their growth. In an attempt to determine the possible role myxobacteria play in the aquatic environment, the predominant myxobacterial types were isolated and studied morphologically and biochemically. All the organisms studied corresponded to the classical definition of myxobacterial cells: gram negative, slender, weakly refractile rodshaped bacteria which exhibit gliding motility. Colony morphology of these myxobacteria plated on CPM has been studied in detail and found to be a constant characteristic of the particular type of myxobacteria isolate. Photographs of several of the predominant forms present in the stream samples illustrate the distinguishable morphology of the myxobacterial colonies. Six morphological groups have been arbitrarily designated on the basis of colony morphology; these morphological groups also show similarities in their biochemical capabilities. Biochemical studies on the myxobacterial isolates indicated that most of the strains were able to utilize simple carbohydrates. All of the isolates were capable of degrading various macromolecules, such as chitin, starch, aesculin, caesin, gelatin, and carboxy methyl cellulose. One of the isolates obtained was strictly proteolytic. The ability to hydrolyze macromolecules appears to be characteristic of aquatic isolates as well as of other myxobacteria. One myxobacterium isolated was believed to be intimately associated with the sheathed bacterium, Sphaerotilus natans. The latter organism was abundant in the sucrose and urea enriched section of Berry Creek. This myxobacterium could not utilize sucrose or urea and occurred only in the enriched section of the stream when Sphaerotilus was present. The fish pathogen, Chondrococcus columnaris was also isolated from Berry Creek water. This myxobacterium can be distinguished from the other aquatic myxobacteria on the basis of its unique colony morphology. This strain of C. columnaris proved to be one of the common serological types found in the Pacific Northwest. Based on the results obtained thus far, it is possible to speculate on the role of myxobacteria in the freshwater environment. All of the myxobacteria isolated in this study are capable of decomposing complex materials, it seems likely therefore, that these organisms may be active in the decomposition of such complex organic compounds, including the remains of other bacterial cells, which are present in the aquatic habitat. Since the isolates studied are also able to utilize the nutrients present at low levels in the stream water, these myxobacteria are not dependent on macromolecular substrates. Myxobacteria with these abilities are apparently well adapted to the aquatic environment. Title: Ecological study of aquatic myxobacteria in a woodland stream Author: Carlson, René Virginia Most studies of bacteria in water have concerned public health; little attention has been given to organisms which are indigenous to the aquatic environment. Myxobacteria are known to occur in soil, in the marine environment, and several have been studied in relation to diseases of salmonid fishes. However, little information is available regarding the role of myxobacteria in the freshwater environment. The major purpose of this research was to obtain data on the occurrence, distribution, and activities of aquatic myxobacteria in a woodland stream. As a preliminary step for studying the ecology of myxobacteria in the freshwater stream, a culture medium and procedure were developed to provide a means for isolation and enumeration of these organisms. Enumeration of myxobacteria was based on the morphology of the colonies growing on the dilute nutrient medium, cytophaga peptonized milk agar (CPM). The low nutrient concentration of this medium favored spreading of the myxobacterial colony and the production of rhizoid edge patterns which are typical of myxobacteria and distinguishable from eubacterial colonies. The enumeration method was used to obtain data on the occurrence and distribution of myxobacteria as compared to the total bacteria population in Berry Creek. Results of the ecological study conducted over a two and a half year period indicate that myxobacteria are present in this aquatic environment all during the year with highest levels obtained in the fall (October and November) and lowest levels during the summer (July and August). Seasonal variations also occurred in the types of myxobacteria comprising the population of the stream. It is interesting to note that peaks in the myxobacterial and the total bacterial populations occurred in advance of the peak in flow rate. Water temperature and flow rate did not seem to influence the population levels as might be expected if the myxobacteria were transient members of the microbial flora. Additional surveys have shown that the myxobacteria are widespread in fresh water; they have been found in abundance in bottom sediments and surface films as well as in the flowing waters. Myxobacteria also appear to be well adapted to the aquatic environment. It was shown that they are able to utilize the dilute nutrients present in water for their growth. In an attempt to determine the possible role myxobacteria play in the aquatic environment, the predominant myxobacterial types were isolated and studied morphologically and biochemically. All the organisms studied corresponded to the classical definition of myxobacterial cells: gram negative, slender, weakly refractile rodshaped bacteria which exhibit gliding motility. Colony morphology of these myxobacteria plated on CPM has been studied in detail and found to be a constant characteristic of the particular type of myxobacteria isolate. Photographs of several of the predominant forms present in the stream samples illustrate the distinguishable morphology of the myxobacterial colonies. Six morphological groups have been arbitrarily designated on the basis of colony morphology; these morphological groups also show similarities in their biochemical capabilities. Biochemical studies on the myxobacterial isolates indicated that most of the strains were able to utilize simple carbohydrates. All of the isolates were capable of degrading various macromolecules, such as chitin, starch, aesculin, caesin, gelatin, and carboxy methyl cellulose. One of the isolates obtained was strictly proteolytic. The ability to hydrolyze macromolecules appears to be characteristic of aquatic isolates as well as of other myxobacteria. One myxobacterium isolated was believed to be intimately associated with the sheathed bacterium, Sphaerotilus natans. The latter organism was abundant in the sucrose and urea enriched section of Berry Creek. This myxobacterium could not utilize sucrose or urea and occurred only in the enriched section of the stream when Sphaerotilus was present. The fish pathogen, Chondrococcus columnaris was also isolated from Berry Creek water. This myxobacterium can be distinguished from the other aquatic myxobacteria on the basis of its unique colony morphology. This strain of C. columnaris proved to be one of the common serological types found in the Pacific Northwest. Based on the results obtained thus far, it is possible to speculate on the role of myxobacteria in the freshwater environment. All of the myxobacteria isolated in this study are capable of decomposing complex materials, it seems likely therefore, that these organisms may be active in the decomposition of such complex organic compounds, including the remains of other bacterial cells, which are present in the aquatic habitat. Since the isolates studied are also able to utilize the nutrients present at low levels in the stream water, these myxobacteria are not dependent on macromolecular substrates. Myxobacteria with these abilities are apparently well adapted to the aquatic environment. Close

• 4116. [Article] Genesis of the El Salvador porphyry copper deposit, Chile and distribution of epithermal alteration at Lassen Peak, California

  The El Salvador porphyry copper deposit in the Indio Muerto district of northern Chile has been geologically investigated for more than 60 years and provides one of the best bases for understanding similar ...

  Citation × Citation Citation Abstract Copy Title: Genesis of the El Salvador porphyry copper deposit, Chile and distribution of epithermal alteration at Lassen Peak, California Author: Lee, Robert G. (Robert George) The El Salvador porphyry copper deposit in the Indio Muerto district of northern Chile has been geologically investigated for more than 60 years and provides one of the best bases for understanding similar environments of ore formation elsewhere in the world. Fourteen new zircon U/Pb isotopic ages obtained via in situ SHRIMP-RG analysis are here coupled with previous geological studies to allow refinement of the timing of Eocene porphyry magma emplacement responsible for copper and molybdenum mineralization that occurs in several ore bodies within the district. The earliest intrusions are rhyolites that crop out throughout the district, but are more abundant in the north. In contrast, the later granodiorite porphyries were emplaced only in the central and southern parts of the district. Two age periods of mineralization have been documented using zircon U/Pb geochronology. The low grade and small copper deposit at Old Camp in the northern district is associated with a quartz porphyry intrusion that yielded an age of 43.6 ± 0.5 Ma, whereas the main copper molybdenum deposit at Turquoise Gulch is associated with emplacement of the granodioritic L porphyry plug that yielded an age of 42.0 ± 0.5 Ma. The final intrusion is a series of latite porphyry dikes, which post-date ores and yielded a U/Pb zircon age of 41.6 ± 0.5 Ma. Inherited Eocene zircons with ages from ~45 Ma to ~47 Ma are found within younger porphyry intrusions and likely formed via magmatic recycling of older intrusions. Therefore, the zircon U/Pb ages suggest magmatism spanned approximately 5 million years from 47 to 42 Ma, with hydrothermal copper-molybdenum ores dominantly forming during the final stages of porphyry emplacement. Geochemical analyses by XRF, ICP-MS, electron microprobe and laser-ablation ICP-MS define a wide range of major, minor and trace element contents for the Eocene porphyry intrusions within the district. The early rhyolite and quartz porphyry intrusions have rare earth contents with strong negative europium anomalies and relatively low Sr/Y and Sm/Yb ratios consistent formation via fractional crystallization of plagioclase-rich mineral assemblages from more mafic parental melts. The granodiorite porphyries have no europium anomalies and a wide range of Sr/Y and Sm/Yb ratios that support an origin via fractional crystallization of garnet, hornblende ± titanite, and minor plagioclase from an andesitic parental melt. The granodiorite intrusions at M Gulch – Copper Hill are ~1 m.y. older than and have less evolved trace element ratios than the younger granodiorite intrusions associated with the main mineralization event. The evolving Eocene intrusions are the result of lower to middle crust melts ascending to mix with silica-rich differentiated melts derived from fractional crystallization of older andesitic magmas. Progressive decrease of Eu/Eu* ratios in the zircons with decreasing age gives direct evidence in support of the hypothesis that the main ore mineralization is directly related to the evolution of the upper crustal magma reservoir to progressively more oxidized conditions. A second goal of this study was to document the mineralogy and zonation of altered wall rock at Lassen National Volcanic Park in northern California, in order to understand the pressure, temperature, fluid composition, and epithermal processes along the southern flank of Lassen Peak. Extensive epithermal wall rock alteration occurs along the southern flank of the Cascadia volcano and includes both active and fossil geothermal systems. Geologic mapping coupled with mineral identification using a portable infrared spectrometer and X-ray diffraction outline several hydrothermal systems within the park. Currently active, steam-heated acid sulfate alteration is characterized by kaolinite, alunite, opal, and cristobalite with accessory iron sulfates. The active hydrothermal zones are proximal to thermal pools and fumaroles at Sulphur Works, Pilot Pinnacle, Little Hot Springs Valley, and Bumpass Hell. At least three fossil systems occur within andesite lavas and flow breccias of the eroded Pleistocene Brokeoff Volcano. Intermediate argillic alteration occurs at higher elevations on the flanks of the eroded volcano and is characterized by mixed layer illite-smectite, quartz, pyrite, and albite. Propylitic alteration occurs within the eroded lower elevations of Little Hot Springs Valley and is characterized by chlorite, calcite, quartz, pyrite, illite, albite, and rare epidote. Also present to a lesser extent is an advanced argillic alteration defined by pyrophyllite, dickite, alunite, kaolinite, and quartz formed at Pilot Pinnacle. Title: Genesis of the El Salvador porphyry copper deposit, Chile and distribution of epithermal alteration at Lassen Peak, California Author: Lee, Robert G. (Robert George) The El Salvador porphyry copper deposit in the Indio Muerto district of northern Chile has been geologically investigated for more than 60 years and provides one of the best bases for understanding similar environments of ore formation elsewhere in the world. Fourteen new zircon U/Pb isotopic ages obtained via in situ SHRIMP-RG analysis are here coupled with previous geological studies to allow refinement of the timing of Eocene porphyry magma emplacement responsible for copper and molybdenum mineralization that occurs in several ore bodies within the district. The earliest intrusions are rhyolites that crop out throughout the district, but are more abundant in the north. In contrast, the later granodiorite porphyries were emplaced only in the central and southern parts of the district. Two age periods of mineralization have been documented using zircon U/Pb geochronology. The low grade and small copper deposit at Old Camp in the northern district is associated with a quartz porphyry intrusion that yielded an age of 43.6 ± 0.5 Ma, whereas the main copper molybdenum deposit at Turquoise Gulch is associated with emplacement of the granodioritic L porphyry plug that yielded an age of 42.0 ± 0.5 Ma. The final intrusion is a series of latite porphyry dikes, which post-date ores and yielded a U/Pb zircon age of 41.6 ± 0.5 Ma. Inherited Eocene zircons with ages from ~45 Ma to ~47 Ma are found within younger porphyry intrusions and likely formed via magmatic recycling of older intrusions. Therefore, the zircon U/Pb ages suggest magmatism spanned approximately 5 million years from 47 to 42 Ma, with hydrothermal copper-molybdenum ores dominantly forming during the final stages of porphyry emplacement. Geochemical analyses by XRF, ICP-MS, electron microprobe and laser-ablation ICP-MS define a wide range of major, minor and trace element contents for the Eocene porphyry intrusions within the district. The early rhyolite and quartz porphyry intrusions have rare earth contents with strong negative europium anomalies and relatively low Sr/Y and Sm/Yb ratios consistent formation via fractional crystallization of plagioclase-rich mineral assemblages from more mafic parental melts. The granodiorite porphyries have no europium anomalies and a wide range of Sr/Y and Sm/Yb ratios that support an origin via fractional crystallization of garnet, hornblende ± titanite, and minor plagioclase from an andesitic parental melt. The granodiorite intrusions at M Gulch – Copper Hill are ~1 m.y. older than and have less evolved trace element ratios than the younger granodiorite intrusions associated with the main mineralization event. The evolving Eocene intrusions are the result of lower to middle crust melts ascending to mix with silica-rich differentiated melts derived from fractional crystallization of older andesitic magmas. Progressive decrease of Eu/Eu* ratios in the zircons with decreasing age gives direct evidence in support of the hypothesis that the main ore mineralization is directly related to the evolution of the upper crustal magma reservoir to progressively more oxidized conditions. A second goal of this study was to document the mineralogy and zonation of altered wall rock at Lassen National Volcanic Park in northern California, in order to understand the pressure, temperature, fluid composition, and epithermal processes along the southern flank of Lassen Peak. Extensive epithermal wall rock alteration occurs along the southern flank of the Cascadia volcano and includes both active and fossil geothermal systems. Geologic mapping coupled with mineral identification using a portable infrared spectrometer and X-ray diffraction outline several hydrothermal systems within the park. Currently active, steam-heated acid sulfate alteration is characterized by kaolinite, alunite, opal, and cristobalite with accessory iron sulfates. The active hydrothermal zones are proximal to thermal pools and fumaroles at Sulphur Works, Pilot Pinnacle, Little Hot Springs Valley, and Bumpass Hell. At least three fossil systems occur within andesite lavas and flow breccias of the eroded Pleistocene Brokeoff Volcano. Intermediate argillic alteration occurs at higher elevations on the flanks of the eroded volcano and is characterized by mixed layer illite-smectite, quartz, pyrite, and albite. Propylitic alteration occurs within the eroded lower elevations of Little Hot Springs Valley and is characterized by chlorite, calcite, quartz, pyrite, illite, albite, and rare epidote. Also present to a lesser extent is an advanced argillic alteration defined by pyrophyllite, dickite, alunite, kaolinite, and quartz formed at Pilot Pinnacle. Close

• 4117. [Article] Impact of yeast present during pre-fermentation cold maceration on Pinot noir wine aroma

  This research investigated yeast populations and diversity during pre-fermentation cold maceration and alcoholic fermentation of Vitis vinifera L. cv. Pinot noir grapes from a commercial vineyard (Dayton, ...

  Citation × Citation Citation Abstract Copy Title: Impact of yeast present during pre-fermentation cold maceration on Pinot noir wine aroma Author: Hall, Harper L. This research investigated yeast populations and diversity during pre-fermentation cold maceration and alcoholic fermentation of Vitis vinifera L. cv. Pinot noir grapes from a commercial vineyard (Dayton, OR). Fermentations were conducted at the Oregon State University research winery in 100 L tanks while grapes from the same vineyard lot were fermented at a commercial winery. Samples were taken daily during pre-fermentation maceration (9°C) and alcoholic fermentation (27°C) and plated on WL and lysine media to determine Saccharomyces and non-Saccharomyces populations and diversity. Total non-Saccharomyces populations increased from 1 x 10³ cfu/mL to 1 x 10⁵ cfu/mL during pre-fermentation cold maceration and reached a maximum of 1 x 10⁷ cfu/mL during alcoholic fermentation. Thirteen distinct yeast species were tentatively identified based on appearance on WL media and were initially screened for β-glucosidase activity using 4-methyllumbelliferyl-β-D-gluconopyranoside (4-MUG) plates. The identity of the isolates screening positive for β-glucosidase activity was determined by sequence analysis of the D1/D2 domain of the 26S rDNA gene. The five isolates identified were Metschnikowia pulcherrima, Hanseniaspora uvarum, Kluveromyces thermotolerans, and two Saccharomyces cerevisiae isolates. β-glucosidase activity was further characterized and quantified using a liquid media representing grape must conditions (pH 3.5, 20° Brix) at two temperatures (25°C and 8°C). While increasing sugar concentration suppressed the β-glucosidase activity of H. uvarum (-99%), β-glucosidase activity still remained relatively high for M. pulcherrima, S. cerevisiae isolate 1, and S. cerevisiae isolate 2. At 8°C, β-glucosidase activity was reduced for M. pulcherrima compared to activity at 25°C, but activity increased for K. thermotolerans, S. cerevisiae isolate 1, and S. cerevisiae isolate 2. The yeast isolates possessing β-glucosidase activity were used in fermentations of Vitis vinifera L. cv. Pinot Noir grapes. The grapes were treated with high hydrostatic pressure (HHP) to inactivate naturally occurring yeast and bacteria. All yeast isolates grew during pre-fermentation cold maceration (7 days at 9°C) and populations increased 3 to 4 logs. Following pre-fermentation cold maceration, all ferments were warmed to 27°C and inoculated with S. cerevisiae RC212. Alcoholic fermentations were all complete within eight days and after pressing wines were analyzed for volatile aroma compounds by SPME-GC-MS. The presence of different yeast isolates during pre-fermentation cold maceration resulted in wines with unique aroma profiles. Ethyl ester concentrations were highest in the wine that did not undergo a pre-fermentation cold maceration, while concentrations of branch-chained esters were higher in the treatments with yeast present during pre-fermentation cold maceration. Pre-fermentation cold maceration with yeast isolates demonstrating β-glucosidase did not affect the concentration of β-damascenone or β-ionone. Wines that had undergone pre-fermentation cold maceration with S. cerevisiae isolate 1, S. cerevisiae isolate 2, and a combination of all isolates resulted in over twice the concentration of β-citronellol over wines that did not undergo a pre-fermentation cold maceration. Title: Impact of yeast present during pre-fermentation cold maceration on Pinot noir wine aroma Author: Hall, Harper L. This research investigated yeast populations and diversity during pre-fermentation cold maceration and alcoholic fermentation of Vitis vinifera L. cv. Pinot noir grapes from a commercial vineyard (Dayton, OR). Fermentations were conducted at the Oregon State University research winery in 100 L tanks while grapes from the same vineyard lot were fermented at a commercial winery. Samples were taken daily during pre-fermentation maceration (9°C) and alcoholic fermentation (27°C) and plated on WL and lysine media to determine Saccharomyces and non-Saccharomyces populations and diversity. Total non-Saccharomyces populations increased from 1 x 10³ cfu/mL to 1 x 10⁵ cfu/mL during pre-fermentation cold maceration and reached a maximum of 1 x 10⁷ cfu/mL during alcoholic fermentation. Thirteen distinct yeast species were tentatively identified based on appearance on WL media and were initially screened for β-glucosidase activity using 4-methyllumbelliferyl-β-D-gluconopyranoside (4-MUG) plates. The identity of the isolates screening positive for β-glucosidase activity was determined by sequence analysis of the D1/D2 domain of the 26S rDNA gene. The five isolates identified were Metschnikowia pulcherrima, Hanseniaspora uvarum, Kluveromyces thermotolerans, and two Saccharomyces cerevisiae isolates. β-glucosidase activity was further characterized and quantified using a liquid media representing grape must conditions (pH 3.5, 20° Brix) at two temperatures (25°C and 8°C). While increasing sugar concentration suppressed the β-glucosidase activity of H. uvarum (-99%), β-glucosidase activity still remained relatively high for M. pulcherrima, S. cerevisiae isolate 1, and S. cerevisiae isolate 2. At 8°C, β-glucosidase activity was reduced for M. pulcherrima compared to activity at 25°C, but activity increased for K. thermotolerans, S. cerevisiae isolate 1, and S. cerevisiae isolate 2. The yeast isolates possessing β-glucosidase activity were used in fermentations of Vitis vinifera L. cv. Pinot Noir grapes. The grapes were treated with high hydrostatic pressure (HHP) to inactivate naturally occurring yeast and bacteria. All yeast isolates grew during pre-fermentation cold maceration (7 days at 9°C) and populations increased 3 to 4 logs. Following pre-fermentation cold maceration, all ferments were warmed to 27°C and inoculated with S. cerevisiae RC212. Alcoholic fermentations were all complete within eight days and after pressing wines were analyzed for volatile aroma compounds by SPME-GC-MS. The presence of different yeast isolates during pre-fermentation cold maceration resulted in wines with unique aroma profiles. Ethyl ester concentrations were highest in the wine that did not undergo a pre-fermentation cold maceration, while concentrations of branch-chained esters were higher in the treatments with yeast present during pre-fermentation cold maceration. Pre-fermentation cold maceration with yeast isolates demonstrating β-glucosidase did not affect the concentration of β-damascenone or β-ionone. Wines that had undergone pre-fermentation cold maceration with S. cerevisiae isolate 1, S. cerevisiae isolate 2, and a combination of all isolates resulted in over twice the concentration of β-citronellol over wines that did not undergo a pre-fermentation cold maceration. Close

• 4118. [Article] Investigation of Chain Extension Approaches for the Stereoselective Reagent-Controlled Synthesis of alpha-Heteroatom Substituted Alkyl Boronic Esters

  Two distinct strategies were explored for the enantioselective synthesis of α-heteroatom substituted alkyl boronic esters by stereoselective reagent-controlled homologation using transient chiral carbenoid ...

  Citation × Citation Citation Abstract Copy Title: Investigation of Chain Extension Approaches for the Stereoselective Reagent-Controlled Synthesis of alpha-Heteroatom Substituted Alkyl Boronic Esters Author: Barsamian, Adam L. Two distinct strategies were explored for the enantioselective synthesis of α-heteroatom substituted alkyl boronic esters by stereoselective reagent-controlled homologation using transient chiral carbenoid reagents CHYMX (Y = heteroatom, X = nucleofuge, M = electrofuge). In the first case, a stereospecific reagent-controlled homologation (sStReCH) approach to α-alkoxyalkylboronates using α-metalated S,O- and O,O-acetals was pursued that necessitated the development of methods to access these carbenoids in stereodefined form and study of their configurational and chemical stability (both classes of carbenoid are known to chain extend alkyl boronic esters). Sulfoxide-metal exchange from dithioorthoformate monooxides was evaluated as a means to access stereodefined α-metalated S,O-acetals. It was discovered that acyclic dithioorthoformate monooxides fragment spontaneously upon their oxidative generation from simple dithioorthoformates [(pTolS)₂CHOR, R = Me, Et]; however, two cyclic dithioorthoformate monooxides, trans and cis 2-isopentoxy-1,3-benzodithiolane-S-oxide (102), were obtained in 85% yield (trans:cis = 96:4) by 3-chloroperoxybenzoic acid mediated oxidation of 2-isopentoxy-1,3-benzodithiolane. Treatment of trans or cis-102 with EtMgCl (in THF at -78 °C) gave configurationally stable (≤ 2.5 h, at -78 °C) stereodefined α-magnesiated S,O-acetals 103 that incorporated D-atoms in a stereospecific manner upon reaction with CD3OD. Carbenoids 103 (M = MgCl) failed to react with all other electrophiles examined (allyl bromide, MeI, MeOTf), except benzaldehyde, and this low nucleophilicity precluded their use in boronic ester chain extension chemistry. α-Lithiated S,O-acetals 103 generated in the same fashion from 102 using PhLi were more reactive than their magnesiated congeners 103 but lacked sufficient configurational stability for applications in sStReCH (epimerization of 103 (M = Li) occurred within 1 min at -78 °C in THF). Direct metalation approaches to stereodefined lithiated S,O- and O,O-acetals were next explored, but ultimately, either acceptably high enantioselectivity was not realized or the organolithiums generated were found to be too chemically unstable for sStReCH applications. For example, kinetic enantioselective lithiation of methoxymethyl p-tolyl thioether (124) with s-butyllithium/(-)-sparteine (PhMe, -78 °C) followed by treatment of the resulting lithiated S,O-acetal [pTolSCH(Li)OMe] with benzaldehyde as a probe electrophile, led to addition products [pTolSCH(OMe)CH(OH)Ph] with low enantiomeric excess [55% yield, dr = 66:34, %ee (major isomer) = 24%, %ee (minor isomer) = 9%]. In another example, lithiation of a thiocarbamate of methoxymethyl mercaptan [i-Pr₂NC(=S)SCH₂OMe] with s-butyllithium and TMEDA (Et₂O, -110 °C) led to a chemically unstable carbenoid that spontaneously extruded methyl thioformate (MeOCHS) to yield putative a-lithio-N,N-diisopropylthioformamide [i-Pr₂NC(=S)Li]. The second strategy explored, and introduced here for the first time, ligand mediated stereoinductive reagent-controlled homologation (iStReCH), deliberately exploits the configurational lability of heteroatom substituted carbenoids and consequently it was more successful. In this case, dynamic kinetic resolution (DKR), or dynamic thermodynamic resolution (DTR), of a racemic configurationally labile carbenoid is effected by an exogenous chiral ligand as the carbenoid is trapped by the boronic ester electrophile. The iStReCH concept was demonstrated for an enantioselective synthesis of α-silylalkylboronates, as follows: (±)-lithio(dimethylphenylsilyl)methyl 2,4,6-triisopropylbenzoate [TIBOCH(Li)SiMe₂Ph], obtained by lithiation of the corresponding silylmethyl TIB ester with t-butyllithium (cumene, -78 °C), was incubated with the chiral BOX ligand 2,2-bis[(4S)-4,5-dihydro-4-isopropyloxazol-2-yl)propane (at -45 °C) before addition of B-phenethyl pinacol boronate at -95 °C. Warming to rt during 18 hours afforded the desired enantioenriched chain extended product (S)-2-[1-(dimethylphenylsilyl)-3-phenylpropyl]-4,4,5,5- tetramethyl-1,3,2-dioxaborolane (69% yield, 57% ee). Ligand mediated iStReCH of B-cyclohexyl (35% yield, 9% ee) and B-sec-butyl [43% yield, dr = 58:42, %ee (major) = 26%, %ee (minor) = 14%] pinacol boronates with the same silylated carbenoid was likewise demonstrated. Enantioselectivity was dependent on the temperature history of the organolithium/ligand complex indicating that the stereoinduction mechanism involves some aspect of DTR. Title: Investigation of Chain Extension Approaches for the Stereoselective Reagent-Controlled Synthesis of alpha-Heteroatom Substituted Alkyl Boronic Esters Author: Barsamian, Adam L. Two distinct strategies were explored for the enantioselective synthesis of α-heteroatom substituted alkyl boronic esters by stereoselective reagent-controlled homologation using transient chiral carbenoid reagents CHYMX (Y = heteroatom, X = nucleofuge, M = electrofuge). In the first case, a stereospecific reagent-controlled homologation (sStReCH) approach to α-alkoxyalkylboronates using α-metalated S,O- and O,O-acetals was pursued that necessitated the development of methods to access these carbenoids in stereodefined form and study of their configurational and chemical stability (both classes of carbenoid are known to chain extend alkyl boronic esters). Sulfoxide-metal exchange from dithioorthoformate monooxides was evaluated as a means to access stereodefined α-metalated S,O-acetals. It was discovered that acyclic dithioorthoformate monooxides fragment spontaneously upon their oxidative generation from simple dithioorthoformates [(pTolS)₂CHOR, R = Me, Et]; however, two cyclic dithioorthoformate monooxides, trans and cis 2-isopentoxy-1,3-benzodithiolane-S-oxide (102), were obtained in 85% yield (trans:cis = 96:4) by 3-chloroperoxybenzoic acid mediated oxidation of 2-isopentoxy-1,3-benzodithiolane. Treatment of trans or cis-102 with EtMgCl (in THF at -78 °C) gave configurationally stable (≤ 2.5 h, at -78 °C) stereodefined α-magnesiated S,O-acetals 103 that incorporated D-atoms in a stereospecific manner upon reaction with CD3OD. Carbenoids 103 (M = MgCl) failed to react with all other electrophiles examined (allyl bromide, MeI, MeOTf), except benzaldehyde, and this low nucleophilicity precluded their use in boronic ester chain extension chemistry. α-Lithiated S,O-acetals 103 generated in the same fashion from 102 using PhLi were more reactive than their magnesiated congeners 103 but lacked sufficient configurational stability for applications in sStReCH (epimerization of 103 (M = Li) occurred within 1 min at -78 °C in THF). Direct metalation approaches to stereodefined lithiated S,O- and O,O-acetals were next explored, but ultimately, either acceptably high enantioselectivity was not realized or the organolithiums generated were found to be too chemically unstable for sStReCH applications. For example, kinetic enantioselective lithiation of methoxymethyl p-tolyl thioether (124) with s-butyllithium/(-)-sparteine (PhMe, -78 °C) followed by treatment of the resulting lithiated S,O-acetal [pTolSCH(Li)OMe] with benzaldehyde as a probe electrophile, led to addition products [pTolSCH(OMe)CH(OH)Ph] with low enantiomeric excess [55% yield, dr = 66:34, %ee (major isomer) = 24%, %ee (minor isomer) = 9%]. In another example, lithiation of a thiocarbamate of methoxymethyl mercaptan [i-Pr₂NC(=S)SCH₂OMe] with s-butyllithium and TMEDA (Et₂O, -110 °C) led to a chemically unstable carbenoid that spontaneously extruded methyl thioformate (MeOCHS) to yield putative a-lithio-N,N-diisopropylthioformamide [i-Pr₂NC(=S)Li]. The second strategy explored, and introduced here for the first time, ligand mediated stereoinductive reagent-controlled homologation (iStReCH), deliberately exploits the configurational lability of heteroatom substituted carbenoids and consequently it was more successful. In this case, dynamic kinetic resolution (DKR), or dynamic thermodynamic resolution (DTR), of a racemic configurationally labile carbenoid is effected by an exogenous chiral ligand as the carbenoid is trapped by the boronic ester electrophile. The iStReCH concept was demonstrated for an enantioselective synthesis of α-silylalkylboronates, as follows: (±)-lithio(dimethylphenylsilyl)methyl 2,4,6-triisopropylbenzoate [TIBOCH(Li)SiMe₂Ph], obtained by lithiation of the corresponding silylmethyl TIB ester with t-butyllithium (cumene, -78 °C), was incubated with the chiral BOX ligand 2,2-bis[(4S)-4,5-dihydro-4-isopropyloxazol-2-yl)propane (at -45 °C) before addition of B-phenethyl pinacol boronate at -95 °C. Warming to rt during 18 hours afforded the desired enantioenriched chain extended product (S)-2-[1-(dimethylphenylsilyl)-3-phenylpropyl]-4,4,5,5- tetramethyl-1,3,2-dioxaborolane (69% yield, 57% ee). Ligand mediated iStReCH of B-cyclohexyl (35% yield, 9% ee) and B-sec-butyl [43% yield, dr = 58:42, %ee (major) = 26%, %ee (minor) = 14%] pinacol boronates with the same silylated carbenoid was likewise demonstrated. Enantioselectivity was dependent on the temperature history of the organolithium/ligand complex indicating that the stereoinduction mechanism involves some aspect of DTR. Close

• 4119. [Article] Nitrogen and heavy metal distribution in soils utilized as sludge disposal sites

  Metropolitan areas today must dispose large volumes of sewage sludge produced during the wastewater treatment process. This research was conducted to study the effect of large applications of municipal ...

  Citation × Citation Citation Abstract Copy Title: Nitrogen and heavy metal distribution in soils utilized as sludge disposal sites Author: Prothero, Gary Lewis Metropolitan areas today must dispose large volumes of sewage sludge produced during the wastewater treatment process. This research was conducted to study the effect of large applications of municipal sewage sludge on (a) the distribution of N and trace elements (Cd, Cr, Cu, Mn, Ni, Zn) in the soil profile, (b) the uptake of these elements by plants growing on the sludge-treated soil, and (c) the potential for groundwater contamination. Five sludge disposal sites in the Willamette Valley were selected for the project, Milwaukie, Eugene, Hillsboro, Forest Grove, and Woodburn, Oregon. The soils were sampled quarterly, July, 1974, December, March, and June, 1975, as a function of depth. Surface soil samples (8 to 10 cores) were collected in September, 1974, from each disposal location to determine the uniformity and amount of sludge applied. Plant samples from the disposal area and water samples from wells adjacent to each area were also collected. The soil, plant, water, and sludge samples were analyzed for total N, NH₄-N, NO3-N, Cd, Cr, Cu, Mn, Ni, and Zn; the water, plant, and sludges were also analyzed for P. The soil samples collected during the winter, spring, and summer, 1975, were analyzed for NH₄-N and NO₃-N. An estimated 500, 290, 96, 72, and 20 dry m tons /ha of sludge were applied to the Eugene, Hillsboro, Forest Grove, Woodburn, and Milwaukie disposal areas, respectively. The total N and P content of the five sludges ranged from 3.9 to 6. 3% and 0.5 to 2. 9%, respectively. The inorganic N was primarily in the form of NH₄-N. The trace element (Cd, Cr, Cu, Mn, Ni, Zn) content of the sewage sludge fell within general ranges reported for municipal sludges, except for the Cr content (17, 700 ppm) of the Milwaukie sludge. The Cd, Cr, Cu, Ni, Zn, NH₄-N, NO₃-N, and total N content increased in the surface soil of each sludge disposal area. The Cd, Cr, Cu, Mn, Ni, Zn, NH₄-N and total N content of the treated soils compared closely to the control soils below 50 cm in the soil profile suggesting restricted movement of heavy metals. The NO₃-N content in the soil profile increased with the sludge application rate. The NO₃-N level of the Eugene and Hillsboro disposal areas was as high as 120 and 20 ppm, respectively. During the winter and spring, 1975, increased rainfall and cooler temperatures combined to decrease the NO₃-N content in the surface soil and increase NO₃-N levels in the lower soil horizons. The pH of the surface soil at the Eugene and Hillsboro disposal areas decreased from pH values of 6.4 to 4.6 and pH 4.8 to 4.4, respectively, a result of the nitrification reaction. The pH values of the other disposal areas compared closely to the control soil. The N and Zn content of the grass growing on the sludge-treated areas increased at the high sludge application rate compared to the grasses growing in the control area. The Cd, Cr, Cu, Mn, Ni, and P concentration increased in the grass sampled from the Eugene disposal area, while the Cd, Cr, Cu, Mn, Ni, and P content of grasses from the other sludge - treated areas compared more closely to the grasses from the control areas. The lower pH at the Eugene disposal area and the high sludge application rate combined to enhance the trace element uptake by plants. The NO₃-N, NH₄-N, P, Cd, Cr, Cu, Mn, Ni, and Zn content in the water samples from the Eugene, Milwaukie, Forest Grove, and Woodburn disposal areas were below the Public Health Service drinking water limits. The long-term disposal of municipal sewage sludges on agricultural land appears to be a viable waste disposal method, providing the sludge application rate and metal content are not excessively high. In any land disposal program for sewage sludge, the heavy metal accumulation in the soil surface and plants growing in the sludge-treated soil should be monitored. Title: Nitrogen and heavy metal distribution in soils utilized as sludge disposal sites Author: Prothero, Gary Lewis Metropolitan areas today must dispose large volumes of sewage sludge produced during the wastewater treatment process. This research was conducted to study the effect of large applications of municipal sewage sludge on (a) the distribution of N and trace elements (Cd, Cr, Cu, Mn, Ni, Zn) in the soil profile, (b) the uptake of these elements by plants growing on the sludge-treated soil, and (c) the potential for groundwater contamination. Five sludge disposal sites in the Willamette Valley were selected for the project, Milwaukie, Eugene, Hillsboro, Forest Grove, and Woodburn, Oregon. The soils were sampled quarterly, July, 1974, December, March, and June, 1975, as a function of depth. Surface soil samples (8 to 10 cores) were collected in September, 1974, from each disposal location to determine the uniformity and amount of sludge applied. Plant samples from the disposal area and water samples from wells adjacent to each area were also collected. The soil, plant, water, and sludge samples were analyzed for total N, NH₄-N, NO3-N, Cd, Cr, Cu, Mn, Ni, and Zn; the water, plant, and sludges were also analyzed for P. The soil samples collected during the winter, spring, and summer, 1975, were analyzed for NH₄-N and NO₃-N. An estimated 500, 290, 96, 72, and 20 dry m tons /ha of sludge were applied to the Eugene, Hillsboro, Forest Grove, Woodburn, and Milwaukie disposal areas, respectively. The total N and P content of the five sludges ranged from 3.9 to 6. 3% and 0.5 to 2. 9%, respectively. The inorganic N was primarily in the form of NH₄-N. The trace element (Cd, Cr, Cu, Mn, Ni, Zn) content of the sewage sludge fell within general ranges reported for municipal sludges, except for the Cr content (17, 700 ppm) of the Milwaukie sludge. The Cd, Cr, Cu, Ni, Zn, NH₄-N, NO₃-N, and total N content increased in the surface soil of each sludge disposal area. The Cd, Cr, Cu, Mn, Ni, Zn, NH₄-N and total N content of the treated soils compared closely to the control soils below 50 cm in the soil profile suggesting restricted movement of heavy metals. The NO₃-N content in the soil profile increased with the sludge application rate. The NO₃-N level of the Eugene and Hillsboro disposal areas was as high as 120 and 20 ppm, respectively. During the winter and spring, 1975, increased rainfall and cooler temperatures combined to decrease the NO₃-N content in the surface soil and increase NO₃-N levels in the lower soil horizons. The pH of the surface soil at the Eugene and Hillsboro disposal areas decreased from pH values of 6.4 to 4.6 and pH 4.8 to 4.4, respectively, a result of the nitrification reaction. The pH values of the other disposal areas compared closely to the control soil. The N and Zn content of the grass growing on the sludge-treated areas increased at the high sludge application rate compared to the grasses growing in the control area. The Cd, Cr, Cu, Mn, Ni, and P concentration increased in the grass sampled from the Eugene disposal area, while the Cd, Cr, Cu, Mn, Ni, and P content of grasses from the other sludge - treated areas compared more closely to the grasses from the control areas. The lower pH at the Eugene disposal area and the high sludge application rate combined to enhance the trace element uptake by plants. The NO₃-N, NH₄-N, P, Cd, Cr, Cu, Mn, Ni, and Zn content in the water samples from the Eugene, Milwaukie, Forest Grove, and Woodburn disposal areas were below the Public Health Service drinking water limits. The long-term disposal of municipal sewage sludges on agricultural land appears to be a viable waste disposal method, providing the sludge application rate and metal content are not excessively high. In any land disposal program for sewage sludge, the heavy metal accumulation in the soil surface and plants growing in the sludge-treated soil should be monitored. Close

• 4120. [Article] Physiological effects of water stress on young corn plants

  Laboratory experiments were used to investigate the mechanism of plant response to water stress by determining the sensitivity of leaf elongation, photosynthesis and transpiration in young corn plants ...

  Citation × Citation Citation Abstract Copy Title: Physiological effects of water stress on young corn plants Author: Barlow, Edward William Ross Laboratory experiments were used to investigate the mechanism of plant response to water stress by determining the sensitivity of leaf elongation, photosynthesis and transpiration in young corn plants to a decrease in leaf water potential. In initial experiments, 9 day old corn plants were grown at soil water potentials of -0.35 and -2.50 bars for 6 days using the polyethylene glycol semi-permeable membrane technique of controlling soil water potential. Leaf elongation and soluble carbohydrate content were found to be more sensitive to a reduction in soil water potential than net assimilation and transpiration. Lowering the soil water potential from -0.35 to -2.50 bars resulted in a 44 percent decrease in the rate of leaf elongation and a 42 percent increase in the soluble carbohydrate content of the plant, while the rates of net assimilation and transpiration were reduced by 26 and 24 percent respectively. The differing sensitivity of leaf elongation and photosynthesis to decreasing soil water potential was examined in detail in subsequent experiments by simultaneously monitoring the rates of net photosynthesis, transpiration, and leaf elongation and the leaf water potential of a young corn plant as it became water stressed. Leaf elongation ceased at a leaf water potential of -9 to -9.5 bars, whereas the rates of net photosynthesis and transpiration were not reduced significantly until the leaf water potential reached -12 to -13 bars. The sharp decrease in rate of net photosynthesis in the vicinity of -12 to -13 bars was due to increases in both the stomatal and mesophyll resistances to CO₂ transfer. It was concluded that the decreases in the rate of net photosynthesis due to water stress were caused by stomatal and nonstomatal effects of approximately equal magnitude. The nonstomatal or intracellular factors responsible for the decrease in the rate of net photosynthesis were not identified. It was hypothesized that the differing sensitivity of leaf elongation and photosynthesis to water stress, may result in the accumulation of photosynthate within a mildly water stressed plant. This mechanism was demonstrated in experiments where the soluble carbohydrate content of the top 3 leaves of a mildly stressed corn plant was shown to be significantly higher than in the corresponding leaves of a nonstressed control plant after a 6 hour stress period. This increase in the soluble carbohydrate content of the mildly stressed plant was accompanied by a significant decrease in the net photosynthetic rate of this plant. A similar response was obtained when leaf elongation rate was reduced by lowering the temperature of the apical meristem. The results were interpreted as evidence for the operation of a source-sink type control mechanism of photosynthesis in mildly stressed plants. The effect of water potential on the elongation rate, the adenylate energy charge, ATP content and free amino acid content of the youngest unrolled leaf of a 6 leaf corn plant was examined in a final series of experiments. These experiments sought to determine whether the decrease in photosynthate utilization, observed when cell expansion was limited by water stress, was due to a simple product inhibition feedback mechanism or to the direct effect of water stress on some aspect of cell metabolism. The ATP content of the elongating cells was found to be as sensitive as leaf elongation to small changes in leaf water potential. Adenylate energy charge did decrease with leaf water potential, but was not as sensitive as the ATP content to changes in leaf water potential. The free amino acid level was found to increase at leaf water potentials lower than -10 bars, and this may indicate that the inhibition of protein synthesis during water stress may be due to the deficiency of chemical energy within the cell. It was concluded that during water stress, the biosynthetic activity of elongating cells may be limited by a low level of available energy in the form of ATP. This decreased synthesis of ATP may be due to a direct effect of water stress on respiration and ATP formation. The sensitivity of leaf enlargement to mild water stress and its subsequent effect on photosynthesis indicates that plant growth and production may be limited by mild stress in the field situation. The vegetative growth of plants depends on both the photosynthetic rate and the rate of increase of the photosynthetic surface area. The response of leaf enlargement to water stress in the field therefore warrants thorough further investigation. Title: Physiological effects of water stress on young corn plants Author: Barlow, Edward William Ross Laboratory experiments were used to investigate the mechanism of plant response to water stress by determining the sensitivity of leaf elongation, photosynthesis and transpiration in young corn plants to a decrease in leaf water potential. In initial experiments, 9 day old corn plants were grown at soil water potentials of -0.35 and -2.50 bars for 6 days using the polyethylene glycol semi-permeable membrane technique of controlling soil water potential. Leaf elongation and soluble carbohydrate content were found to be more sensitive to a reduction in soil water potential than net assimilation and transpiration. Lowering the soil water potential from -0.35 to -2.50 bars resulted in a 44 percent decrease in the rate of leaf elongation and a 42 percent increase in the soluble carbohydrate content of the plant, while the rates of net assimilation and transpiration were reduced by 26 and 24 percent respectively. The differing sensitivity of leaf elongation and photosynthesis to decreasing soil water potential was examined in detail in subsequent experiments by simultaneously monitoring the rates of net photosynthesis, transpiration, and leaf elongation and the leaf water potential of a young corn plant as it became water stressed. Leaf elongation ceased at a leaf water potential of -9 to -9.5 bars, whereas the rates of net photosynthesis and transpiration were not reduced significantly until the leaf water potential reached -12 to -13 bars. The sharp decrease in rate of net photosynthesis in the vicinity of -12 to -13 bars was due to increases in both the stomatal and mesophyll resistances to CO₂ transfer. It was concluded that the decreases in the rate of net photosynthesis due to water stress were caused by stomatal and nonstomatal effects of approximately equal magnitude. The nonstomatal or intracellular factors responsible for the decrease in the rate of net photosynthesis were not identified. It was hypothesized that the differing sensitivity of leaf elongation and photosynthesis to water stress, may result in the accumulation of photosynthate within a mildly water stressed plant. This mechanism was demonstrated in experiments where the soluble carbohydrate content of the top 3 leaves of a mildly stressed corn plant was shown to be significantly higher than in the corresponding leaves of a nonstressed control plant after a 6 hour stress period. This increase in the soluble carbohydrate content of the mildly stressed plant was accompanied by a significant decrease in the net photosynthetic rate of this plant. A similar response was obtained when leaf elongation rate was reduced by lowering the temperature of the apical meristem. The results were interpreted as evidence for the operation of a source-sink type control mechanism of photosynthesis in mildly stressed plants. The effect of water potential on the elongation rate, the adenylate energy charge, ATP content and free amino acid content of the youngest unrolled leaf of a 6 leaf corn plant was examined in a final series of experiments. These experiments sought to determine whether the decrease in photosynthate utilization, observed when cell expansion was limited by water stress, was due to a simple product inhibition feedback mechanism or to the direct effect of water stress on some aspect of cell metabolism. The ATP content of the elongating cells was found to be as sensitive as leaf elongation to small changes in leaf water potential. Adenylate energy charge did decrease with leaf water potential, but was not as sensitive as the ATP content to changes in leaf water potential. The free amino acid level was found to increase at leaf water potentials lower than -10 bars, and this may indicate that the inhibition of protein synthesis during water stress may be due to the deficiency of chemical energy within the cell. It was concluded that during water stress, the biosynthetic activity of elongating cells may be limited by a low level of available energy in the form of ATP. This decreased synthesis of ATP may be due to a direct effect of water stress on respiration and ATP formation. The sensitivity of leaf enlargement to mild water stress and its subsequent effect on photosynthesis indicates that plant growth and production may be limited by mild stress in the field situation. The vegetative growth of plants depends on both the photosynthetic rate and the rate of increase of the photosynthetic surface area. The response of leaf enlargement to water stress in the field therefore warrants thorough further investigation. Close