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• 1. [Article] The effects of low temperatures on dormancy release in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) from western Oregon, Washington, and California

  The effect of low temperatures given at different times and duration upon the time of bud burst, shoot elongation, number of needles developed and needle length in Douglas-fir plants from the Oregon Cascades ...

  Citation × Citation Citation Abstract Copy Title: The effects of low temperatures on dormancy release in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) from western Oregon, Washington, and California Author: Sugano, Albert Itsuki The effect of low temperatures given at different times and duration upon the time of bud burst, shoot elongation, number of needles developed and needle length in Douglas-fir plants from the Oregon Cascades and three coastal areas ranging from Washington to California were determined. The plants were grown outside in a lathhouse then chilled at 11-day intervals with three temperatures. These treatment combinations were applied early and late in the dormant period. The most effective temperature treatment was 40°F followed by 45° and 50° F, in that order. All three temperatures hastened bud burst for the plants from low elevation as length of chilling increased; however, 45° and 50°F was ineffective when chilling was expanded from 33 to 44 days for the high elevation. If chilling is done early a longer period is required to break dormancy than if done late during the dormant period. Delay of chilling also increased shoot elongation and the number of needles developed remained fairly constant, altering only the needles per centimeter. Title: The effects of low temperatures on dormancy release in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) from western Oregon, Washington, and California Author: Sugano, Albert Itsuki The effect of low temperatures given at different times and duration upon the time of bud burst, shoot elongation, number of needles developed and needle length in Douglas-fir plants from the Oregon Cascades and three coastal areas ranging from Washington to California were determined. The plants were grown outside in a lathhouse then chilled at 11-day intervals with three temperatures. These treatment combinations were applied early and late in the dormant period. The most effective temperature treatment was 40°F followed by 45° and 50° F, in that order. All three temperatures hastened bud burst for the plants from low elevation as length of chilling increased; however, 45° and 50°F was ineffective when chilling was expanded from 33 to 44 days for the high elevation. If chilling is done early a longer period is required to break dormancy than if done late during the dormant period. Delay of chilling also increased shoot elongation and the number of needles developed remained fairly constant, altering only the needles per centimeter. Close

• 2. [Article] The economic feasibility of preheating Douglas-fir blocks prior to peeling

  Past research and industrial sources have implied that preheating Douglas-fir Pseudotsuga menziesii (Mirb.) Franco prior to peeling veneer was economically feasible. To test this, the effect of treatment ...

  Citation × Citation Citation Abstract Copy Title: The economic feasibility of preheating Douglas-fir blocks prior to peeling Author: Baskin, Richard Past research and industrial sources have implied that preheating Douglas-fir Pseudotsuga menziesii (Mirb.) Franco prior to peeling veneer was economically feasible. To test this, the effect of treatment temperature on veneer yield and thickness variation for three diameter classes of low grade Douglas-fir logs was studied and related to the cost of preheating. Test results showed that pre-heating No. 3 Douglas-fir Sawmill logs to a peel temperature range of 50°F to 120°F had no statistical effect on veneer value, total yield, grade yield, or veneer sheet width yield of 12, 18, and 24 inch diameter blocks. Block diameter, however was found to have a highly significant effect on veneer value expressed as the value of the percentage of the block volume recovered as marketable green veneer. Eighteen inch diameter blocks had the greatest total, grade, and full sheet recovery per unit volume of initial block diameter. Twenty-four inch diameter blocks had the least recovery and value while the 12 inch blocks were intermediate. Veneer thickness variation was found to be independent of peel temperature but significantly influenced by block diameter. The reason for the block diameter-veneer yield and thickness variation interaction was not investigated but was probably due to a complex interaction of wood properties at various diameters and the changing in the lathe setting angles due to the differences between diameters. A microprocessor based data acquisition system was built to record the output of a non-contact infrared temperature sensing instrument that measured the block temperature profile during peeling. The variability of temperature found within the blocks suggest the effects of heating would vary greatly for any one block. The microprocessor proved to be a valuable research tool that has many research uses but more importantly, many industrial process control applications. The equation describing unsteady state transfer for an infinitely long cylinder was solved via numerical analysis to theoretically estimate heating times for veneer blocks. The model may not be applicable to wood because the assumptions used to solve the problem, i.e. constant diffusivity and homogenity of the material, are violated when dealing with wood. Title: The economic feasibility of preheating Douglas-fir blocks prior to peeling Author: Baskin, Richard Past research and industrial sources have implied that preheating Douglas-fir Pseudotsuga menziesii (Mirb.) Franco prior to peeling veneer was economically feasible. To test this, the effect of treatment temperature on veneer yield and thickness variation for three diameter classes of low grade Douglas-fir logs was studied and related to the cost of preheating. Test results showed that pre-heating No. 3 Douglas-fir Sawmill logs to a peel temperature range of 50°F to 120°F had no statistical effect on veneer value, total yield, grade yield, or veneer sheet width yield of 12, 18, and 24 inch diameter blocks. Block diameter, however was found to have a highly significant effect on veneer value expressed as the value of the percentage of the block volume recovered as marketable green veneer. Eighteen inch diameter blocks had the greatest total, grade, and full sheet recovery per unit volume of initial block diameter. Twenty-four inch diameter blocks had the least recovery and value while the 12 inch blocks were intermediate. Veneer thickness variation was found to be independent of peel temperature but significantly influenced by block diameter. The reason for the block diameter-veneer yield and thickness variation interaction was not investigated but was probably due to a complex interaction of wood properties at various diameters and the changing in the lathe setting angles due to the differences between diameters. A microprocessor based data acquisition system was built to record the output of a non-contact infrared temperature sensing instrument that measured the block temperature profile during peeling. The variability of temperature found within the blocks suggest the effects of heating would vary greatly for any one block. The microprocessor proved to be a valuable research tool that has many research uses but more importantly, many industrial process control applications. The equation describing unsteady state transfer for an infinitely long cylinder was solved via numerical analysis to theoretically estimate heating times for veneer blocks. The model may not be applicable to wood because the assumptions used to solve the problem, i.e. constant diffusivity and homogenity of the material, are violated when dealing with wood. Close

• 3. [Article] Temperature effects on the growth of Douglas-fir seedlings

  This study was undertaken to determine the effects of different chilling treatments during the dormant season upon growth of Douglas-fir seedlings0 In addition it was planned to determine whether seedlings native ...

  Citation × Citation Citation Abstract Copy Title: Temperature effects on the growth of Douglas-fir seedlings Author: Wommack, Donald Everett This study was undertaken to determine the effects of different chilling treatments during the dormant season upon growth of Douglas-fir seedlings0 In addition it was planned to determine whether seedlings native to various geographic areas differ in their chilling requirements0 The hypotheses were advanced, based on previous studies, that chilling at near L&00F. was more effective in satisfying the chilling requirement of plants than chilling at temperatures near 32°F., or 50°F., and that plants native to areas of low elevation, characterized by mild winters, require less chilling than plants native to areas of high elevation characterized by long and severe winters. Verification or rejection of these hypotheses was undertaken by subjecting dormant seedlings of Douglas-fir, native to several geographic areas, to chilling under different temperature treatments for different lengths of time. Experiment I was designed to compare the effects of chilling for three, six, and twelve weeks at various temperatures (32, L&0, 50, and 60°F., and out-of-doors) on two-year-old seedlings from eight geographic areas. After chilling, they were moved to a warm greenhouse and exposed to short days (nine hours). The effectiveness of the treatments in breaking dormancy was expressed in number of days from end of treatment to bud burst, percentage of plants which broke dormancy, and amount of shoot elongation. In general 40°F. was the most effective treatment followed by 32°F., out-of-doors, 50, and 60°F., in that order. The latter temperature had little or no effect in breaking dormancy compared with the other treatments. Twelve weeks of chilling were more effective than chilling for shorter periods at all temperatures except 60°F. At six weeks 40°F. was the most effective treatment, 32°F. was less effective, while 50, 60°F., and out-of- doors treatments were ineffective in breaking dormancy. Four weeks of chilling were ineffective regardless of the chilling treatment. Genetic differences were observed among the plants from the eight areas chilled at 40°F. for twelve weeks. Plants native to the highest areas represented in the experiment resumed growth earlier than those from the lower elevations. Experiments II and III differed from Experiment I since the dormant seedlings had germinated and grown only about three months prior to chilling. In these experiments plants were chilled for four, eight, and twelve weeks. After the chilling period half of the plants were grown under long days (normal days plus two hours of artificial light) while the other half were maintained on short days (nine hours). The results of Experiment II were similar to those of Experiment I with respect to the greater effectiveness of 40°F. compared with the other temperature8. Long days seemed to compensate for lack of adequate chilling except in plants chilled for twelve weeks at 40°F., indicating that the chilling requirements of these plants had been more adequately satisfied than by any of the other treatments. Experiment III was designed to compare the effectiveness of chilling under fluctuating day and night temperatures with that of chilling at a constant temperature. Fluctuating day and night temperatures of 40/32°F. (40°F. day, 32'F. night) were about as effective as continuous chilling at 32°F. or 40°F. Fluctuating temperatures of 50/32°F., and 50/40°F. appeared to be about as effective as continuous chilling at 50°F. Chilling at 50°F. during the day, irrespective of the temperature during night, delayed bud burst in comparison with chilling at 32, 40, or 40/32°F. Genetic differences were observed among the plants from the different areas in Experiments II and 1110 Plants native to high elevations (6000' elev.) resumed growth in lower percentages, resumed growth later, and grew less than plants from tower elevations (3000' and 3600' elev.). The principal contribution of this study has been the demonstration of differences in effectiveness of several chilling treatments in breaking the dormancy of seedlings. Variations in the chilling requirements of seedlings native to different areas has also been shown. Title: Temperature effects on the growth of Douglas-fir seedlings Author: Wommack, Donald Everett This study was undertaken to determine the effects of different chilling treatments during the dormant season upon growth of Douglas-fir seedlings0 In addition it was planned to determine whether seedlings native to various geographic areas differ in their chilling requirements0 The hypotheses were advanced, based on previous studies, that chilling at near L&00F. was more effective in satisfying the chilling requirement of plants than chilling at temperatures near 32°F., or 50°F., and that plants native to areas of low elevation, characterized by mild winters, require less chilling than plants native to areas of high elevation characterized by long and severe winters. Verification or rejection of these hypotheses was undertaken by subjecting dormant seedlings of Douglas-fir, native to several geographic areas, to chilling under different temperature treatments for different lengths of time. Experiment I was designed to compare the effects of chilling for three, six, and twelve weeks at various temperatures (32, L&0, 50, and 60°F., and out-of-doors) on two-year-old seedlings from eight geographic areas. After chilling, they were moved to a warm greenhouse and exposed to short days (nine hours). The effectiveness of the treatments in breaking dormancy was expressed in number of days from end of treatment to bud burst, percentage of plants which broke dormancy, and amount of shoot elongation. In general 40°F. was the most effective treatment followed by 32°F., out-of-doors, 50, and 60°F., in that order. The latter temperature had little or no effect in breaking dormancy compared with the other treatments. Twelve weeks of chilling were more effective than chilling for shorter periods at all temperatures except 60°F. At six weeks 40°F. was the most effective treatment, 32°F. was less effective, while 50, 60°F., and out-of- doors treatments were ineffective in breaking dormancy. Four weeks of chilling were ineffective regardless of the chilling treatment. Genetic differences were observed among the plants from the eight areas chilled at 40°F. for twelve weeks. Plants native to the highest areas represented in the experiment resumed growth earlier than those from the lower elevations. Experiments II and III differed from Experiment I since the dormant seedlings had germinated and grown only about three months prior to chilling. In these experiments plants were chilled for four, eight, and twelve weeks. After the chilling period half of the plants were grown under long days (normal days plus two hours of artificial light) while the other half were maintained on short days (nine hours). The results of Experiment II were similar to those of Experiment I with respect to the greater effectiveness of 40°F. compared with the other temperature8. Long days seemed to compensate for lack of adequate chilling except in plants chilled for twelve weeks at 40°F., indicating that the chilling requirements of these plants had been more adequately satisfied than by any of the other treatments. Experiment III was designed to compare the effectiveness of chilling under fluctuating day and night temperatures with that of chilling at a constant temperature. Fluctuating day and night temperatures of 40/32°F. (40°F. day, 32'F. night) were about as effective as continuous chilling at 32°F. or 40°F. Fluctuating temperatures of 50/32°F., and 50/40°F. appeared to be about as effective as continuous chilling at 50°F. Chilling at 50°F. during the day, irrespective of the temperature during night, delayed bud burst in comparison with chilling at 32, 40, or 40/32°F. Genetic differences were observed among the plants from the different areas in Experiments II and 1110 Plants native to high elevations (6000' elev.) resumed growth in lower percentages, resumed growth later, and grew less than plants from tower elevations (3000' and 3600' elev.). The principal contribution of this study has been the demonstration of differences in effectiveness of several chilling treatments in breaking the dormancy of seedlings. Variations in the chilling requirements of seedlings native to different areas has also been shown. Close

• 4. [Article] Impacts of nursery processing on the survival, growth and physiology of 2+0 Douglas-fir seedlings

  This study compared three nursery handling processes from the time just before lifting to the time seedlings are placed in cold storage after grading, sorting, and packing at the nursery. The seedlings ...

  Citation × Citation Citation Abstract Copy Title: Impacts of nursery processing on the survival, growth and physiology of 2+0 Douglas-fir seedlings Author: Darbyshire, Robyn Lea Willey This study compared three nursery handling processes from the time just before lifting to the time seedlings are placed in cold storage after grading, sorting, and packing at the nursery. The seedlings handled in these different ways were compared first in terms of the temperature and plant moisture stresses they experienced during nursery handling. A second study of their growth and survival in a plantation and in an irrigation experiment was undertaken. The three treatments were: (1) conventional nursery handling with seedlings held for 48 hours in a cool, humid room (about 40°F and 80-90% relative humidity) between lifting and grading; (2) conventional nursery handling with seedlings held outdoors on a covered dock for 48 hours between lifting and grading; (3) bedpacking, where seedlings are lifted and taken directly to cold storage without the extra help handling involved in grading, sorting, and packing. The comparison of different temperature and plant moisture stress at the nursery showed no difference in plant moisture stress (PMS) during the holding period for treatments (1) and (2). Treatment (1) however did keep the seedlings at a lower temperature than (2). Treatment (3) had the lowest PMS and temperature during the holding period. Seedlings planted in a plowed field in a split-plot design showed no significant differences in budbreak, rate of height growth, or survival due to handling treatment after one growing season, but bedpack seedlings showed significantly larger (p=0.01) new terminal length and dry weight than the other two treatments. Though not significant, the same trend occurred for dry weight of new laterals and total shoot dry weight. Seedlings planted in the irrigation study showed significant differences in budbreak, height growth, survival, and final morphology due primarily to the level of irrigation. More work at different nurseries and in different outplanting environments is needed before strong recommendations can be made about bedpacking versus conventional handling. Greater attention to the management of temperature and plant moisture stress during nursery handling may eliminate differences between conventional handling and bedpacking. Title: Impacts of nursery processing on the survival, growth and physiology of 2+0 Douglas-fir seedlings Author: Darbyshire, Robyn Lea Willey This study compared three nursery handling processes from the time just before lifting to the time seedlings are placed in cold storage after grading, sorting, and packing at the nursery. The seedlings handled in these different ways were compared first in terms of the temperature and plant moisture stresses they experienced during nursery handling. A second study of their growth and survival in a plantation and in an irrigation experiment was undertaken. The three treatments were: (1) conventional nursery handling with seedlings held for 48 hours in a cool, humid room (about 40°F and 80-90% relative humidity) between lifting and grading; (2) conventional nursery handling with seedlings held outdoors on a covered dock for 48 hours between lifting and grading; (3) bedpacking, where seedlings are lifted and taken directly to cold storage without the extra help handling involved in grading, sorting, and packing. The comparison of different temperature and plant moisture stress at the nursery showed no difference in plant moisture stress (PMS) during the holding period for treatments (1) and (2). Treatment (1) however did keep the seedlings at a lower temperature than (2). Treatment (3) had the lowest PMS and temperature during the holding period. Seedlings planted in a plowed field in a split-plot design showed no significant differences in budbreak, rate of height growth, or survival due to handling treatment after one growing season, but bedpack seedlings showed significantly larger (p=0.01) new terminal length and dry weight than the other two treatments. Though not significant, the same trend occurred for dry weight of new laterals and total shoot dry weight. Seedlings planted in the irrigation study showed significant differences in budbreak, height growth, survival, and final morphology due primarily to the level of irrigation. More work at different nurseries and in different outplanting environments is needed before strong recommendations can be made about bedpacking versus conventional handling. Greater attention to the management of temperature and plant moisture stress during nursery handling may eliminate differences between conventional handling and bedpacking. Close

• 5. [Article] Lethal surface temperatures and their interpretation for Douglas-fir

  Citation × Citation Citation Abstract Copy Title: Lethal surface temperatures and their interpretation for Douglas-fir Author: Silen, Roy R. Title: Lethal surface temperatures and their interpretation for Douglas-fir Author: Silen, Roy R. Close

• 6. [Article] Comparative photosynthesis and respiration rates of Douglas-fir seedlings from Vancouver Island and Montana under various conditions of light and temperature

  Citation × Citation Citation Abstract Copy Title: Comparative photosynthesis and respiration rates of Douglas-fir seedlings from Vancouver Island and Montana under various conditions of light and temperature Author: Krueger, Kenneth W. Title: Comparative photosynthesis and respiration rates of Douglas-fir seedlings from Vancouver Island and Montana under various conditions of light and temperature Author: Krueger, Kenneth W. Close

• 7. [Article] Photosynthesis, respiration, and dry matter accumulation of Douglas-fir seedlings from different geographic sources and growth at different temperatures

  Citation × Citation Citation Abstract Copy Title: Photosynthesis, respiration, and dry matter accumulation of Douglas-fir seedlings from different geographic sources and growth at different temperatures Author: Sorensen, Frank C. Title: Photosynthesis, respiration, and dry matter accumulation of Douglas-fir seedlings from different geographic sources and growth at different temperatures Author: Sorensen, Frank C. Close

• 8. [Article] Physiological control of fine root turnover in Douglas-fir

  To determine whether shading increases drought-induced root mortality by changing the chemical composition of roots, I conducted an experiment in which high and low light treatments in combination with ...

  Citation × Citation Citation Abstract Copy Title: Physiological control of fine root turnover in Douglas-fir Author: Marshall, John D. (John David), 1956- To determine whether shading increases drought-induced root mortality by changing the chemical composition of roots, I conducted an experiment in which high and low light treatments in combination with high and low soil moisture treatments were applied to seedlings of Douglas-fir (Pseudotsuqa menziesii Mirb. Franco). Because synthesis of suberin (a water-repellent compound found in roots) is metabolically expensive, I hypothesized that suberin synthesis might be reduced in roots of a shade-stressed tree and thereby, susceptibility to desiccation would be increased. As expected, the drying treatments increased root mortality for the shaded seedlings, however, no differences in suberization were found. I measured starch and sugar concentrations of the roots and found that carbohydrate reserves of roots in the shaded treatments were nearly exhausted. I concluded that root mortality induced by shading and drought was probably caused by depletion of carbohydrate reserves in the root rather than by differences in resistance to desiccation. I then set up an experiment to determine whether accumulation and depletion of carbohydrate reserves were indeed the physiological mechanisms underlying fine root turnover. Douglas-fir seedlings were grown at soil temperatures of 10°C, 20°C, and 30°C, at uniform air temperatures, with and without light. It was necessary to develop a starch extraction procedure using 35% perchloric acid in order to consistently extract all starch from the tissue. Sequential harvests were weighed and analyzed for starch and sugars. Starch reserves were exhausted in the roots of the dark-grown seedlings at all temperatures and were also exhausted in the roots of the light-grown seedlings at 20°C and 30°C. In the light-grown seedlings from the 10°C treatment, however, significant accumulations of starch were observed in association with pulses of root growth. Based on this study and on others from Sweden and from Oregon, I suggest that root lifetimes may be determined by the amount of starch with which a newly grown root is endowed and the rate at which this starch supply is respired. A simple means of estimating root biomass production and turnover based on root starch and soil temperature is described. Title: Physiological control of fine root turnover in Douglas-fir Author: Marshall, John D. (John David), 1956- To determine whether shading increases drought-induced root mortality by changing the chemical composition of roots, I conducted an experiment in which high and low light treatments in combination with high and low soil moisture treatments were applied to seedlings of Douglas-fir (Pseudotsuqa menziesii Mirb. Franco). Because synthesis of suberin (a water-repellent compound found in roots) is metabolically expensive, I hypothesized that suberin synthesis might be reduced in roots of a shade-stressed tree and thereby, susceptibility to desiccation would be increased. As expected, the drying treatments increased root mortality for the shaded seedlings, however, no differences in suberization were found. I measured starch and sugar concentrations of the roots and found that carbohydrate reserves of roots in the shaded treatments were nearly exhausted. I concluded that root mortality induced by shading and drought was probably caused by depletion of carbohydrate reserves in the root rather than by differences in resistance to desiccation. I then set up an experiment to determine whether accumulation and depletion of carbohydrate reserves were indeed the physiological mechanisms underlying fine root turnover. Douglas-fir seedlings were grown at soil temperatures of 10°C, 20°C, and 30°C, at uniform air temperatures, with and without light. It was necessary to develop a starch extraction procedure using 35% perchloric acid in order to consistently extract all starch from the tissue. Sequential harvests were weighed and analyzed for starch and sugars. Starch reserves were exhausted in the roots of the dark-grown seedlings at all temperatures and were also exhausted in the roots of the light-grown seedlings at 20°C and 30°C. In the light-grown seedlings from the 10°C treatment, however, significant accumulations of starch were observed in association with pulses of root growth. Based on this study and on others from Sweden and from Oregon, I suggest that root lifetimes may be determined by the amount of starch with which a newly grown root is endowed and the rate at which this starch supply is respired. A simple means of estimating root biomass production and turnover based on root starch and soil temperature is described. Close

• 9. [Article] The effects of some soaking treatments on the germination of Douglas-fir seed

  The Oregon State Cooperative Seed laboratory uses two methods for testing the quality of Douglas-fir seed lots. The first of these is a straight-forward germination test without any pre-treatment of the ...

  Citation × Citation Citation Abstract Copy Title: The effects of some soaking treatments on the germination of Douglas-fir seed Author: Leahy, Peter Michael The Oregon State Cooperative Seed laboratory uses two methods for testing the quality of Douglas-fir seed lots. The first of these is a straight-forward germination test without any pre-treatment of the seed, involving a period of 42 days in the germinator at alternating 20°C.-30°C. temperatures. The second method consists of 14 days pre-chill of the seed on the moistened medium at 5°C. prior to 28 days germination at the same alternating temperatures. The pre-chill helps to overcome dormancy which may be present in the lots. Recent work by several investigators has indicated that soaking pre-treatments might also be employed to overcome dormancy in coniferous seed. The study was designed to evaluate some of these soaking treatments in relation to the methods at present used by the laboratory. In all cases soaking was followed by pre-chilling; so that a measure of additional effects of the soaking treatment on the dormant seed was obtained. Two studies were made with the normal laboratory testing methods as controls. The first consisted of soaking the seed in water at temperatures of 5°C., 20°C. and 30°C. for periods of 12, 24, 36 and 48 hours, prior to pre-chill and germination. In the second study soaking temperatures of 5°C. for 36 hours and 30°C. for 14 hours were used. The seed was soaked in water and in 0.2 percent potassium nitrate solution , to determine the merits of the two soaking media. At 5°C. the effect of light during the soaking was examined together with its effect during pre-chilling on the germination of seed soaked at both temperatures. Included in the thesis are the results of a small study designed to determine an effective and reliable method of estimating moisture content in the soaked seed. Consequently moisture content was determined on an over-dry weight basis after heating the soaked seed at 100°C. for six hours in an air-oven. Three seed lots were used in an attempt to obtain results over a wide range of seed quality. As demonstrated by the germination figures, the lots chosen exhibited such a range. Though the lots responded differently to the treatments employed, no over-all increase in germination of the dormant seed present was obtained with any of the treatments. The 30°C. soaking for the longer periods produced a considerable decline in the germination, germinative capacity and germinative energy of the lots. Dormancy was present in two of the three lots, but the number of dormant seeds remained approximately constant over all the treatments. Dormancy was reduced only in the case of the pre-chilled controls over the controls without pre-chill. The statistical analysis of the germination percentages revealed that temperatures of soaking was the dominant factor affecting germination. The period of soaking, though influencing the moisture content attained, was of little consequence in germination. No responses were obtained with the use of light during soaking and pre-chill, nor with the variation in soaking medium. A convariance analysis of moisture content attained and subsequent germination, indicated the absence of any correlation between the two entities. Taken as a whole, soaking procedures are of no advantage over the present germination techniques in use at the Oregon State Laboratory for Douglas-fir tree seed. Title: The effects of some soaking treatments on the germination of Douglas-fir seed Author: Leahy, Peter Michael The Oregon State Cooperative Seed laboratory uses two methods for testing the quality of Douglas-fir seed lots. The first of these is a straight-forward germination test without any pre-treatment of the seed, involving a period of 42 days in the germinator at alternating 20°C.-30°C. temperatures. The second method consists of 14 days pre-chill of the seed on the moistened medium at 5°C. prior to 28 days germination at the same alternating temperatures. The pre-chill helps to overcome dormancy which may be present in the lots. Recent work by several investigators has indicated that soaking pre-treatments might also be employed to overcome dormancy in coniferous seed. The study was designed to evaluate some of these soaking treatments in relation to the methods at present used by the laboratory. In all cases soaking was followed by pre-chilling; so that a measure of additional effects of the soaking treatment on the dormant seed was obtained. Two studies were made with the normal laboratory testing methods as controls. The first consisted of soaking the seed in water at temperatures of 5°C., 20°C. and 30°C. for periods of 12, 24, 36 and 48 hours, prior to pre-chill and germination. In the second study soaking temperatures of 5°C. for 36 hours and 30°C. for 14 hours were used. The seed was soaked in water and in 0.2 percent potassium nitrate solution , to determine the merits of the two soaking media. At 5°C. the effect of light during the soaking was examined together with its effect during pre-chilling on the germination of seed soaked at both temperatures. Included in the thesis are the results of a small study designed to determine an effective and reliable method of estimating moisture content in the soaked seed. Consequently moisture content was determined on an over-dry weight basis after heating the soaked seed at 100°C. for six hours in an air-oven. Three seed lots were used in an attempt to obtain results over a wide range of seed quality. As demonstrated by the germination figures, the lots chosen exhibited such a range. Though the lots responded differently to the treatments employed, no over-all increase in germination of the dormant seed present was obtained with any of the treatments. The 30°C. soaking for the longer periods produced a considerable decline in the germination, germinative capacity and germinative energy of the lots. Dormancy was present in two of the three lots, but the number of dormant seeds remained approximately constant over all the treatments. Dormancy was reduced only in the case of the pre-chilled controls over the controls without pre-chill. The statistical analysis of the germination percentages revealed that temperatures of soaking was the dominant factor affecting germination. The period of soaking, though influencing the moisture content attained, was of little consequence in germination. No responses were obtained with the use of light during soaking and pre-chill, nor with the variation in soaking medium. A convariance analysis of moisture content attained and subsequent germination, indicated the absence of any correlation between the two entities. Taken as a whole, soaking procedures are of no advantage over the present germination techniques in use at the Oregon State Laboratory for Douglas-fir tree seed. Close

• 10. [Article] Freezing resistance of tissues in the twig of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco)

  The relative freezing resistance of tissues in the stem, foliage and buds of terminal twigs from Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was investigated at about ten-day intervals from summer ...

  Citation × Citation Citation Abstract Copy Title: Freezing resistance of tissues in the twig of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) Author: Alden, John Norman The relative freezing resistance of tissues in the stem, foliage and buds of terminal twigs from Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was investigated at about ten-day intervals from summer until the following spring. Tissues from growing twigs collected before development of dormancy had no freezing resistance and were killed immediately after subcooling. Tissues at the base of inner bud scales and in the pith of stems at the base of buds were among the last to harden in autumn. Pith parenchyma and pith rays of the interfascicular region of the bud trace and the transfusion tissue in needles were most susceptible to injury after development of freezing resistance. Abaxial mesophyll was more susceptible to injury than adaxial mesophyll of hardened needles. The cortex was more resistant than other tissues during development of freezing resistance but parenchyma of the pith lost freezing resistance more slowly and was more resistant after growth processes resumed in the spring. The phloem-cambium region of the stem lost freezing resistance earlier and became more susceptible to injury than other tissues of the twig after midwinter0 Survival of the vegetative apex depended on the ability of its water to subcool. Heat of fusion of water on freezing produced a sharp exotherm that was a precise index of the temperature at death and freezing resistance of the vegetative apex. Prolonged subfreezing temperatures after development of freezing resistance in late autumn increased hardiness of twigs beyond that induced by the natural environment6 Both formation of ice in the pith of stems enclosed by coriaceous bud scales, and artificial dehydration reduced water content and promoted subcooling and freezing resistance of vegetative apices. Moisture content was reduced from 200 to 70 percent on a dry weight basis after three days at _90 C in early February and freezing resistance of apices increased 0 0 0 from -16 C to -20 C when cooled at 1 C per minute0 These findings suggested that diffusion of water from the protoplasm to sites of extracellular ice, and not low temperature, was the direct cause of hardening at subfreezing temperatures0 The basic freezing curve for Douglas-fir is characteristic of plant tissues in general but was modified by exotherms associated with freezing and death of vegetative apices from November until April. A decline n length of the plateau after the second subcooling temperature during hardening, and increase in length of the plateau during loss of hardiness reflected probable seasonal change in quantity of intracellular water. Unhardened tissues survived freezing of extracellular water but were injured before intracellular water was completely frozen. Hardened tissues, on the other hand, were not injured until after most of the intracellular water was frozen and the cooling rate of the stem returned to normal. Observations suggested a definite relationship between time of acquisition and loss of freezing resistance and number of days to bud burst after March 31. Trees which developed freezing resistance earliest in fall broke buds earliest in spring. Trees which broke buds latest in spring were also those which were the last to deharden, Ready availability of potassium appears to enhance early development and loss of freezing resistance. Trees with the highest content of potassium in the current season's foliage burst buds earliest and those with the lowest content of potassium were the last to burst buds. Night temperatures of 20 C delayed but did not prevent loss of hardiness when day temperatures were 250 C in March. However, continuous temperature of 2° C failed to reharden twigs that had lost freezing resistance at 25° C. Injury to all tissues, except the vegetative apex, declined at 250 C in March when moisture stress exceeded a critical level. These observations suggest that environ mental conditions unfavorable for growth enable Douglas-fir to maintain resistance to injury from spring frosts. Title: Freezing resistance of tissues in the twig of Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) Author: Alden, John Norman The relative freezing resistance of tissues in the stem, foliage and buds of terminal twigs from Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) was investigated at about ten-day intervals from summer until the following spring. Tissues from growing twigs collected before development of dormancy had no freezing resistance and were killed immediately after subcooling. Tissues at the base of inner bud scales and in the pith of stems at the base of buds were among the last to harden in autumn. Pith parenchyma and pith rays of the interfascicular region of the bud trace and the transfusion tissue in needles were most susceptible to injury after development of freezing resistance. Abaxial mesophyll was more susceptible to injury than adaxial mesophyll of hardened needles. The cortex was more resistant than other tissues during development of freezing resistance but parenchyma of the pith lost freezing resistance more slowly and was more resistant after growth processes resumed in the spring. The phloem-cambium region of the stem lost freezing resistance earlier and became more susceptible to injury than other tissues of the twig after midwinter0 Survival of the vegetative apex depended on the ability of its water to subcool. Heat of fusion of water on freezing produced a sharp exotherm that was a precise index of the temperature at death and freezing resistance of the vegetative apex. Prolonged subfreezing temperatures after development of freezing resistance in late autumn increased hardiness of twigs beyond that induced by the natural environment6 Both formation of ice in the pith of stems enclosed by coriaceous bud scales, and artificial dehydration reduced water content and promoted subcooling and freezing resistance of vegetative apices. Moisture content was reduced from 200 to 70 percent on a dry weight basis after three days at _90 C in early February and freezing resistance of apices increased 0 0 0 from -16 C to -20 C when cooled at 1 C per minute0 These findings suggested that diffusion of water from the protoplasm to sites of extracellular ice, and not low temperature, was the direct cause of hardening at subfreezing temperatures0 The basic freezing curve for Douglas-fir is characteristic of plant tissues in general but was modified by exotherms associated with freezing and death of vegetative apices from November until April. A decline n length of the plateau after the second subcooling temperature during hardening, and increase in length of the plateau during loss of hardiness reflected probable seasonal change in quantity of intracellular water. Unhardened tissues survived freezing of extracellular water but were injured before intracellular water was completely frozen. Hardened tissues, on the other hand, were not injured until after most of the intracellular water was frozen and the cooling rate of the stem returned to normal. Observations suggested a definite relationship between time of acquisition and loss of freezing resistance and number of days to bud burst after March 31. Trees which developed freezing resistance earliest in fall broke buds earliest in spring. Trees which broke buds latest in spring were also those which were the last to deharden, Ready availability of potassium appears to enhance early development and loss of freezing resistance. Trees with the highest content of potassium in the current season's foliage burst buds earliest and those with the lowest content of potassium were the last to burst buds. Night temperatures of 20 C delayed but did not prevent loss of hardiness when day temperatures were 250 C in March. However, continuous temperature of 2° C failed to reharden twigs that had lost freezing resistance at 25° C. Injury to all tissues, except the vegetative apex, declined at 250 C in March when moisture stress exceeded a critical level. These observations suggest that environ mental conditions unfavorable for growth enable Douglas-fir to maintain resistance to injury from spring frosts. Close