Genetic Polymorphism and Physiological Response to Ambiol in Half-sib Families of Black Spruce (Picea Mariana Mill. B.S.P.).
Genetic Polymorphism and Physiological Response to Ambiol in Half-sib Families of Black Spruce (Picea Mariana Mill. B.S.P.).

Author: Klara Vichnevetski

Publisher:

Published: 1999

Total Pages: 0

ISBN-13:

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Genetic polymorphism based on isozyme analysis, growth response to Ambiol (2-methyl-4-dimethylaminomethyl-5-hydroxybenzimidazole dihydrochloride) and antitranspirant properties of Ambiol were studied in 10 half-sib families of black spruce ('Picea mariana' Mill. B.S.P.). Significant stimulation of diameter growth in 4-month old black spruce seedlings was observed after a single pretreatment of seed with Ambiol and was increased by up to 49% compared to control seedling diameter. Ambiol, however, had a very limited effect on height growth of black spruce seedlings. Growth response to Ambiol was under genetic control, and faster growing half-sib families of black spruce were more responsive to diameter growth stimulation by Ambiol compared to slower growing ones. Antitranspirant properties of Ambiol were also studied in 4-month old black spruce seedlings after single pretreatment of seed. Seedlings were subjected to soil drought stress by water withholding under controlled environment conditions in a growth chamber. Ambiol had a greater effect on reducing stomatal conductance and transpiration than photosynthesis, thereby causing an increase of up to 216% in water use efficiency in seedlings subjected to mild drought stress. Physiological response to drought stress was determined to be under genetic control and faster-growing families of black spruce were less sensitive to stress and recovered faster compared to slower-grown ones. Faster-growing, drought tolerant families were more responsive to Ambiol as an antitranspirant. Although Ambiol did not decrease transpiration in severely stressed seedlings, it did accelerate the recovery process in those seedlings. Dose-effect correlation was not linear in Ambiol as a growth promoter and as an antitranspirant. Potential mechanisms involved in plant growth regulation and stress tolerance as a result of Ambiol seed pretreatment are discussed. Genetic polymorphism expressed as isozyme variation was studied in female megagametophytes of 10 black spruce families by means of starch and polyacrylamide gel electrophoreses. Twenty three loci coding for 15 enzyme systems were analyzed. Interfamily variation was observed for mean heterozygosities, mean number of alleles per locus, percentage of polymorphic loci, presence of rare and unique alleles. A strong association was revealed between mean unbiased genetic distance with morphological distance based on diameter growth variation and with physiological distance based on transpiration efficiency during mild drought stress in classes of black spruce families. This suggested that physiological variation in black spruce families was a function of genetic polymorphism. Family mean multilocus heterozygosity estimated in female megagametophytes was associated with growth, drought tolerance and response to Ambiol in 10 families of black spruce seedlings. It thus presented potential as an early selection criterion for fast growth and drought tolerance and a marker for response to Ambiol in conifers.

Physiological Responses of Black Spruce (Picea Mariana (Mill.) B.S.P.) to Climate Change Parameters
Physiological Responses of Black Spruce (Picea Mariana (Mill.) B.S.P.) to Climate Change Parameters

Author: Danielle Alexandra Way

Publisher:

Published: 2008

Total Pages: 396

ISBN-13: 9780494398296

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Black spruce is a dominant North American boreal tree species that has large impacts on high latitude climate and carbon cycling. Growth of black spruce is strongly inhibited in warm years, and climate change may eliminate this species from much of its current range. This thesis addresses how black spruce responds to high growth temperatures, drought stress and CO2 enrichment using greenhouses and growth chambers to vary growth conditions. Elevated temperatures reduced seedling growth and decreased the root to shoot ratio. Despite increased shoot allocation, warm-grown seedlings had smaller canopies and thinner needles with lower nitrogen content than cool-grown seedlings. Elevated growth temperatures reduced day and dark respiration, and photosynthesis. On a leaf nitrogen basis, photosynthesis showed little thermal acclimation, and the lower carbon gain of warm-grown seedlings was largely due to lower nitrogen content. The ratio of photosynthesis to respiration declined linearly with increasing temperature, implying that reduced carbon gain at elevated temperatures limits black spruce growth. Co-limitation of photosynthesis by Rubisco and RuBP regeneration predominated from 10--30°C, with no evidence for Pi regeneration limitations. At high temperatures, photosynthesis appeared to be limited by Rubisco in warm-grown seedlings, but the limitation was unclear in cool-grown seedlings. High growth temperatures increased seedling thermotolerance; heat damage to needles did not occur below 50°C. In response to prolonged drought, declines in the maximum efficiency of photosystem II occurred at a water potential of -2 to -3 MPa, indicating damage to photosynthetic processes. Elevated growing temperatures reduced the water potential that damaged photosystem II from -2 MPa to -2.5 MPa, but caused seedlings to reach a damaging level of drought stress two to three days earlier than cool-grown seedlings. Photosynthetic acclimation to elevated CO2 can occur within 16 days in black spruce seedlings following high CO2 exposure. An exponentially supplied high nutrient treatment did not affect the degree of down-regulation of photosynthesis to high CO2. Exposure to elevated CO2 during the first year of growth did not enhance growth the following year and had little effect on biomass over a five-year field study.