Water relations, gas exchange, and growth responses of Douglas-fir seedlings to stresses associated with transplanting Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/n870zw24q

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  • The goal of this thesis was to determine the physiological mechanisms that link adverse preplanting treatments of Douglas-fir, such as exposure and root pruning, to the phenomenon of transplanting shock. The objective of experiments 1 and 2 was to measure the effect of exposure and pruning on the physiology and growth of seedlings. The objective of experiment 3 was to understand the physiological mechanisms that affect shoot elongation. Two-year-old Douglas-fir seedlings were exposed or root pruned and transplanted on different dates from November through April. Water relations, gas exchange, phenology, and growth were measured during the first-year of establishment. Exposure reduced new root growth. Stomatal conductance decreased regardless of changes in water potential [psi] during the first 2 months. Time of transplanting significantly affected the stress response of seedlings. Exposed April transplants had reduced stem conducting area, probably due to cavitation. After budbreak, exposed April transplants showed reduced midday [psi] and gas exchange, whereas exposed winter transplants had recovered. Seedlings recovered a favorable [psi] and net photosynthesis before shoot elongation ceased. However, exposure caused a reduction in shoot growth and an increase in the root:shoot ratio. Removing 30-50% of the original root volume reduced shoot and root growth. Predawn [psi] remained unaffected by the root pruning treatments during the first 2 months after planting. After budbreak, midday [psi] and gas exchange of root pruned seedlings were low. Root exposure and root pruning decreased shoot [psi] and turgor during elongation of the leader. The reduced turgor did not affect the rate of cell wall hardening as measured by changes in the modulus of elasticity. Changes in cell wall elasticity closely corresponded to the ontogeny of the leader. Current shoots of stressed seedlings did not show osmotic adjustment during the period of low [psi] . Photosynthesis of stressed seedlings decreased during elongation as a result of non-stomatal mechanisms. Reduced terminal elongation induced by preplanting stresses may be caused by a reduction in cell wall extensibility rather than cell wall elasticity as a result of low turgor. Decreased photosynthesis and a higher allocation of resources to roots during establishment may also limit shoot elongation.
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  • description.provenance : Approved for entry into archive by Linda Kathman(linda.kathman@oregonstate.edu) on 2009-03-19T14:26:04Z (GMT) No. of bitstreams: 1 Joseph_Gladwin_1996.pdf: 1409163 bytes, checksum: bcb089ea90bb0895ee7eb3da90c85b1c (MD5)
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