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Title: The effects of wind and shaking on the morphology, growth, gas exchange and water relations of Pinus contorta Douglas
Author: Rees, David
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1979
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(1) Subjecting two year old Pinus contorta to high winds in a controlled environment wind tunnel, or to continuous shaking by a specially constructed shaking rig, caused a 20% reduction in extension growth of leader and lateral stems. Rates of needle extension were reduced 11% by shaking and 30% by exposure to high wind. Radial growth of the stem was not affected. (2) Lacroscopic investigation of cell size and number revealed that the reduced growth of leader stems was due primarily to a reduction in cell division. Cell extension was also slightly reduced. (3) The reduced extension growth caused by shaking was accompanied by large reductions in dry weight. Relative Growth Rate and Unit Leaf Rate were reduced, but Leaf Area Ratio was unaffected; suggesting that the reduced growth was due to a decrease in net photosynthesis, or to an increase in dark respiration. (4) Subjecting P. contorta to high winds had no effect on pet photosynthesis, determined with an Infra-Red Gas Analyser, but significantly increased dark respiration. (5) t'hole-plant and detached-needle transpiration rates were determined gravimetrically. High winds and shaking had no effect on stomatal or cuticular conductances. Total water potential, determined with a needle pressure-bomb, was slightly increased by wind and shaking. Solute and pressure potentials of individual needles, determined by the pressure-voltuae technique, were not affected. It is concluded that mechanical stress does not affect the growth of P. contorta via an effect on water relations. (6) It is postulated that mechanical stress causes an increase in 'maintenance respiration', with a resultant decrease in respiratory substrate for growth. The consequent reduction in cell division and extension leads to a decrease in extension growth and dry weight growth. It is accepted that the links between these various processes are unclear.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available