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Title: The influence of light on the photosynthetic apparatus of Sitka spruce (Picea sitchensis (Bong.) Carr.)
Author: Lewandowska, M.
Awarding Body: University of Aberdeen
Current Institution: University of Aberdeen
Date of Award: 1976
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Abstract:
The aim of this work was to investigate and compare features of the photosynthetic apparatus of Sitka spruce (Picea sitchensis (Bong.) Carr.) in an attempt to elucidate the causes of variation in photosynthetic capacity in different parts of a forest canopy. Shoots from the top of the canopy had much higher photosynthetic capacities than shoots from the bottom of the canopy. The hypotheses were: 1) shoots from different parts of the canopy behave differently because they have adapted to the prevailing light environment, which varied through the canopy, 2) part of the limitation to photosynthetic capacity occurs in the reactions associated with the photosystems. Measurements to test these hypotheses were made on both forest shoots, corresponding to 'sun' shoots (top of the canopy), partially shaded shoots and 'shade' shoots (bottom of the canopy), and plants grown in controlled environment chambers in each of one of four different photon flux densities (where all other environmental variables were constant). Photosystem activity, expressed per unit leaf area, was higher in the high-light-grown plants and 'sun' shoots. Quantum requirements for photosystem activity were higher in high-light-grown plants and 'sun' shoots. Specific leaf area increased and dry weight fraction decreased with decreasing light availability for growth. Chlorophyll content increased and chl a:b ratio decreased with decreasing cultivation light in the controlled environment chamber plants. In the forest the response of chlorophyll content to shading was variable. In 1974 chlorophyll content increased with increasing shading, in 1975 chlorophyll content remained constant. Chlorophyll a:b ratio was constant throughout the canopy in both years. An attempt to measure the chl:P700 ratio was measured so that rates of photosystem activity could be expressed per unit reaction centre. The basis of expression for the results has been shown to be very important and significantly affects the interpretation of the results. The two hypotheses were supported by the data obtained.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.463160  DOI: Not available
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