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Are gas exchange responses to resource limitation and defoliation linked to source: sink relationships?


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Pinkard, EA, Eyles, A and O'Grady, AP 2011 , 'Are gas exchange responses to resource limitation and defoliation linked to source: sink relationships?' , Plant, Cell and Environment, vol. 34 , pp. 1652-1665 , doi: 10.1111/j.1365-3040.2011.02361.x.

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Productivity of trees can be affected by limitations in
resources such as water and nutrients, and herbivory.
However, there is little understanding of their interactive
effects on carbon uptake and growth.We hypothesized that:
(1) in the absence of defoliation, photosynthetic rate and
leaf respiration would be governed by limiting resource(s)
and their impact on sink limitation; (2) photosynthetic
responses to defoliation would be a consequence of changing
source:sink relationships and increased availability of
limiting resources; and (3) photosynthesis and leaf respiration
would be adjusted in response to limiting resources and
defoliation so that growth could be maintained. We tested
these hypotheses by examining how leaf photosynthetic
processes, respiration, carbohydrate concentrations and
growth rates of Eucalyptus globulus were influenced by
high or low water and nitrogen (N) availability, and/or
defoliation. Photosynthesis of saplings grown with low
water was primarily sink limited, whereas photosynthetic
responses of saplings grown with low N were suggestive of
source limitation. Defoliation resulted in source limitation.
Net photosynthetic responses to defoliation were linked
to the degree of resource availability, with the largest
responses measured in treatments where saplings were ultimately
source rather than sink limited. There was good
evidence of acclimation to stress, enabling higher rates of C
uptake than might otherwise have occurred.

Item Type: Article
Authors/Creators:Pinkard, EA and Eyles, A and O'Grady, AP
Keywords: carbohydrate; nitrogen; photosynthesis; respiration; water stress.
Journal or Publication Title: Plant, Cell and Environment
ISSN: 0140-7791
DOI / ID Number: 10.1111/j.1365-3040.2011.02361.x
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