PLANT PHYSIOLOGY , Vol 110, Issue 4 1361-1366, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Photosynthesis and Carbohydrate Partitioning for the C3 Desert Shrub Encelia farinosa under Current and Doubled CO2 Concentrations
H. Zhang and P. S. Nobel
UCLA-DOE Laboratory and Department of Biology, University of California, Los Angeles, California 90024-1786
Changes in photosynthesis (A) and carbohydrate partitioning were studied
for Encelia farinosa, a common C3 desert shrub in the southwestern United
States, after a 3-month exposure to the current or a doubled CO2
concentration (750 [mu]L L-1). A remained unchanged under the current CO2
concentration but decreased during the day under the doubled CO2
concentration, resulting in a 46% enhancement in the early morning, 26% at
midday, and 15% in the late afternoon by the elevated CO2. The decrease
during the day under the doubled CO2 concentration may represent
end-product inhibition, because the sucrose and the starch contents
increased during the day proportionally more than under the current CO2
concentration. The 14CO2 activity in sink leaves was maximal 3 h after
labeling under the doubled and at 5 h under the current CO2 concentration,
indicating faster movement of photosynthate out of source leaves and into
sink tissues under the doubled CO2 concentration, which may have been
responsible for the sustained enhancement in A under the doubled CO2
concentration.