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  • Author or Editor: Qi-yuan Pan x
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Apple and many other Rosaceae plants translocate sucrose as well as sorbitol. How photosynthates are partitioned between sorbitol and sucrose in the Rosaceae is not understood. This study was designed to examine the effects of elevated air CO2 on partitioning of sorbitol and other soluble sugars in sink and source apple leaves. Young `Gala' apple plants were exposed to the ambient air and 700, 1000, and 1600 μl·liter–1 of CO2 for 8 days under a light intensity of 928 μmol·m–2·s–1 with a 14-h day/10-h night cycle. Sorbitol, sucrose, glucose, and fructose concentration in sink and source leaves were determined by HPLC analysis. In source leaves, sorbitol was significantly increased, while sucrose was decreased as the air CO2 was elevated from 400 to 1600 μl·liter–1. The sorbitol/sucrose ratio varied from 1.31 in air and 2.26 at 1600 μl·liter–1 of CO2. In sink leaves, sorbitol concentration did not vary across the four CO2 levels; however, sucrose was higher at the three super-atmospheric CO2 levels. Our results suggest that increased photosynthesis via elevated CO2 favors photosynthate partitioning into sorbitol rather than sucrose. A mechanism for regulating this partitioning will be discussed.

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