Effect of Oxygen Concentration on 14C-Photoassimilate Transport from Leaves of Salvia splendens L.

Publisher Website
Google Scholar
Abstract
Partitioning and transport of recently fixed photosynthate was examined following 14CO2 pulse-labeling of intact, attached leaves of Salvia splendens L. maintained in an atmosphere of 300 microliters per liter CO2 and 20, 210, or 500 milliliters per liter O2. Under conditions of increasing O2 (210, 500 milliliters per liter), a smaller percentage of the recently fixed 14C in the leaf was allocated to starch, whereas a greater percentage of the fixed 14C appeared in amino acids, particularly serine. The increase in 14C in amino acids was reflected in material exported from source leaves. A higher percentage of 14C in serine, glycine, and glutamate was recovered in petiole extracts when source leaves were maintained under elevated O2 levels. Although pool sizes of these amino acids were increased in both the leaves and petioles with increasing photorespiratory activity, no significant changes in either 14C distribution or concentration of transport sugars (i.e. stachyose, sucrose, verbascose) were observed. The data indicate that, in addition to being recycled intracellularly into Calvin cycle intermediates, amino acids produced during photorespiration may also serve as transport metabolites, allowing the mobilization of both carbon and nitrogen from the leaf under conditions of limited photosynthesis.