Photosynthetic Oxygen Production Facilitates Translocation of11C-Labelled Photoassimilates from Tendrils and Leaflets ofPisum sativumL

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Abstract
The translocation profiles of 11C-photoassimilates from either tendrils or leaflets of the compound leaf of Pisum sativum were similar in shape, speed and susceptibility to blockage by chilling and heat girdling. When the feed leaf component was exposed to an anaerobic gas stream consisting of N2 gas supplemented with 40 Pa CO2, the export of previously-fixed 11C-photoassimilates from both leaflets and tendrils continued in the light, but stopped in the dark. However, in the light, translocation of 11C-assimilates from the leaflet was rapidly blocked by a flow of pure N2 (i.e. anoxia). Movement of 11C-assimilates from the leaf of another C3 plant, sunflower, was similar to that from the pea leaflet. In contrast to both laminar leaf components, export from the tendrils was stopped under pure N2 only in the dark. Taken together the data suggest that photosynthetic O2 production facilitated the movement of 11C-assimilates in the absence of exogenous O2. The differences observed between the tendrils and the leaflets exposed to pure N2 could be attributed to the greater capacity of tendrils to produce and recycle CO2 to support photosynthetic O2 production in the light.

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