Source-sink Relationship for Translocation and Distribution of C-14 Carbohydrates in Pumpkin

Abstract

The pattern of photoassimilate transfer and allocation from leaves to other organs of confectionery seed pumpkin (Cucurbita pepo L.) was investigated in a greenhouse environment. Fully-developed leaves located at different nodes on the vine were labeled with (CO2)-C-14, and subsequent transfer of (14)4C, carbohydrates into fruit, leaf, stem, and root was measured. The (CO2)-C-14 fixation and the amount of C-14-labeled photosynthetic translocation into sink varied by leaf position, and the leaf born, at the center between the first and second fruit-bearing nodes served as the strongest source. While the proportion of C-14 transferred from a leaf to other parts was similar, closer distance between the source and the sink tissues meant greater amount of translocated C-14. The first fruit served as the strongest sink for C-14 translocation, followed by stem, leaf, the second fruit, and root tissues.