Translocation of Photosynthetic Products from Source Leaves to Aligned Juice Segments in Citrus Fruit

Translocation of 14 C-photosynthetic products from source leaves to fruit segments in direct vertical alignment to them was examined in ‘Hamlin’ sweet orange [ Citrus sinensis (L.) Osbeck] and ‘Marsh’ grapefruit ( Citrus paradisi Macf.). A single source leaf nearest (or next nearest) to a fruit was exposed for 1 hour to 14 CO 2 and then flushed with ambient air for 5 hours. Source, path, and sink tissues were separated and fruit was longitudinally quartered with respect to source-leaf attachment position. About 20% of the total 14 C-photosynthate was translocated into the fruit within 6 hours. The quarter aligned directly to the source leaf was allocated 77% and 85% of these assimilates in sweet oranges and grapefruit, respectively.