Partitioning of 13C-photosynthate in sweet pea (Lathyrus odoratus L.) plants during the flowering period

Photosynthetic rate and partitioning of photosynthate in sweet pea (Lathyrus odoratus L.) 'Early Lavender' whose leaves were administered C-13 during the flowering period were investigated. 1. The apical portion was a strong sink for C-13- photosynthates under 100% and 50% full sunlight. Partitioning of photosynthates to the apical portion increased significantly when the young flower buds were removed from the inflorescences on the first and second nodes above the inflorescences which had two open flowers. 2. The photosynthetic rate was the highest in the leaflet on the same node as the inflorescence which had two open flowers. The photosynthetic rate of the leaflet was decreased by removing the young flower buds of the inflorescence. The photosynthates from the treated leaves were translocated preferentially to the inflorescence on the same node. 3. The photosynthetic rate was kept high even in leaves on lower nodes. More photosynthates were partitioned to the apical portion of a shoot from lower leaves than those from the upper ones.