Photosynthesis and Assimilate Partitioning in Mungbean in Response to Source-Sink Alteration

The effect of alteration in source-sink ratio by deflowering and defoliation technique on photosynthesis rate was examined in mungbean ( Vigna radiata L.] Wilczek) var. PS 16. Deflowered plants where sink demand was decreased, maintained a higher rate of photosynthesis in spite of their higher starch content in the leaves. This treatment also increased the partitioning of assimilates to leaves, stem, roots and nodules indicating the existence of alternative sink capacity. The higher rate of photosynthesis of deflowered plants was associated initially with lower stomatal diffusive resistance and subsequently with higher leaf nitrogen content. Increase in sink demand for a particular leaf by excising other source leaves also increased the rate of photosynthesis. These results are discussed in relation to possible regulation through hormones.