Fructose 2,6-bisphosphate-modulated photosynthesis in Sorghum leaves grown under low water regimes

Abstract

The influence of low water potentials on photosynthetic sucrose formation, fructose 2,6-bisphosphate (F2,6BP) content, partitioning of photosynthate and related enzymes was investigated in control and water- stressed leaves of Sorghum bicolor cv. CSH 5. The accumulation of F2,6BP in water-stressed plants reduced sucrose formation in the leaves. The activities of fructose 1,6-bisphosphatase and sucrose phosphate synthase were reduced in water-stressed plants. The distribution of 14C into starch increased with increasing stress, while the incorporation into sucrose was drastically reduced in the stressed plants. The activity of fructose 6-phosphate 2- kinase was very high in stressed plants, while the levels of fructose 2,6- bisphosphatase were low. The results suggest that low water potentials result in F2,6BP accumulation, which modulates sucrose synthesis and carbon- partitioning in sorghum leaves.