No abstract

carbon metabolism, sucrose metabolism, sucrose synthase, sucrose phosphate synthase, invertase, phosphoenol pyruvate carboxylase, malic enzyme, isocitrate dehydrogenase. AbstractActivities of some key enzymes of carbon metabolism sucrose synthase, acid and alkaline invertase, phosphoenol pyrnvate carboxylase, malic enzyme and isocitrate dehydrogenase were investigated in relation to the carbohydrate status in lentil pods. Sucrose remained the dominant soluble sugar in the pod wall and seed, with hexoses (glucose and fructose) present at significantly lower levels. Sucrose synthase is the predominant sucrolytic enzyme in the developing seeds of lentil (Lens culinaris L.). Acid invertase was associated with pod elongation and showed little activity in seeds. Sucrose breakdown was dominated by alkaline invertase during the development of podwall, while both the sucrose synthase and alkaline invertase were active in the branch of inflorescence. A substantial increase of sucrolytic enzymes was observed at the time of maximum seed filling stage (10-20 DAF) in lentil seed. The pattern of activity of sucrose synthase highly paralleled the phase of rapid seed filling and therefore, can be correlated with seed sink strength. It seems likely that the fruiting structures of lentil utilize phosphoenol pyruvate carboxylase for recapturing respired carbon dioxide. Higher activities of isocitrate dehydrogenase and malic enzyme in the seed at the time of rapid seed filling could be effectively linked to the deposition of protein reserves.

No abstract

Changes in the activities of sucrose synthase (SuSy), ADP-glucose pyrophosphorylase (AGPase), UDP-glucose pyrophosphorylase (UGPase), alkaline inorganic pyrophosphatase, 3-phosphoglycerate (3-PGA) phosphatase and amylases were monitored in relation to accumulation of starch in developing pods of mung bean (Vigna radiata L.). With the advancement in the seed development, the contents of starch rose with a concomitant fall in the branch of inflorescence and podwall after 10 d after flowering. The activity of UDPase in all the three pod tissues remained higher than the activity of AGPase showing it to be an important enzyme controlling carbon flux. The activity of alkaline inorganic pyrophosphatase in developing seed in contrast to 3-PGA phosphatase correlated with starch accumulation rate. Activity of β-amylase increased in all the pod tissues till maturity. It appears that the cooperative action of SuSy, UGPase and AGPase controls the efficient partitioning of sucrose into ADP glucose and thereby regulate the seed sink strength of the mung bean.Additional key words: alkaline inorganic pyrophosphatase, amylase, 3-PGA phosphatase, starch metabolism, sucrose synthase, Vigna radiata.

The activities of enzymes of pentose phosphate pathway (PPP) viz. glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and carbon metabolism viz. phosphoenol pyruvate carboxylase, NADP-isocitrate dehydrogenase and NADP-malic enzyme were measured in the plant and bacteroid fractions of mungbean (ureide exporter) and lentil (amide exporter) nodules along with the developing roots for comparison. The enzymes of pentose phosphate pathway in legume cytosol had higher activities at a stage of maximum nitrogenase activity and higher sucrose metabolism. However, bacteroids had only limited capacity for this pathway. The specific activities of these enzymes were greater in ureide than in anfide exporter. CO2 fixation via higher activity of phosphoenolpyruvate carboxylase in the plant part of the nodules in lentil might have been due to the greater synthesis of four carbon amino acids for amide export. The peak of NADP-isocitrate dehydrogenase in both legumes coincided with the pentose phosphate pathway enzymes at the time of high rates of sucrose metabolism and nitrogen fixation. Higher activities of NADP-malic enzyme were obtained in mungbean than in the lentil nodules. These findings are consistent with the role of these enzymes in providing reductant (NADPH) and substrates for energy yielding metabolism of bacteroids and carbon skeletons for ammonia assimilation.