CARBOHYDRATE-METABOLISM IN THE SILIQUA RELATING TO OIL-FILLING IN MUSTARD SEEDS

Developing siliquas on the mustard inflorescence were sampled at basal , middle and apical positions and the changes in free sugars and starc h in pod wall and seed vis-a-vis oil-filling in the seeds were studied . The dry matter and oil content per seed and pod wall was highest at initial stages in apical followed by mid-development stages in middle and late development stages in basal positions. The oil percentage in the pod wall decreased with the period of siliqua development. The pha se of rapid oil filling in the seeds varied from 20 to 40 DAF (days af ter flowering) in basal to 10 to 30 DAF in middle and 10 to 20 DAF in apical positions. The content of starch and total soluble sugars (% dr y weight basis) decreased in the seeds as well as pod walls but showed accumulation on per seed basis with a maximum at 20, 30 and 40 DAF wh ile on pod wall basis, the maxima of total soluble sugars was at 20, 2 0 and 40 DAF in apical, middle and basal position respectively. In the pool of total soluble sugars, the proportion of non-reducing sugars w as predominant. The activity of invertase (EC 3.2.1.26) declined while those of alpha-amylase (EC 3.2.1.1) and beta-amylase (EC 3.2.1.2) sho wed maximum values in the seeds as well as pod wall during the phase o f rapid oil-filling in the seeds. The results suggested that ontogeny and duration of seed development vis-a-vis the environmental condition s played an important role in lipid biosynthesis in mustard seeds.