Accumulation of starch, protein and activities of sucrose-cleaving, transaminating enzymes in chickpea pods raised through liquid culture

Using liquid culturing of detached inflorescences of chickpea (Cicer arietinum), manipulations with respect to sugars and amino nitrogen were done on the feeding sap entering the developing pods. The effects of such manipulations on the accumulation of biomass in seed, starch and protein in cotyledons and the activities of soluble acid and neutral invertase (EC 3.2.1.26), sucrose synthase (cleavage, EC 2.4.1.13), glutamate oxaloacetate transaminase (EC 2.6.1.1) and glutamate pyruvate transaminase (EC 2.6.1.2) in pod tissues were investigated. Compared with supplied hexoses, addition of sucrose in the culture medium resulted in higher accumulation of biomass in seed and decapitation of detached inflorescence did not affect this biomass accumulation. Appearance in seed tissues of over 70 % of 14C in extracted sugars for sucrose alone indicated entry into seed of translocated sucrose as such and/or its reconstitution in these tissues. Comparative effect of exogenously-fed cold sugars on incorporation of 14C from sucrose into EtOH-soluble products of seed tissues indicated that a minimum level of sucrose in transport stream is essential for an effective unloading of this sugar into seeds. Whereas in pod wall and seed coat, the cleavage of sucrose is principally catalysed by soluble neutral invertase, in cotyledons both soluble neutral invertase and sucrose synthase (cleavage) are involved. The accumulation of proteins in cotyledons was significantly higher with amides, compared with inorganic nitrogen, added to the culture medium. In pod wall and seed tissues, the activity of glutamate oxaloacetate transaminase was much higher than that of glutamate pyruvate transaminase. Increased supply of glutamine at an adequate fixed level of sucrose resulted in diversion of sucrose from starch to protein synthesis with concurrent increase in the activities of both transaminases in cotyledons.