Exploring the role of carbon and nitrogen metabolism in Chenopodium quinoa (Willd.) from the commencement of grain growth until maturity

Co-ordination between carbon and nitrogen metabolism maintain source-sink relationship between the reproductive (inflorescence and grain) structures. The metabolic changes that affect the quinoa grain development are un known. The present study evaluated carbon and nitrogen metabolism in quinoa genotypes IC411824, IC411825, EC507747 and EC507742 at different anthesis and post-anthesis stages, which affect grain growth and maturity. The increased activities of enzymes of carbon metabolism like acid invertase, sucrose synthase (cleavage), and sucrose phosphate synthase in inflorescence of quinoa genotypes from 75 to 90 days after sowing (DAS) may assimilate carbohydrates for grain development during post-anthesis. At 110 DAS, acid invertase and sucrose synthase (cleavage) activities were highest in grains, then reduced as grain development progressed and reached a minimum near grain maturity at 124 DAS. Nitrogen metabolizing enzymes like glutamate dehydrogenase and nitrite reductase reassimilate amides from the amino group of asparaginase at 90 DAS in inflorescence and at 124 DAS in maturing grains. IC411825 and EC507747 genotypes had better availability to assimilate the nutrients and their remobilization during the onset of grain development. Carbon and nitrogen metabolism enzymes at different stages of inflorescence and grain development influenced the source sink relationship, partitioning and accumulating assimilates during anthesis and post-anthesis in quinoa, leading to development of grains and establishment of yield. The identified source-sink dynamics in quinoa during grain development has the potential to be implicated in plant breeding strategies that aim to improve nutritional quality and yield.