FORMATION OF PROTEINS AND AMINO-ACIDS IN WHEAT DURING GRAIN DEVELOPMENT

In two previous papers published in this journal, results concerning t he impact of delayed harvest and late nitrogen top-dressing on certain quantity and quality characteristics of ripe grain were reported. The present paper gives an account of the process of grain formation in t wo Hungarian wheat varieties (MVM, Mv21), which were studied during th e ripening period (from the 6(th) day after anthesis until full grain maturity). Eight sampels were harvested at different stages of maturit y in four experimental years. To investigate the influence of nitrogen quantity on wheat proteins two different doses were applied. The chan ges in nitrogenous compounds giving a positive ninhydrin reaction in t he stems, leaves and grains were also studied in the period after anth esis, as where the quantity and quality of different molecular weight proteins and amino acids. The ninhydrin positive substances decreased during the period of grain development in the stems, leaves and grains , This trend was observed mainly in the case of grains, due to gluten protein formation. The proteins were separated by HPLC. The migration of proteins between the plant tissues and in high molecular weight pro teins the increase in the grain yield were monitored. The formation of free amino acids showed characteristic trends during the period of se ed development. The changes in ornithine content observed during grain development could merit particular attention. There was a high ornith ine concentration after flowering in both the wheat varieties studied. Later, a rapid decrease in the ornithin concentration could be detect ed, possibly due to the role of ornithine in amino acid biosynthesis t hrough the absorption and transport of NH3.