Nitrogenous compounds and protease activity in developing testapericarp and endosperm of high and low protein wheat (Triticum aestivum L.)

Abstract

Nitrogenous compounds such as total protein, true protein, soluble protein, non-protein nitrogen, total amides, ammonium, nitrate, nitrite, free amino acids and neutral and acid protease activities were estimated in a high protein wheat cv Shera (12.8% protein) and a relatively low protein wheat cv C-306 (10.4% protein) at different stages of grain development. All the nitrogenous compounds studied, as well as protease activities, were located in both testa-pericarp and endosperm. Developmental patterns and relative levels were, more or less, similar when expressed on per organ basis, or on dry weight basis. In the testa-pericarp; dry weight, total protein, soluble protein, true protein, amide, ammonium, nitrate and nitrite contents increased during development, and were higher in Shera, compared with cv C-306. Non-protein nitrogen content decreased during pericarp development, and was higher in cv Shera, compared with cv C-306. Free amino acid content and protease activities decreased in developing pericarp, and were lower in cv Shera, compared with cv C-306. Similar developmental patterns and relative levels of nitrogenous compounds and protease activities were found in endosperm. It is suggested that both testa-pericarp and endosperm make qualitatively similar contributions to the accumulation of nitrogenous compounds in developing wheat grain; higher protease activity in the endosperm of C-306 is not responsible for lower protein accumulation, and nitrate and nitrite are assimilated mainly in the green pericarp of the wheat grain. It appears that differences in protein contents of Shera and C-306 wheat arise primarily from differences in translocation of nitrogenous solutes from the phloem sap to the peduncle and pericarp, enroute endosperm.