Changes in nitrogen contents and in proteolytic activities in different parts of field-grown wheat ears (Triticum aestivum L.) during maturation

Aminopeptidase, carboxypeptidase and neutral endopeptidase activities were analyzed in glumes and in kernels of field-grown wheat (Triticum aestivum L.) during ear development. Kernels harvested on two dates were subdivided into outer pericarp, cross cells, endosperm and embryo. In developing parts with a net nitrogen influx (young glumes, embryo, endosperm) the aminopeptidase activity is high, but in nitrogen-mobilizing tissues (senescing glumes, Outer pericarp) this activity decreases. Carboxypeptidase is most active in fully expanded tissues. Neutral endopeptidase shows the highest activity in the nitrogen mobilizing parts and extremely low activity in the embryo and the endosperm.