Verbreitung und Funktion der Nitratreduktase in Leguminosenfrüchten

Abstract

In pericarps, testae and cotyledons of developing fruits of different legumes belonging to the tribes Phaseoleae and Vicieae , respectively, nitrate reductase has been investigated with respect to diurnal and developmental changes in the enzyme activity. Species belonging to the Phaseoleae exhibited nitrate reductase activity in the pericarp tissue only, whereas species of the Vicieae showed nitrate reductase activity in pericarp, testa, and cotyledons during embryogenesis. The nitrate reduction capacitiy of the different fruit organs has been calculated by integration of the nitrate reductase activity during the whole peroid of embryogenesis taking into account the existence of different zones of enzyme activity in the pericarps, and the diurnal and developmental changes, respectively. Evidently nitrate reduction in the fruit accounts for less than 10 % of the nitrogen accumulated in the ripe seeds of the same legume fruit, but nitrate reduction of the pericarps increases by a high percentage, if the developing fruits are exposed to translocation shortage of organic carbon and nitrogen compounds into the seeds. The consequences of these findings are discussed with respect to the physiological function of the pod in relation to seed development.