LOCALIZATION OF NITRATE REDUCTION IN FERNS AND ITS RELATIONSHIP TO ENVIRONMENT AND PHYSIOLOGICAL CHARACTERISTICS

Summary The capacity for nitrate reduction was shown to be present in the roots and shoots of all fern species examined. In many species the root was the major site of nitrate reduction, irrespective of the availability of external nitrate. The capacity for root nitrate reduction was positively correlated with root glutamine synthetase activity. Some species exhibited multiple forms of glutamine synthetase in their shoots. The activity of chloroplastic glutamine synthetase appeared to be correlated with photorespiratory potential. Root nitrate assimilation was most pronounced in shade ferns.