Distribution of nitrate assimilation between the root and shoot of legumes and a comparison with wheat

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Abstract
Legumes of the Phaseoleae (Glycine maxL. Merr.,Phaseolus coccineusL.,P. vulgarisL.,Vigna radiataL. Wilczek andV. unguiculataL. Walp.), when grown on 10 mMnitrate, had a low in vitro nitrate reductase (NR) activity in the root compared to the shoot (Cicer aerietinumL.,Pisum sativumL. andVicia fabaL.), Genisteae (Lupinus albusL.) and Trifolieae (Medicago sativaL. andM. truncatulaGaertn.), 30–60% of their total NR activity was in the root. The Phaseoleae had a higher nitrate content in the shoot. Decreasing the nitrate supply increased the relative proportion of NR activity in the root of garden pea (Pisum sativum) and wheat but did not alter the predominantly leaf‐based assimilation of nitrate inPhaseolus vulgaris.When in vitro NR activity of the pea shoot was compared with the in vivo NR activity and the rate of accumulation of reduced N by this tissue, similar values were obtained. In vitro NR activity of the wheat shoot was 5 times its in vivo NR activity and 12 times its rate of accumulation of reduced N.