STUDIES ON NITRATE REDUCTASE IN BRITISH ANGIOSPERMS

Abstract

S ummary Leaf tissue from over 100 species, representing 40 families (mostly native British plants from natural populations), was assayed for in vivo nitrate reductase (NR) activity. From studies on the optimal assay conditions for the leaf tissue of 18 species, an assay procedure suitable for most species was devised. Higher levels of NR activity were measured in the leaves of ruderal species (mean NR activity = 4.39 ± 0.84 μmolh −1 g −1 fresh weight) than in woodland‐edge species (mean NR activity = 1.36 ± 0.29 μmolh −1 g −1 fresh weight). A survey of NR activity in the leaves of 41 woody species showed that most contained significant levels of NR activity (> 1.0μmol h −1 g −1 fresh weight) suggesting that nitrate assimilation was appreciable in these species.