STUDIES ON NITRATE REDUCTASE IN BRITISH ANGIOSPERMS II. VARIATIONS IN NITRATE REDUCTASE ACTIVITY IN NATURAL POPULATIONS.

In vivo nitrate reductase (NR) activity was measured in the leaves of plants from woodland, wooland-edge and open (ruderal) communities, Nitrate reductase activity was highest in the youngest fully-expanded leaves of all plants sampled. Nitrate reductase activity in populations from woodland and woodland-edge increased after feeding with nitrate; feeding with Mo had no significant effect. During the day NR activity in plants from each community increased to a maximum near the middle of the photoperiod and then decreased. These daily changes are discussed in terms of the possible regulatory roles of light and the transport of nitrate to the shoot. [ABSTRACT FROM AUTHOR]