Nitrate uptake and the induction of nitrate reductase activity in wheat (Triticum aestivum L.) seedlings

Nitrate uptake and the subsequent induction of in vivo nitrate reductase activity in wheat were studied by investigating a euploid and certain ditelosomic stocks which exhibited in vivo activity significantly greater than that of the euploid. The kinetics of nitrate uptake were investigated, but the high activities of the ditelosomics were not caused by increased uptake of nitrate, although ditelo-7B^L exhibited unusual uptake dynamics. Analysis of the induction of nitrate reductase activity revealed a biphasic general pattern, with an initial rapid phase being followed by a slower but longer period of induction. The induction rate over the second period, although responsible for only a minor proportion of the total activity induced, was positively correlated with the final nitrate reductase level, unlike the rate over the first induction period. Several stocks exhibited high induction rates over one or other of the two phases, while ditelo- 1 A^s showed an abnormal monophasic induction pattern. At the end of the second period of induction, nitrate reductase activity became more or less steady, except for activity fluctuations associated with the time of application of induction stimuli.