ACTIVITY OF NITRATE REDUCTASE AND ACID-PHOSPHATASE IN LEAVES OF WHEAT, AFTER A PERIOD OF CESSATION OF WATERING

The water potential (PSI-W), the activity of in vivo nitrate reductase (NRA) and the total activity of acid phosphatase (APA), were determined in leaves of three varieties of wheat (T. aestivum), at the end of a period of cessation of watering (CW) and 24 hours after watering resumption. The assays were sensitive to cessation of watering. As psi-w lowered, NRA decreased rapidly whereas APA increased significantly. When irrigation resumed, the opposite variation was observed. Thus the assays were sensitive to variation of psi-W. The variability of the assays used to measure the activities was too high however to allow consistent differences among varieties to be shown. An increased variability was observed after rewatering especially in the case of NRA.