The effect of leaf water status on stomatal activity,transpiration and nitrate reductase of sweet potato

The diffusive resistance, transpiration, and nitrate reductase activity were examined in two field grown sweet potato (Convolvulus batatas L.) genotypes. A relationship between leaf water potential and activity of each measured physiological parameter was established.Slight increases in leaf diffusive resistance were observed as leaf water potential decreased, although complete closure of stomata due to water stress was not observed. No genotypic difference was ascertained in the relationship between leaf water potential and diffusive resistance. The stomatal response to humidity deficit is genotype-dependent, and gives a variation in water transport efficiency.The activity of leaf nitrate reductase was adversely affected by leaf water potential. Distinct genotypic differences were observed in the nitrate reductase activity. The data indicated that the stomata of field grown sweet potato are relatively insensitive to water stress, although the leaf nitrate reductase activity is influenced by it. Therefore, measurement of leaf diffusive resistance may not be a reliable estimate of plant water status and related physiological activity.