Growth and physiological response of tomato plants to different periods of nitrogen starvation and recovery.

摘要

Young, vegetative-state tomato plants, starved of N for 1, 3 or 7 d, followed, in each case, by a 7-d recovery period with nutrient solution containing N, were examined. Relative growth rate (RGR), leaf photosynthesis and leaf expansion were reduced after only 1 d of N starvation. Tissue N concentrations fell during N starvation, the effect being stronger in stems and leaves than in roots, while the growth rate of roots, expressed as a fraction of total plant mass, was less affected than for stems or leaves. Net assimilation rate (NAR) was affected more than leaf area ratio (LAR) in the early stages of N-starvation. During the N starvation period, NO3-N concentrations in plant organs fell quickly and were negligible after 7 d. During the recovery period, the RGR and plant total-N concentration of starved plants were restored to control values. The critical N concentration for optimum growth rate was found to be 3.8%, which was reached before 3 d of N starvation.