EFFECT OF TEMPORARY N STARVATION ON LEAF PHOTOSYNTHETIC RATE AND CHLOROPHYLL CONTENT OF MAIZE

Abstract

The photosynthetic rate (P) of maize (Zea mays L.) plants grown under growth room conditions was studied during and after a 10-day period of N starvation. The relationships between P and chlorophyll content, and P and nitrogen content were examined. Nitrogen deprivation, from the 18th to the 28th day, induced a decline of maximum photosynthetic rate, respiration and chlorophyll content; this effect was reversible. Recovery of photosynthetic capability occurred within 10 days of the resumption of nitrogen supply. Only partial recovery of chlorophyll content was recorded in the same time period. A low chlorophyll content and a relatively high photosynthetic rate were observed in N-deprived plants 4 days after the return to normal nutrient conditions. Chlorophyll efficiency was significantly greater in N-deficient than in control plants for approximately 1 wk, under light conditions close to saturation. Neither chlorophyll nor nitrogen content was correlated with maximum photosynthetic rate in N-starved plants. Under nitrogen deprivation, chlorphyll activity and leaf senescence (as measured by photosynthetic decline) appeared to be regulated independently.Key words: Nitrogen content, nitrogen deficiency, nitrogen stress, respiration, Zea mays L.