Effects of nitrogen application on photosynthetic functions of flag leaves of superhigh-yield winter wheat at the flowering stage

In order to offer a technological support for fertilizer management of superhigh-yield winter wheat，effects of nitrogen application on the kinetics parameters of fluorescence of flag leaves of superhigh-yield winter wheat at the flowering stage under field condition were studied. ΦPSII(quantum yield of photosystem II photochemistry), qP(photochemical quenching), F’v/F’m (the efficiency of open reaction centers in light), NPQ (non-photochemical quenching), ETR(electron transport rate), net photosynthesis rate(Pn), intercellular CO2 concentration(Ci) and stomatal conductance(Gs) of the flag leaves were measured using Li-6400 Portable Photosynthesis System with an open flow gas exchange system. The results show that the kinetics parameters of fluorescence and the photosynthetic characteristics of the flag leaves at the flowering stage were regulated under the nitrogen application. As lighting prolonged, parameters of fluorescence of ΦPSII, qP, F’v/F’m, NPQ and ETR are gradually increased, and are stable at 21 minute or so. However, ΦPSII and qP under the high N level treatment is lower than that under the low N. F’v/F’m, NPQ and ETR are increased under the rational nitrogen application amount. Therefore, adaptability of the photosynthesis organs to the changes of environment is enhanced, and photosynthetic organs are protected. The highest grain yield is observed in the treatment with N 300 kg/ha application.