Effect of fertilization on photosynthetic characteristics of wheat flag leaf

Daily variations in net photosynthetic rate of wheat flag leaf under different N,P and K rates were observed by LI-6400.Four treatments-high N(300 kg·hm 2) and K(75 kg·hm 2) with low P(32.5 kg·hm 2)(N4P2K2),high K without N and P(N1P1K2),high P(65 kg·hm 2) without N and K(N1P3K1) and high N and P without K(N4P3K1) were used in the experiment.The results revealed differences among daily variations in net photosynthetic rate(Pn) of wheat flag leaf under different fertilization treatments.N4P2K2 treatment significantly promoted wheat flag leaf Pn.However,N4P3K1 treatment did not significantly promote wheat flag leaf Pn.Photosynthesis was generally weak in N1P1K2 and N1P3K1 treatments.Daily variations in flag leaf Pn under the same treatment but at grain filling,milky and mature stages were also compared.Difference in Pn among three main growth stages was highest under N1P3K1 treatment and lowest under N4P3K1 treatment,it was medium under N4P2K2 and N1P1K2 treatments.Pn was relatively high under N1P1K2 treatment at mature stage.This suggested that K fertilizer influenced daily variations in photo-synthetic characteristics of wheat flag leaf at mature stage.