Effects of water and nitrogen treatment on endogenous hormone abscisic acid and photosynthetic characteristics of foxtail millet
In order to explore the effects of nitrogen fertilizer and drought treatment on the physiological characteristics of foxtail millet,the effects of different water and nitrogen treatments on endogenous hormone abscisic acid(ABA),chlorophyll content,photosynthetic characteristics and water and nitrogen use efficiency of foxtail millet were studied by pot culture with"Jigu 22"as material.Three water treatments were set up:normal water(CK,60%-70%of field water capacity),drought at seedling stage(W1,30%-40%of field water capacity),drought at booting stage(W2,30%-40%of field water capacity)and two nitrogen treatments were conducted:N 150 kg/hm2(N150)and no nitrogen(N0).A rainproof shelter was used to protect the pots against rain during growth.The results showed that ABA content in leaves was increased under water stress,and increased greatly under nitrogen application.ABA content in roots was also increased,but the increase was more without nitrogen application.The photosynthetic response curves of different treatments at flowering stage were significantly different,and the treatment of drought at seedling stage and nitrogen application had obvious advantages.There were great differences in the fluorescence properties of leaves in flowering stage.Under water and nitrogen stress,the potential maximum photochemical efficiency of photosystem II,the quantum yield of photons absorbed by the reaction center for electron transfer decreased,the quantum ratio of photons absorbed by the reaction center for heat dissipation increased,and the performance index based on light energy absorption decreased sharply.The relative variable fluorescence intensity content of j point in the dry nitrogen treatment at booting stage was significantly higher than that in the control.The performance index based on light energy absorption was the lowest in the dry nitrogen treatment at booting stage,and the energy captured by unit reaction center for electron transport was the highest.After heading of foxtail millet with different water and nitrogen treatments,the SPAD value was decreased with time,and the nitrogen application treatment significantly increased the SPAD value of leaves.The water use efficiency of drought at seedling stage and nitrogen application treatment was the highest,and the nitrogen use efficiency of no nitrogen application treatment was significantly higher than that of other treatments.Under the same water treatment,the water use efficiency of nitrogen application treatment was significantly higher than that of no nitrogen application treatment,while the nitrogen use efficiency showed the opposite trend.Drought treatment at seedling stage with nitrogen application significantly improved photosynthesis by increasing SPAD value of leaves and net photosynthetic rate at flowering stage,and significantly increased water and nitrogen utilization rate,so as to ensure relatively stable yield of foxtail millet.
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