Effect of irrigation method and fertilization dose on photosynthetic physiology of super rice

To investigate the effect of irrigation and fertilization on photosynthetic physiology of super rice, a pot experiment was conducted using super rice "Zhongzheyou 1" as experimental crop. The study analyzed the photosynthetic physiology parameters net photosynthetic rate,P_n; intercellular CO2 concentration, Ci; photosynthetic light response curve and photosynthetic pigment contents of chlorophyll a (Chl a), chlorophyll b (Chl b), carotenoid (Car), total chlorophyll content (TCC) of rice under three irrigation methods controlled irrigation (CIR), intermittent irrigation (IIR) and flood irrigation (FIR) and three fertilization levels non-fertilization (F₀), low fertilization (F_L) and high fertilization (F_H). It also conducted correlation analysis for P_n and chlorophyll contents. The results showed that compared with FIR, CIR and IIR treatments (saving-water irrigation methods) significantly increased P_n. It, however, failed to significantly enhance C_i at the jointing, heading and milking stages. Both CIR and IIR increased light saturation point (LSP) by 9.2%~36.8% at the jointing and heading stages and apparent quantum yield by 6.7%~31.5% respectively at the three growth stages, while they decreased light compensation point by 3.2%~12.8% at the jointing, heading and milking stages. Compared with FIR, CIR respectively increased the contents of Chl a, Chl b, Car and TCC by 19.1%~76.3%, 44.5%~98.5%, 31.5%~117.4% and 45.4%~145.0% at the jointing, heading and milking stages. IIR treatment respectively enhanced the contents of Car and TCC by 4.2%~45.8% and 31.5%~117.4% at the three growth stages. Under the three irrigation treatments, photosynthetic indices and photosynthetic pigment contents were higher under fertilization than non-fertilization treatments. High fertilization also resulted in higher photosynthetic indices and photosynthetic pigment content than low fertilization. Correlation analysis showed significant correlation between P_n and photosynthetic pigments contents, which correlations were influenced by growth stages. CIR and IIR improved photosynthetic capacity under strong light, and adaptability to weak light; and significantly increased light utilization rate. Compared with FIR, CIR and IIR increased photosynthetic pigment content but delayed photosynthetic pigment degradation. It was concluded that CIR and IIR treatments enhanced photosynthetic capacity, improved the photosynthetic light response curve and increased photosynthetic pigment contents. In terms of fertilization rate, high fertilization increased photosynthetic capacity of "Zhongzheyou 1" under saving-water irrigation treatments.