Abstract: 【Objective】The effect of different light qualities on photosynthesis and photosystem of maize leaves was studied to explore the physiological mechanism of photosynthesis in cloudy.【Method】Two maize varieties were chosen as materials. Zhengdan 958 (ZD958) is a common variety mainly planted in northern China, and Xianyu 335 (XY335) is sweeping in the Northeast of China. The two varieties were planted in field at National Maize Technology Innovation Center of the Huanghuaihai Region. Four light quality treatments were designed, including red film (R), green film (G), blue film (B) and white gauze simulation on cloudy days as a control (CK) at the stage of V6. After 10 days of treatment, the parameters of gas exchange, chlorophyll a fluorescence transient and light absorbance at 820 nm of maize leaves were measured for analyzing the effects of different light qualities on photosynthesis and photosystem.【Result】The percentum of radiant energy of different light wave bands in overall radiant energy was the same with sunny days in cloudy days and simulated-cloudy days, but its absolute amount were significantly declined and the reduction of blue-violet was the largest. Blue film's decline was minimum at 300-510 nm in the three films. On the other hand, the percentum of radiant energy of blue film at 300-510 nm increased significantly than sunny days. The results showed that leaves net photosynthetic rate (P_n) of XY335 and ZD958 decreased significantly under green film, red film and blue film, and the decrease was 40.13%, 32.68%, 22.00% and 46.92%, 37.69%, 27.46%, respectively. Compared with the control, the stomatal conductance (G_s) was decreased significantly, but intercellular CO₂ concentration (C_i) was increased significantly, which demonstrated that the declines of P_n were not mainly related to stomatic factors under different light qualities. The probability of that a trapped exciton the moves an electron further than Q_A by trapped exciton (Ψ_o) and performance index (PI_ABS) of maize leaves were all declined significantly besides XY 335 under blue film, showing G＞R＞B. This demonstrated that the performance of PSⅡ was restrained significantly, especially the performance of the electron transport chain after PSⅡ reaction center electron acceptor side. The performances of electron donor side and acceptor side of PSⅡ were all declined significantly besides XY 335 under blue film. This demonstrated that there is a little effect of blue film on electron donor and acceptor. However, the decrease of activity of electron donor side was larger than the electron acceptor side under green film, but it was opposite under red film. It was found that the performance of PSⅡ (Ψ_o) was declined under different light qualities besides XY 335 under blue film. Most importantly,the performances of PSⅠ(ΔI/I_o) and Φ_{（PSⅠ/ PSⅡ）}of two varieties were all declined under different films, showing R＞G＞B.【Conclusion】The decline of blue-violet of visible light made the performance of PSⅠ dropped significantly in cloudy days, which resulted in the depressed coordination between PSⅡ and PSⅠ. And then the performance of electron transport chain in photosynthesis declined, and caused P_n decline.

Key words: maize, light quality, photosynthesis, photosystem, chlorophyll fluorescence