Effects of high temperature on characteristics of photosynthesis and chlorophyll fluorescence and yield components of rice at heading stage

【Objective】In order to investigate the effects of hightemperature on photosynthetic characteristics, chlorophyll fluorescence characteristicsand yield components of rice at heading stage, and to provide theoretical basis for reducing high temperature damage to rice during rice growth and development.【Method】The effects of different temperature treatment 35℃/30℃(daytime/evening) (T0, ordinary temperature) and 40℃/35℃(daytime/evening) (T5, high temperature) at heading stage on photosynthetic characteristics, chlorophyll fluorescence characteristics and yield components of rice cultivars Yanliangyou 1618(Y1618) and Nei 5 you 8015(N8015) were studied by using artificial climate chamber.【Result】Compared with T0 treatment, net photosynthetic rate(P_n) and intercellular CO₂ concentration(C_i) of Y1618 decreased significantly by 31.05% and 54.26%, respectively and C_i of N8015 was significantly reduced by 62.61% under T5 treatment, the transpiration rate was significantly increased by 104.55%(P< 0.05, the same below).Other photosynthetic parameters did not change significantly(P> 0.05, the same below).After high temperature treatment, P_n of N8015 was significantly higher than that of Y1618.The high temperature treatment reduced the fluorescence intensity of each phase of Y1618 and N8015, delayed the arrival time of chlorophyll fluorescence to P peak of the both cultivars, and reduced photochemical efficiency, specific activity and performance index.The high temperature treatment also decreased significantly grains number and weight, with lower degree of decrease for N8015.【Conclusion】To some extent, the high temperature at heading stage can significantly inhibit the photosynthetic parameters of rice, decrease the fluorescence intensity of each phase of rice, inhibit the photochemical efficiency and reduce panicle weight, solid grain number and grain weight of rice.The overall performance indexes of N8015 are higher than Y1618, indicating that N8015 is more resistant to high temperature than Y1618.