[Objective] Effect of tillering stage shading on photosynthetic characteristics of rice leaves was studied.[Method] Two cultivated rice,Shennong265 and Shennong9816,were shaded with 50 ％ interception of photosynthetically active photon flux density during the tillering stage for 15 days in a pot experiment.The chlorophyll content(SPAD value),gas exchange and chlorophyll fluorescence parameters were measured in the stage of shading and re-illuminated.[Result]The SPAD value,internal CO2 concentration(Ci),stomatal conductance (Gs),actual photochemical efficiency(ΦPS Ⅱ),photochemical efficiency of PSⅡ the light(Fv/Fm) and photochemical quenching(qP) in leaves of Shennong265 and Shennong9816 increased significantly under shading,but net photosynthetic rate(Pn),electron transport rate (ETR) and non-photochemical Quenching (qN) decreased significantly in leaves.The Pn and Fv/Fm of Shennong265 leaves and the E,Gs and qN of Shennong265 and Shennong9816 were significantly higher than those of the control at 5 days after light recovery.There were no significant difference in gas exchange and fluorescence parameters of Shennong265 and Shennong9816 between the shading treatment and the control at 10 days after light recovery.[Conclusion] These results indicate that Shennoag265 and Shennong9816 are not affected by irreversible damage under 50 ％ shading treatment and two rice varieties increase the utilization efficiency of light energy to adapt to the low light environment by increasing the chlorophyll content and opening degree of PS Ⅱ reaction center.%[目的]研究分裂期遮光对水稻叶片光合特征的影响.[方法]采用盆栽实验,选用沈农9816和沈农265水稻品种为试验材料,在50％的遮光处理下遮光15 d,研究分蘖期水稻在遮光和复光过程中叶片叶绿素含量、气体交换参数和荧光参数的变化规律.[结果]50％遮光处理使沈农9816和沈农265叶片的叶绿素含量(SPAD值)、胞间二氧化碳浓度(Ci)、气孔导度(Gs)、实际光化学效率(ΦPSⅡ)、光系统Ⅱ最大光化学效率(Fv/Fm)和光化学猝灭(qP)显著增加,使叶片的净光合速率(Pn)、电子传递速率(ETR)和非光化学猝灭(qN)显著降低.恢复光照的第5天沈农265叶片的Pn和Fv／Fm显著高于对照,沈农265和沈农9816叶片的E、Gs和qN也显著升高.复光第10天时,两参试水稻叶片的气体交换和荧光参数与对照无显著差异.[结论]50％遮光处理未对沈农265和沈农9816构成不可恢复的伤害,参试水稻通过增加叶绿素含量和PSⅡ反应中心的开放程度,提高光能利用效率以适应弱光环境.
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