高温胁迫对水稻光合作用和叶绿素荧光特性的影响

目的]研究高温胁迫对植物光合作用和叶绿素荧光参数的影响。方法]以不同耐热性的2种水稻品种为材料,303、54、04、5℃温度下处理2 h后于25℃恢复3、6 d,分别在第03、6、天进行光合指标和叶绿素荧光的测定。结果]高温胁迫导致2种水稻的净光合速率（Pn）的下降。相同温度胁迫下,热敏感品种中优9801号光合速率下降的幅度大于Ⅱ优7号。Ⅱ优7号净光合速率的下降是可逆的,而中优9801号净光合的下降是不可逆的;在30～35℃高温下引起Ⅱ优7号Pn下降的主要因素为气孔因素;当温度达到40℃以上时,Ⅱ优7号Pn的下降主要依赖非气孔因素。非气孔因素是导致高温下中优9801号Pn下降的主要因素;在高温下能够迅速通过降低气孔导度和蒸腾速率从而减少水分丢失可能是Ⅱ优7号较中优9801号耐热的原因之一;高温引起热敏感品种中优9801号F0升高,Pn、Fv/Fm、qP、ETR显著下降,表明其PSⅡ反应中心遭到破坏或可逆失活,从而导致电子传递受阻,光化学效率降低,这是造成其光合速率下降的非气孔因素之一。结论]在同样的高温胁迫下,耐热品种Ⅱ优7号的荧光参数F0升高以及Pn、Fv/Fm、qP、ETR下降的幅度均明显小于中优9801号,并且在高温结束后6天可完全恢复到对照水平。PSⅡ较强的稳定性及自我修复能力是Ⅱ优7号耐热性较强的重要原因。

Effect of High Temperature Stress on Photosynthesis and Chlorophyll Fluorescence of Rice

Objective]The aim was to study photosynthesis and chlorophyll fluorescence parameters of plant under high temperature stress.Method]Two varieties of rice were treated at 30,35,40 and 45 ℃ for two hours,respectively,and then placed at 25 ℃ to resumed for 0,3,6 d,respectively.The photosynthesis and chlorophyll fluorescence parameters were measured.Result]High temperature resulted in the reduction of net photosynthesis in two kinds of rice,whereas the net photosynthesis in 'Zhongyou 9801' decreased more than 'Ⅱ you 7' under same high temperature.The decrease of the net photosynthesis in 'Ⅱ you 7' was reversible and that in 'Zhongyou 9801' was nonreversible.The decrease of net photosynthesis in 'Ⅱ you 7' was primarily due to stoma limiting factor at 30-35 ℃ whereas due to non-stoma limiting factor under 40 ℃.Non-stoma factor was the primary reason for the decrease of net photosynthesis in 'Zhongyou 9801'.Lower water loss resulted from rapid decrease of stomatal conductance and transpiration rate might be one of the reasons for thermotolerance of 'Ⅱyou 7'.High temperature resulted in significant increase of F0 and reduction of Pn,Fv/Fm,qP and ETR in 'Zhongyou 9801',which demonstrated that PSⅡ reaction center had been destroyed or inactivated reversibly and then induced electron transfer delay and photochemistry reduction.Conclusion] The increase of F0 and decrease of Pn,Fv/Fm,qP and ETR in 'Ⅱ you 7' were significantly weaker than in 'Zhongyou 9801'.Moreover,the above parameters resumed to control level after 6 d recovery.Higher stability and self-repair ability of PSⅡ were the important reason fors the thermotolerance of 'Ⅱ you 7'.