番茄幼苗叶片光合作用、PSII电子传递及活性氧对短期高温胁迫的响应

Effects of Photosynthetic,PSII Electron Transport and Reactive Oxygen Species on Short-term High Temperature Stress in Tomato Seedlings

以番茄幼苗为试验材料,研究了光合气体交换参数、叶绿素荧光参数及PSII反应中心、PSII核心蛋白编码基因相对表达量和活性氧代谢对不同高温(25、30、35、40℃)胁迫12 h的响应,以期为番茄高温季节栽培提供参考依据。结果表明:随着温度的升高,番茄幼苗叶片光合碳同化能力受到抑制,30、35℃高温胁迫下番茄幼苗叶片光合作用减弱的原因主要为气孔因素,而40℃时则为气孔和非气孔因素共同限制。高温胁迫下番茄幼苗叶片PSII反应中心活性降低,PSII电子传递受阻,PsbA和PsbP基因相对表达量降低,即高温对番茄幼苗叶片的主要作用位点为PSII供体侧放氧复合体(OEC)和PSII受体侧Q_A向Q_B的传递过程,其原因主要与OEC功能的破坏及D1蛋白的降解有关。高温胁迫下PsbP基因相对表达量降低幅度大于PsbA,并且标准化OJIP曲线上0.3 ms处相对可变荧光(V_K)的增加幅度大于2 ms处相对可变荧光(V_J),说明高温胁迫对番茄幼苗PSII供体侧的伤害程度大于受体侧。番茄幼苗叶片在30、35℃高温胁迫12 h并没有诱导过量的活性氧(ROS)产生,这与非光化学淬灭(NPQ)有效淬灭过剩光能有关,而在40℃高温胁迫下番茄幼苗叶片NPQ显著降低,导致叶片中过剩光能(1-qP)/NPQ和ROS大量积累,这是导致光抑制加剧的重要原因。

In this study,the photosynthetic gas exchange parameters,chlorophyll fluorescence parameters,the gene relative expression of PSII core protein and the reactive oxygen species(ROS)metabolism in response to high temperature stress at different high temperature(25℃,30℃,35℃and 40℃)for 12 hours were studied.The results showed that photosynthetic carbon assimilation ability was inhibited with the increase of temperature in tomato seedlings.The inhibited reason for photosynthesis in tomato seedlings under 30℃and 35℃high temperature stress was stomatal factor,while stomatal and non-stomatal factors were limited collectively at 40℃.Under high temperature stress,the activity of PSII reaction center in tomato seedling leaves decreased,PSII electron transport was blocked,and the relative expression of PsbA and PsbP genes decreased,which implied that the main action site in response to high temperature was PSII donor side oxygen release complex(OEC)and the transmission process from Q_A to Q_B on the PSII receptor side in tomato seedling leaves.The relative expression of PsbP gene was significantly higher than that of PsbA under high temperature stress,and the relative variable fluorescence(V_K)at 0.3 ms on the standardized OJIP curve was greater than the relative variable fluorescence(V_J)at 2 ms,indicating that the of damage caused by high temperature stress on the donor side was greater than the receptor side on tomato seedlings.Tomato seedling leaves did not induce excessive production of reactive oxygen species(ROS)at high temperature stress of 30℃and 35℃for 12 hours,which was related to the non-photochemical quenching(NPQ)effective quenching of excess light energy,while NPQ was significantly reduced under 40℃stress,which resulted in excessive accumulation of excess light energy(1-qP)/NPQ and ROS in the leaves.This was an important reason caused further photoinhibition.