闪光频率对番茄叶片光合系统动态响应的影响

Dynamic Responses of Photosynthetic Apparatus in Tomato Leaf to The Pulsed Light Frequency

在红光LED频闪光照射下,采用光合测定系统(CIRAS-2)和光纤光谱仪(QE65),同步测定了闪光频率下番茄叶片的净光合速率Pn、气孔导度Gs、胞间二氧化碳浓度Ci和叶绿素荧光信号F的动态响应。随着闪光频率从0.01 Hz向10.00 Hz增加,Pn振荡幅度减小,至0.25 Hz以上时Pn振荡幅度不显著;光合光能转化效率LCE'逐渐上升至0.25 Hz以上时达最大;与光系统Ⅱ光化学活性的初级醌受体暗期再氧化程度或光期再还原程度有关的光脉冲荧光相对变化量Fpcr也从较高水平迅速下降,至0.12 Hz时达最低值,之后较快回升,至0.50 Hz以上趋稳并接近于中等水平,显示出ATP池和NADPH池的较强缓冲能力。频闪光的光期Gs始终维持在较高水平,对外界CO2进入胞间的Ci无显著影响。而频闪光的光→暗期间的光后光合碳吸收衰减或暗→光期间的暗后光合碳吸收再启动过程的相对同化负荷变化量ΔACr在0.10 Hz以上衰减趋0,暗示着核酮糖-1,5-二磷酸(ribulose-1,5-bisphosphate,RuBP)的消耗与再生趋于平衡状态,呈现出较强的RuBP池的缓冲能力。综合分析表明,频闪光下,ATP池、NADPH池和RuBP池呈现出的联合缓冲能力,对光后暗期或暗后光期RuBP的持续再生或再生恢复均有维持效应,从而增加闪光频率即相应缩短暗期和光期,致使光合碳吸收Pn的暗期下降幅度减小和光期上升幅度减少,呈现Pn振荡幅度减小至趋稳的现象。

With illumination of tomato leaf by different pulsed light frequencies from light-emitting diodes, the dynamic processes of net photosynthetic rate （P,）, stomatal conductance （G,）, intercellular CO2 concentration （C,） and chlorophyll fluorescence （F） were simultaneously measured by using portable photosynthesis system （CIRAS-2, PP System, UK） and fiber-probe fluorescence detection system （QE65000, Spectrometer Ocean Optics, Inc. USA）. The insignificant effect of pulsed light frequencies on Gs value was observed, which didn＇t prevent CO2 diffusion from leaf chamber into tomato mesophyll cell. However, the pulsed light frequency distinctly affected P, charactered with oscillation. The oscillation range gradually reduced to minimal value （0） accompanied with corresponding increase of light conversion efficiency （LCE＇） to maximal value （0.36） when pulsed light frequencies varied from 0.01 Hz to 10.00 Hz. Furthermore, relative variable quantity of chlorophyll fluorescence （Fpcr）, which related to level of primary quinone acceptor of photosystem 11 reoxidation in duration of pulse times and reduction in subsequent dark times, rapidly decreased from 0.79 at 0.01 Hz to 0.11 at 0.12 Hz and then increased to stable value（0.36 to 0.39 between 0.50 Hz and 10.00 Hz）. It showed that buffering capacity of ATP pool and NADPH pool was controlled by electrons released from PS Ⅱ. The relative variable quantity of assimilatory charge （△ACr）, which was calculated from oscillation curve of photosynthesis during a period of pulsed light illumination, had almost reduced to 0 value when pulsed light frequencies varied from 0.10 Hz to 10.00 Hz. It demonstrated that higher buffering capacity of ribulose-1, 5-bisphosphate （RuBP） pool should play an important role in holding equilibrium state of consumption and regeneration of RuBP. Consequently, the synergistic effect of ATP pool, NADPH pool and RuBP pool can perfectly maintain RuBP regeneration and accumulation during pulsed light illumination. In other word, greater frequency of pulsed light can prevent oscillation photosynthesis occurrence.