叶绿体延迟荧光中730 nm成分产生机理的光谱学研究

叶绿体685 nm延迟荧光成分被认为源于PSⅡ作用中心的电荷复合。利用多种光谱学测量手段研究了叶绿体延迟荧光光谱中730 nm峰的产生机制。不同浓度下叶绿体延迟荧光光谱实验结果表明：初始随浓度的增加，延迟荧光光谱中685和730 nm成分强度均增强;当浓度增加到7.8 μg·mL-1时，685 nm成分强度达最大，730 nm成分强度继续上升;当浓度增加到31.2 μg·mL-1时，延迟荧光光谱中730 nm成分强度达最大，而685 nm成分已明显下降。吸收光谱实验结果表明：A₆₈₅/A₇₃₀在叶绿体浓度增加的过程中几乎不变。叶绿体730 nm荧光成分的激发光谱实验结果表明：685 nm光对730 nm荧光有较高的激发效率。上述实验结果表明叶绿体延迟荧光光谱中730 nm峰是由PSⅡ所发685 nm成分激发PSⅠ所产生的荧光。同一浓度下叶绿体延迟荧光光谱波形随延迟时间(1～9 s)的不变性进一步证明了这一结论。

Spectroscopic Research on the Mechanism for 730 nm Component in Delayed Fluorescence of Chloroplast

Charge recombination in reaction center of photosystem II (PS II) is regarded as the origination of delayed fluorescence (DF). The mechanism for 730 nm component appearing in the DF spectrum of chloroplast was studied with different spectral analysis methods. Experimental results of the delayed fluorescence spectrum at different chloroplast concentration showed that the apexes at 685 and 730 nm ascend when the concentration is relative low; the peak value at 685 nm reaches a maximum when the concentration is 7.8 microg x m(L-1), however, the apex at 730 nm is still increasing. The peak value at 730 nm finally reaches a maximum at chloroplast concentration of 31.2 microg x mL(-1), while the apex at 685 nm has apparently decreased. The results of absorption spectrum showed that the ratios of A685 to A730 are almost a constant during the process of increasing chloroplast concentration. Furthermore, the excitation spectrum for 730 nm fluorescence shows that the 685 nm light has a high excitation efficiency. Above experimental results indicated that the 730 nm component of DF spectrum is the fluorescence of chlorophyll a in PSI reaction center excited by 685 nm DF. Meanwhile, this conclusion was further verified by the invariability of DF spectrum at different delay time (1-9 s).