[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).