Research Of Ultra-weak Luminescence Of Leaves During Senescence

Many investigations of senescence have been done by scientists from the aspects of physiological or biochemical parameters, but the senescence mechanism at present is not clear. In order to describe the process and mechanism of senescence, the characteristic of ultra-weak luminescence during leaf senescence in natural or stress conditions was determined with luminescence technique. The results show that: (l).In the process of natural senescence, the ultra-weak luminescence and biochemical parameters (superoxide dismutase SOD, lipoxygen-ase LOX, chlorophyll) of Nematanthua Cheerio leaves have obvious changes with the leaf position increasing (the leaf age increasing). The spontaneous luminescence intensities firstly increase and then decrease, the relaxation of DL (delayed luminescence) firstly slows and then quickens, and the mature leaf has the strongest spontaneous luminescence and the slowest DL. In the mean, the SOD activity and the content of chlorophyll roughly decrease, and the LOX activity has a little rise after a markedly fall. Though the change curves are different, there is a close relationship between ultra-weak luminescence and these biochemical parameters. (2) In the process of senescence on temperature stress, the maximal intensity and relaxation of DL have obvious changes. Whether the treated temperature is higher or slower than environment temperature, the maximal intensity will reduce and the relaxation of DL will quicken. With the treated time increasing, the relaxation of DL will quicken, too. The changes of the SOD and LOX activity are respective different with DL, but it is closely related to the DL. (3) In the process of senescence on perhydrol (H₂O₂) stress, all concentrations of experiment can make the relaxation of DL quickening, while different concentrations of H₂O₂ can bring different changes of relaxation of the DL.The regular change of ultra-weak luminescence during senescence under different conditions indicates that ultra-weak luminescence may be regarded as a systematic parameter to research the senescence process from the interaction change of each portion in living system. So this method can be as a new way of biophysics to probe the senescence mechanism.