| The effects and mechanism of He-Ne laser (5 mW-mm"2) irradiation on the variation of morphs and structure, physiological metabolic activities and the DMA repair capacity in damaged wheat seedlings induced by enhanced ultraviolet-B (10.08 kJ-m"2-d~1) radiation were studied. The pathway and mechanism of the DNA repair stimulated by He-Ne laser irradiation were indicated chiefly.1) Under the enhanced ultraviolet-B radiation, the wheat seedlings shown the decreased height and leaf area, accumulation of screening pigments and 'root-bending'. But following He-Ne laser irradiation, the height and number of the branch root were increased, and the 'root-bending' assay was mitigated. The activity of amylase and synthesis capacity of RNA and soluble protein were enhanced by He-Ne laser irradiation. This was the reason of increasing the wheat seedlings germination.2) After UV-B radiation the germination ability of the wheat was enhanced by He-Ne laser irradiation. Using t-test at P^O.05, there was significant difference between group of UV-B treated only and compound treatment group (with UV-B and He-Ne laser). The stimulation of the He-Ne laser irradiation effect on the vigor was clearer than the growth potential of germination and germination capacity. It indicated that the stimulation effect was expressed in early phase clearly.3) The results of studying on the chromosomal mutation and mitosis of the wheat irradiated by UV-B indicated that the rate of mitosis was inhabited by UV-B radiation (10.08 kJ ?m"2 ?d"1) in wheat cells, and some types of chromosome aberration were induced. Among of them, the fragments and lagging chromosomes were more than the correct, the rate of the fragments was 26.6%, lagging chromosomes was 32.8%. Under the condition of the enhanced ultraviolet-B radiation, the phenomenon of abnormal mitosis was first discovered, such as the three-bundle> four-bundle and six-bundle division of the chromosome when the cell is in anaphase. We think that the abnormal mitosis should be called 'multi-bundle division' or 'partition-bundle division' of the somatic chromosome. These 'bundles' of the chromosomes were distributed two polar, but the number of the 'bundle' is unequal possible between the two polar. In each 'bundle', the number of the chromosome is different from another 'bundle'. There are not the cell walls be formed between in two bundles, so it will be form the 'poly-bundle bodies'.4) The results of epicuticular observed with the scanning electronmicroscope (SEM, KYKY-2800, China) shows that the wax distribution could be changed by He-Ne laser irradiation.5) Changes in the concentration of malondialdehyde (MDA), glutathione (GSH), ascorbic acid (AsA), and activity of superoxide dismatase (SOD), catalase (CAT), peroxidase (POD), and UV-B absorbing compounds (absorbance at 300 nm) were measured to test the capacity of He-Ne laser irradiation on clearing the free radical induced UV-B radiation.The damage of wheat seedlings induced by enhanced UV-B radiation in physiology can be repaired partly by He-Ne laser irradiation with enzymatic and non-enzymatic system including of decreasing the MDA concentration, increasing the contents of AsA, GSH, UV-B absorbing compound, and the activities of SOD, CAT, POD.6) Using agarose gel electrophoresis and T4-endodeoxyribonuclease-V, which is a kind of restriction endonuclease of cyclobutyl pyrimidine dimer (CPD), the impacts of He-Ne laser (5 mW-mm"2) irradiation on DNA excision repair capacity in damaged wheat cells induced by enhanced ultraviolet-B (10.08 kJ-m~2-d~1) radiation were studied. The results indicated that the content of endonuclease sensitive sites (ESS) was reduced by He-Ne laser irradiation, which formed in cells irradiated by enhanced ultraviolet-B. With the irradiation of He-Ne laser, the excision of CPDs and the reduction of single strand breaks (SSB) contents which were the endonuclease sensitive sites (ESS) digested by T4-endodeoxyribonuclease-V had been stimulated in the wheat cells.7) By...
|
PDF Full Text Request