Study Of Signal Transduction Mechanisms And Physiological And Biochemical Response Of Zea Mays L. Induced By UV-B Radiation

Ozone depletion in stratos phere has led to the increase of solar UV-B radiation reaching to the earth surface, which would damage biosphere to various degrees. Compare to 1980, ozone decrease 6% every 10 years in southern hemisphere middle latitude area between 1997 to 2002.UV-B radiation affects all of the esosystem,which has been shown increased trend from now on.There were some studies showed that plants suffer more UV-B stress than animals because its can not move. Then the damage of plants lead to change of ecosystem structure, function and stability.And this effect bring enormous disaster.Thus, reaserching of UV-B is very meaningful.Calcium as a second messenger in cell signal transduction system,which has mediated regulation of various physiological and biochemical response of plants. The Ca²⁺ in the physiological function of plants has been an active research area in domestic and abroad.At present, domestic and foreign-related research focused largely on apparent physiological indices after the plants treated with alleviate UV-B radiation effector or use UV-B radition and different conceration Ca²⁺ solutions.There are rare reports in the internal mechanism.The major avenues of approach main corridor of Ca²⁺ signal transduction system and the regulation mechanism of this corridor under UV-B stress has not been determined.In this paper,we simulate natural condition UV-B radiation,while use different doses of calcium intracellular IP3 channel blocker heparin (Hprain), activity of intracellular CaM inhibitor trifluoperazine (TFP), plasma membrane calcium channel blocker lanthanum chloride (LaCl₃)treat the plant, then use the methed of Confocal Laser Scanning Microscopy Technology and the combination of fluorescent indicator to explore the concentration of intracellular Ca²⁺ transient change in trend of UV-B induced plant leaves, investigate the major avenues of approach main corridor of the process of plant cell calcium signal transduction on the induce of UV-B radiation. Then we investigate the effect of photosynthetic and stress physiology with UV-B long-term radiation and these effectors co-treatment plants.The main results are as follows:1. The effects of Ca²⁺singal transduction:under 0.15W·m^-2 UV-B mutation, studying on transient changes trend of intracellular Ca²⁺ density in the plant cells and the major avenues of approach main corridor of Ca²⁺ signal transduction system. Results demonstrate that with radiation of UV-B solely, the trend of intracellular Ca²⁺ rises fist and fall later ,interrupt the intracellular IP3 channel,inhibit the liveness of intracellular CaM,the trend of which are blocked to some extent in time-space,however such action is unclear after blocking the Ca²⁺ channel on cytomembrane. These phenomenon show that the density of Ca²⁺ g rowing is mainly caused by intracellular IP3 channel,while the pathway of Ca²⁺/CaM participate in regulating of UV-B.2. The effects of photosynthetic physiology:to investigate the regulational relation between calcium signal system and UV-B radiation in maize, the effects of calcium signal and photosynthesis in maize (Zea mays L) seedlings under0.15W·m^-2 UV-B stress are studied. After different calcium reagent treatment, changes of Ca²⁺ fluorescence intensity, and effects of calcium concentration on the leaf photosynthesis are analyzed. The Ca²⁺fluorescence intensity, increase rapidly when it is treated with UV-B, then decrease and the photosynthesis is inhabited under the UV-B stress. Moreover, when the Maize leaves are treated with the Herpain (intracellular IP3 channel blocker), Trifluoperazine (intracellular CaM activity inhibitor), the increase of Ca²⁺ fluorescence intensity what is stimulated by UV-B is inhabited, then the Hill reaction activity, water use efficiency (WUE), conversion efficiency of primary light energy (Fv/Fm) of PS II, and the potential activity of PSII (Fv/Fo) decreased significantly, finally the reason that the net photosynthetic rate(Pn) decreased. However,LaCl₃ (plasma membrane calcium channel blocker) had less effect on it.Therefore, intercellular IP3/Ca²⁺ system, Ca²⁺/CaM downstream reaction may participate in the chlorophyll content, water utilization, utilization and transfer of light-energy in PSII of maize seedlings leaves under UV-B stress. Ca²⁺ come from intracellular calcium pool have abvious effect on Maize seedlings leaves photosynthesis system.3. The effects of stress physiology:to investigate the regulational relation between calcium signal system and UV-B radiation of 0.15W·m^-2 in maize, the effects of calcium signal and physiological effece in maize (Zea mays L.) seedlings under UV-B stress were studied. After different calcium reagent treatment.The results shows that protein concertration and POD activity increase remarkable when it is treated with UV-B.However, proline concertration and SOD activity decrease and CAT activity increase under U+TFP, SOD activiuty and POD activity increase with the treatment of U+LaCl₃.With different treatment,SOD activity,POD activity and CAT activity reflect different tendency,which show compensation effect..Therefore,when the maize seedlings under the UV-B radiation, plasma membrane release Ca²⁺ and Ca²⁺/CaM downstream reaction,which promote protein concertration and SOD activity increase to protect plants; intercellular IP3 pathway release Ca²⁺,which could increase protein concertration and antioxidant enzyme activity. Ca²⁺ come from plasma membrane calcium channel and intracellular calcium pool have effects on maize seedlings leaves stress physiological reaction to some degree.