外源CaCl2预处理对高温胁迫烟草叶片光合作用的影响

 【目的】研究喷施不同浓度CaCl2对高温胁迫下烟草叶片光合荧光特性及活性氧清除酶系统的影响,探讨外源Ca2+对高温胁迫下烟草叶片光合作用的保护机制。【方法】以烟草品种K326为材料,喷施0、10、20、30 mmol?L-1CaC12,43℃高温处理2 h,测定处理前后及恢复1 d 后烟草叶片光合速率、叶绿素荧光诱导动力学曲线、丙二醛(MDA)含量、过氧化氢(H2O2)含量和抗氧化酶活性等生理指标。【结果】高温胁迫下,CaCl2处理缓解了净光合速率(Pn)和PSII最大光化学效率(Fv/Fm)的降低程度。施钙显著缓解了PSII反应中心电子传递受阻程度和放氧复合体受破坏的程度,使PSII维持较高的活性。施钙明显激活了高温胁迫下烟草叶片超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)和抗坏血酸过氧化物酶(APX)的活性,减少了H2O2的积累;膜脂过氧化产物MDA含量显著降低。以喷施20 mmol?L-1 CaCl2时,烟草叶片的抗氧化酶活性较高,光合活性最高。【结论】施钙增强了烟草叶片抗氧化酶活性,H2O2的积累降低,从而减轻了高温胁迫对烟草叶片PSII反应中心和放氧复合体(OEC)的破坏,提高了烟草叶片的耐热性。

Alleviative Effects of Exogenous CaCl_2 on the Inhibition of Photosynthesis Induced by Heat Stress in Tobacco

Objective] The effects of CaCl_2 on photosynthesis and antioxidative enzyme activities in tobacco under high temperature stress were investigated to reveal the mechanism of external Ca~(2+) enhances the thermotolerance of tobacco plants. Method] The K326 tobacco plants were sprayed with different concentrations (0, 10, 20, 30) of CaCl_2 for four days, at the fifth day exposed to 43"C for 2 hours, then returned to normal growth condition for one day recovery. Photosynthetic rate, chlorophyll fluorescence transients (OJIP), MDA content, H_2O_2 content and the activities of antioxidative enzymes were studied during the process. Result] Under heat stress, CaCl_2 pretreatment greatly reduced the decrease in net photosynthesis rate (Pn) and maximum photochemical efficiency of PS II (Fv/Fm). Moreover, it alleviated the damage of heat stress to electron transportation of PSII center and oxygen-evolving complex, so that the PSII could maintain high activity. CaCl_2 pretreatment also greatly enhanced the activities of SOD, POD, CAT and APX, reduced the accumulation of H_2O_2, and thus, the active oxygen species were scavenged efficiently; the accumulation of final product of membrane lipid peroxidation (MDA) greatly decreased. The tobacco plants pretreated with 20 mmol·L~(-1) CaCl_2 maintained the highest antioxidant enzymes activities and photosynthetic ability. Conclusion] CaCl_2 pretreatment alleviated the heat stress damage to PSII center and oxygen evolving complex via enhancing the antioxidant enzymes activities, reducing the accumulation of H_2O_2 and protecting the membrane from peroxidation. Exogenous CaCl_2 application enhanced thermotolerance of tobacco plants under high temperature stress.