外施褪黑素对低温胁迫下红树植物秋茄光合作用和抗坏血酸-谷胱甘肽循环的调控

Melatonin regulates photosynthesis and ascorbate-glutathione cycle in a mangrove Kandelia obovata under low temperature stress

采用叶面喷施方式,研究外施不同浓度褪黑素(MEL)预处理对低温胁迫下秋茄叶片光合作用及抗氧化代谢的影响。结果表明,低温胁迫降低了秋茄叶片抗氧化酶(POD、APX、GR、DHAR、MDHAR)活性和抗氧化剂(AsA、GSH)含量,加速了ROS (O2^-·和H2O2)积累,提高了MDA含量和相对电导率,抑制了叶片光合能力。外施MEL能提高低温胁迫下秋茄叶片Pn、Gs、Tr、ΦPSII、Fv/Fm和qP,反而降低Ci和NPQ。同时, MEL也能提高低温胁迫下秋茄叶片上述抗氧化酶活性和抗氧化剂含量,增加AsA/DHA、GSH/GSSG比值,抑制ROS大量产生,减少膜系统伤害。总之,外施MEL可通过提高AsA-GSH循环中抗氧化酶活性,增强清除ROS能力,减轻秋茄叶片PSII光抑制,从而提高植株光合作用。其中当MEL浓度为100μmol·L^-1时,喷施调控效果最佳。

After Kandelia obovata seedlings were pre-treated with spraying melatonin(MEL),we investigated the influences of melatonin on the photosynthesis and antioxidant metabolism under low temperature stress.The results showed that low temperature stress apparently decreased the leaf activities of POD,APX,GR,DHAR,MDAR and contents of AsA and GSH,whereas accelerated the accumulation of ROS(O2^-· and H2O2) and increased MDA content and relative electrical conductivity.Consequently,low temperature stress depressed leaf photosynthetic capacity.However,MEL could increase leaf Pn,Gs,Tr,ΦPSII,Fv/Fm and qP,while decrease leaf Ci and NPQ under low temperature stress.Meanwhile,MEL improved activities of the above-mentioned antioxidant enzyme and antioxidant contents under low temperature stress,and increased ratios of AsA/DHA and GSH/GSSG,but decreased the accumulation of ROS and injury of membrane system.Thus,MEL could improve photosynthesis and cold tolerance of Kandelia obovata.All the findings demonstrate that foliar spraying of MEL at 100 μmol L-1 performs most appropriate practice to improve cold tolerance of Kandelia obovata.