Li Hao, Chang Jingjing, Chen Hejie, Wang Zhongyuan, Gu Xiurong, Wei Chunhua, Zhang Yong, Ma Jianxiang, Yang Jianqiang, Zhang Xian
College of Horticulture, Northwest A&F University Yangling, China.
Front Plant Sci. 2017 Mar 1;8:295. doi: 10.3389/fpls.2017.00295. eCollection 2017.
Melatonin, a pleiotropic signal molecule, has been shown to play important roles in the regulation of plant growth, development, and responses to environmental stresses. Since a few species have been investigated to unveil the effect of exogenous melatonin on salt stress, the underlying mechanism of melatonin-mediated salt stress tolerance in other plant species still remains largely unknown. In this study, the effects of melatonin on leaf photosynthesis and redox homeostasis in watermelon were examined under salt stress (300 mM NaCl) along with different doses of melatonin (50, 150, and 500 μM) pretreatment. NaCl stress inhibited photosynthesis and increased accumulation of reactive oxygen species and membrane damage in leaves of watermelon seedlings. However, pretreatment with melatonin on roots alleviated NaCl-induced decrease in photosynthetic rate and oxidative stress in a dose-dependent manner. The protection of photosynthesis by melatonin was closely associated with the inhibition of stomatal closure and improved light energy absorption and electron transport in photosystem II, while the reduction of oxidative stress by melatonin was attributed to the improved redox homeostasis coupled with the enhanced activities of antioxidant enzymes. This study unraveled crucial role of melatonin in salt stress mitigation and thus can be implicated in the management of salinity in watermelon cultivation.
褪黑素是一种多效性信号分子，已被证明在调节植物生长、发育以及对环境胁迫的响应中发挥重要作用。由于仅对少数物种进行了研究以揭示外源褪黑素对盐胁迫的影响，因此褪黑素介导其他植物物种耐盐胁迫的潜在机制在很大程度上仍然未知。在本研究中，在盐胁迫（300 mM NaCl）以及不同剂量褪黑素（50、150和500 μM）预处理条件下，检测了褪黑素对西瓜叶片光合作用和氧化还原稳态的影响。NaCl胁迫抑制了西瓜幼苗叶片的光合作用，增加了活性氧的积累和膜损伤。然而，对根系进行褪黑素预处理以剂量依赖的方式减轻了NaCl诱导的光合速率下降和氧化胁迫。褪黑素对光合作用的保护与气孔关闭的抑制以及光系统II中光能吸收和电子传递的改善密切相关，而褪黑素对氧化胁迫的减轻归因于氧化还原稳态的改善以及抗氧化酶活性的增强。本研究揭示了褪黑素在缓解盐胁迫中的关键作用，因此可应用于西瓜栽培中的盐度管理。
