Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Wuhan, 430062, China; State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Shuangqing Road 18, Haidian Distract, Beijing, 100085, China; College of Resources and Environment, University of Chinese Academy of Sciences, Shijingshan Disctrict, Beijing, 100049, China.
Oil Crops Research Institute, Chinese Academy of Agricultural Sciences, Wuhan, 430062, China.
Plant Physiol Biochem. 2020 Apr;149:86-95. doi: 10.1016/j.plaphy.2020.01.039. Epub 2020 Feb 3.
Two contrasting rapeseed (Brassica napus L.) genotypes, Qinyou 8 (drought-sensitive) and Q2 (drought-tolerant), were studied under drought stress with or without pretreatment with melatonin to (i) explore whether melatonin enhances drought resistance by regulating root growth and (ii) determine the relationship between the belowground and aboveground responses to melatonin under drought stress. Results show that the light-saturated rate of photosynthesis (P), stomatal conductance (g), water use efficiency (WUE) and chlorophyll content were decreased by drought for Qinyou 8, whereas drought only decreased P and chlorophyll content for Q2. Drought decreased actual photochemical efficiency in saturated light (F'/F'), actual photochemical efficiency (PhiPSⅡ), quenching of photochemical efficiency (qL) and electron transport rate (ETR) in Qinyou 8. However drought only decreased F'/F' and qL in Q2. Drought increased malondialdehyde (MDA) and hydrogen peroxide (HO) contents in the roots of both genotypes. Melatonin had no significant additional effects on root guaiacol peroxidase (POD) and superoxide dismutase (SOD) activities, but enhanced root catalase (CAT) activity of droughted plants further. Melatonin promoted taproot and lateral root growth under drought stress. Melatonin also promoted stomatal opening resulting in enhanced photosynthesis in the two genotypes. The two mechanisms induced by melatonin synergistically enhance drought resistance of rapeseed as indicated by enhanced gas exchange parameters under melatonin pretreatment. The findings provide evidence for a physiological role of melatonin in improving drought resistance, especially in belowground parts.
两种不同的油菜（甘蓝型油菜）基因型，秦优 8 号（抗旱敏感型）和 Q2（抗旱型），在有或没有褪黑素预处理的情况下进行干旱胁迫研究，（i）探讨褪黑素是否通过调节根系生长来增强抗旱性，以及（ii）确定在干旱胁迫下褪黑素对地下和地上部分的反应之间的关系。结果表明，干旱对秦优 8 号的光合作用光饱和速率（P）、气孔导度（g）、水分利用效率（WUE）和叶绿素含量都有降低作用，而干旱只对 Q2 降低了 P 和叶绿素含量。干旱降低了秦优 8 号的饱和光下实际光化学效率（F'/F'）、实际光化学效率（PhiPSⅡ）、光化学效率的猝灭（qL）和电子传递速率（ETR）。然而，干旱只降低了 Q2 中的 F'/F'和 qL。干旱增加了两种基因型根中的丙二醛（MDA）和过氧化氢（HO）含量。褪黑素对根中愈创木酚过氧化物酶（POD）和超氧化物歧化酶（SOD）活性没有显著的额外影响，但进一步增强了干旱植物的根过氧化氢酶（CAT）活性。褪黑素促进了在干旱胁迫下主根和侧根的生长。褪黑素还促进了气孔的开放，导致两种基因型的光合作用增强。这两种由褪黑素诱导的机制协同增强了油菜的抗旱性，特别是在地下部分。这些发现为褪黑素在提高抗旱性方面的生理作用提供了证据，特别是在地下部分。
