外源褪黑素缓解甜高粱幼苗干旱胁迫的生理效应

Exogenous melatonin alleviates the physiological effects of drought stress in sweet sorghum seedlings

为探究外源褪黑素缓解甜高粱幼苗干旱胁迫可能的生理机制,以甜高粱品种‘大力士’为材料,采用盆栽试验方法,分析自然干旱条件下,叶面喷施褪黑素(100 μmol·L^(-1))对甜高粱幼苗生长及生理特性的影响。结果表明,干旱胁迫导致植株地上部水分失衡,叶绿体结构受损,细胞产生氧化胁迫,显著抑制甜高粱幼苗的生长。喷施褪黑素可显著降低甜高粱叶片丙二醛(MDA)含量,积累更多的可溶性蛋白和脯氨酸,提高叶片含水量,使叶绿体基粒片层排列有序,光合色素含量升高;喷施褪黑素还能显著提高叶片过氧化物酶(POD)和硝酸还原酶活性。综合上述,喷施100 μmol·L^(-1)褪黑素能进一步激发干旱环境中甜高粱叶片抗氧化系统的保护作用,通过渗透调节,维持植株水分平衡,改善叶绿体结构,提高光合色素含量,协同增强氮代谢,促进植株生长,从而缓解干旱对甜高粱幼苗的伤害。

In order to explore the possible physiological mechanism of exogenous melatonin alleviation of drought stress in sweet sorghum seedlings,a pot experiment was set up to investigate the effects of spraying melatonin(100μmol·L^(−1))on the growth and physiological characteristics of‘Dalish’sweet sorghum seedlings under natural drought conditions.It was found that drought stress resulted in water imbalance in plant shoots,damaged the chloroplast structure and produced intracellular oxidative stress,which significantly inhibited the growth of the sweet sorghum seedlings.Spraying 100μmol·L^(−1) melatonin significantly reduced the malondialdehyde content in leaves,facilitated increased accumulation of soluble protein and proline,increased the water content of leaves,promoted orderly arrangement of the granula lamellae of chloroplast,and increased the content of photosynthetic pigment.Spraying melatonin also significantly increased the activities of peroxidase and nitrate reductase in leaves.In conclusion,spraying 100μmol·L^(−1) melatonin enhanced the protective effect of antioxidant systems in sweet sorghum leaves under drought conditions,which helped to maintain plant water balance,improve chloroplast structure and increase the photosynthetic pigment content through osmotic regulation and synergistically enhanced nitrogen metabolism.At the same time,exogenous melatonin enhanced nitrogen metabolism and promoted the plant growth,resulting in alleviation of drought damage to sweet sorghum seedlings.