叶面喷施褪黑素对干旱及复水下玉米光合特性和抗氧化系统的影响

Effect of Foliar Spraying Melatonin on Photosynthesis and Antioxidant System of Maize Leaves under Drought Stress and Rewatering

为揭示叶面喷施外源褪黑素(MT)在干旱胁迫及复水下调控玉米的生理机制,该研究以玉米‘陕科9号’为试验材料,叶面喷施100μmol·L^(-1)褪黑素,在重度干旱胁迫和复水后测定叶片相对含水量(RWC)、叶面积、地上部生物量、光合机构活性以及抗氧化酶活性等指标。结果表明:(1)外源喷施褪黑素能有效缓解干旱胁迫诱导的玉米生长发育抑制,同时显著提高干旱胁迫下玉米叶片光系统(PSⅡ和PSⅠ)有效量子产量[Y(Ⅱ)和Y(Ⅰ)],并降低干旱胁迫下叶片PSⅠ受体侧和供体侧限制引起的非光化学能量耗散的量子产量Y(ND)和Y(NA)。(2)喷施外源褪黑素显著增强了干旱胁迫玉米植株叶片超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、抗坏血酸过氧化物酶(APX)及谷胱甘肽还原酶(GR)活性,显著降低了其丙二醛(MDA)和过氧化氢(H2O2)含量;同时外源褪黑激素也显著上调了其相应抗氧化酶活性相关基因的表达量。(3)复水后,干旱胁迫下经褪黑素处理的玉米植株叶片上述各参数恢复速度较单独干旱胁迫处理植株更快。研究认为,叶面喷施褪黑素有效缓解了干旱胁迫对玉米叶片的光合机构的损伤,增强了叶片抗氧化酶活性及相关基因的表达,显著降低了膜脂过氧化伤害程度,且复水后显著促进叶片生理功能的恢复,表明外源褪黑素可通过改善干旱及复水下玉米叶片光合效率和抗氧化能力,从而促进植株生长以适应干旱多变的环境。

In the present study,we investigated the physiological mechanism of foliar spraying of exogenous melatonin(MT)on maize under drought stress and rewatering.The maize cultivar‘Shaanke No.9’applied with 100μmol·L^(-1) melatonin was used as the experimental materials,the changes of leaf relative water content(RWC),leaf area,aboveground biomass,photosynthetic characteristics and antioxidant enzyme activities were determined under severe drought stress and rewatering.The results suggested that:(1)foliar application of exogenous melatonin could alleviate the maize growth inhibited by drought stress.It also improved the effective quantum yield of PSⅡand PSⅠunder drought stress[Y(Ⅱ),Y(Ⅰ)],decreased the PSⅠreceptor side limitation[Y(NA)]and donor side limitation[Y(ND)]of leaf photosynthetic apparatus after drought stress.(2)The melatonin-treated plants exhibited lower malondialdehyde(MDA)content and hydrogen peroxide(H2O2)content.The activities of superoxide dismutase(SOD),catalase(CAT),ascorbate peroxidase(APX)and glutathione reductase(GR)were enhanced and the expression of antioxidant enzymes related genes were upregulated by melatonin treatment under drought stress.(3)After rehydration,compared with untreated maize,higher recovery rates of parameters were obverted in exogenous melatonin-treated maize leaves.Consequently,foliar spraying of melatonin effectively alleviated the damage to photosynthetic apparatus of maize leaves under drought stress,enhanced the activities of antioxidant enzymes and the expression of related genes,significantly reduced the level of membrane lipid peroxidation,and substantially promoted the recovery of physiological functions of maize leaves after rehydration.In short,exogenous melatonin can improve the photosynthetic efficiency and antioxidant capacity of maize leaves under drought and recovery water,eventually promoting the plant growth to adapt to the stress environments.