外源褪黑素对盐胁迫下两种紫花苜蓿生理及光合特性的影响

Implications of Exogenous Melatonin on the Physiological and Photosynthetic Characteristics of the Seedlings of Two Alfalfa Varieties

为探究外源褪黑素(Melatonin,MT)对盐胁迫下紫花苜蓿(Medicago sativa L.)生理及光合特性的影响,本研究以紫花苜蓿‘中苜1号’(耐盐)和‘渭南’(敏盐)为材料,根施浓度为25(MT1),50(MT2),70(MT3),100(MT4),150(MT5)μmol·L^(-1)的褪黑素预处理,用浓度为150 mmol·L^(-1)的盐溶液胁迫并分析处理前后紫花苜蓿幼苗生理及光合指标。结果表明:150 mmol·L^(-1)盐浓度使植株生长受明显抑制,当褪黑素浓度为50,70,100μmol·L^(-1)时可显著提高盐胁迫下2种紫花苜蓿幼苗叶片相对含水量、脯氨酸和叶绿素含量,降低相对电导率和丙二醛含量;各浓度褪黑素处理均显著提高2种紫花苜蓿的超氧化物歧化酶、过氧化氢酶、过氧化物酶活性。50,70,100μmol·L^(-1)MT处理显著提高2种紫花苜蓿的净光合速率、气孔导度、胞间CO 2浓度和蒸腾速率。外源褪黑素浓度为100μmol·L^(-1)时对缓解紫花苜蓿受盐胁迫伤害效果最佳。

To investigate the effects of exogenous Melatonin(MT)on alfalfa’s response to salt stress,two varieties of alfalfa,‘Zhongmu No.1’(salt-tolerant)and‘Weinan’(salt-sensitive)were selected and the seedlings roots were pre-treated with the concentrations 25(MT1),50(MT2),70(MT3),100(MT4),and 150(MT5)μmol·L^(-1)melatonin.After pretreatment,all seedlings of the pretreated and control-check were transferred into 150 mmol·L^(-1)salt solution for salt stress,and the physiological and photosynthetic characters were investigated.The results showed that the MT concentration of 150 mmol·L^(-1)inhibited the seedling growth significantly of two varieties.The pretreatments of melatonin concentration of 50,70,100μmol·L^(-1),the relative water content,proline and chlorophyll contents of the seedling leaves of two alfalfa varieties under salt stress were significantly increased,and the relative electrical conductivity and Malondialdehyde content were decreased.The activity of Superoxide dismutase(SOD),Catalase(CAT)and Peroxidase(POD)in the seedling leaves of two varieties were significantly increased;the net photosynthetic rate(Pn),stomatal conductance(Gs),intercellular CO 2 concentration(Ci)and transpiration rate(Tr)of the seedlings of two varieties also significantly enhanced.It could be concluded that exogenous melatonin concentration of 100μmol·L^(-1)had the best effect on relieving the injury of alfalfa under salt stress.