外源水杨酸预处理对低温胁迫下甜瓜幼苗生长及其抗逆生理特性的影响

Effects of Exogenous Salicylic Acid Pretreatment on Growth and Resistance Physiological Indexes in Melon Seedling under Chilling Stress

以甜瓜品种‘红优’幼苗为试验材料,在人工气候箱内采用基质栽培法,对其叶面喷施不同浓度(0.1、0.5、1.0、2.0mmol·L^(-1))水杨酸(SA),研究SA预处理对低温(昼12℃/夜6℃)胁迫7d及恢复7d后甜瓜幼苗生长、叶绿素含量、渗透调节物质含量以及抗氧化系统的影响。结果表明:(1)低温胁迫能明显抑制甜瓜幼苗的生长,外源施用不同浓度SA预处理均能缓解低温对甜瓜幼苗的伤害,并以1.0mmol·L^(-1) SA作用最明显,且显著提高了低温胁迫下甜瓜幼苗的株高、茎粗、地上鲜重和叶绿素含量。(2)适宜浓度的外源SA预处理可明显提高低温胁迫下甜瓜幼苗叶片的渗透调节物质可溶性糖、可溶性蛋白和脯氨酸的含量,增强其渗透调节作用。(3)低温胁迫下外源SA预处理能够诱导提高甜瓜幼苗叶片中超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化酶(APX)、谷胱甘肽还原酶(GR)和脱氢抗坏血酸还原酶(DHAR)的活性,增加甜瓜幼苗叶片中抗坏血酸(ASA)、谷胱甘肽(GSH)含量、ASA/DHA及GSH/GSSG,从而有效降低叶片电解质渗透率、丙二醛(MDA)和活性氧(ROS)含量。研究发现,适宜浓度的外源SA预处理,能够在低温胁迫条件下通过增加渗透调节物质的含量,诱导增强抗氧化酶活性,以及激活ASA-GSH循环系统,促进甜瓜幼苗的生长,从而提高甜瓜幼苗的耐低温性能。

The aim of the study was to investigate the effect of exogenous salicylic acid(SA)pretreatment on the growth,chlorophyll contents,osmotic adjustment substance contents and antioxidant system of melon seedlings under chilling stress(12℃/6℃)and 7days’recovery condition(28℃/22℃).Cultivar‘Hongyou’seedlings were treated with different concentrations of SA(including0.1,0.5,1.0and2.0mmol·L-1)in climate chambers.The results showed that:(1)chilling stress significantly inhibited the growth of melon seedlings,different concentrations of exogenous SA pretreatment could alleviate the damage induced by chilling stress,and 1.0mmol·L^-1SA has the most notable effect.1.0mmol·L^-1SA significantly increased plant height,stem thickness,and fresh weight of melon seedlings.(2)Suitable exogenous SA pretreatment also increased soluble sugar,soluble protein and proline contents,promoted osmotic adjustment.(3)In addition,exogenous SA pretreatment could strengthen the activities of superoxide dismutase(SOD),peroxidase(POD),catalase(CAT),ascorbate peroxidase(APX),glutathione reductase(GR)and dehydroascorbate reductase(DHAR),increase the contents of ascorbic acid(AsA)and glutathione(GSH),improve the ratios of ASA/DHA and GSH/GSSG,so the electrolyte leakage,malondialdehyde(MDA)content and reactive oxygen species(ROS)greatly reduced.Overall,appropriate concentration of exogenous SA pretreatment could promote the growth and chilling tolerance of melon seedlings,through increasing osmotic adjustment substance contents,enhancing antioxidant enzyme activities and activating AsA-GSH cycle.