H_(2)O_(2)浸种对盐胁迫下紫花苜蓿种子萌发和幼苗生长的影响

Effects of H_(2)O_(2)immersion on seed germination and seedling growth of alfalfa under salt stress

盐胁迫是全球范围内影响植物正常生长的主要非生物胁迫之一,外源H_(2)O_(2)可以通过调节植物过氧化酶活性及渗透调节物质含量来缓解盐胁迫对植物造成的伤害。本研究通过设置不同盐胁迫浓度(0,0.6%,1.2%,1.8%NaCl)及H_(2)O_(2)浸种处理(0、5、100μmol·L^(-1)H_(2)O_(2)),研究H_(2)O_(2)浸种对不同浓度盐胁迫下紫花苜蓿种子萌发、幼苗生长、抗氧化酶活性及渗透调节物质的影响。结果表明:1)随着NaCl浓度的增加,苜蓿种子的发芽率、发芽势、发芽指数和活力指数均逐渐降低;苜蓿苗和全株的鲜重、干重、绝对含水量先增后减,根的鲜重、干重、绝对含水量逐渐减小;超氧化物歧化酶(SOD)活性和可溶性蛋白含量逐渐增加,过氧化氢酶(CAT)活性和丙二醛含量先增后减,过氧化物酶(POD)活性和可溶性糖含量均低于无盐胁迫。2)H_(2)O_(2)浸种提高了苜蓿种子的发芽势、发芽指数和活力指数。5μmol·L^(-1)H_(2)O_(2)浸种处理下,苜蓿苗、根和全株的鲜重、干重、根冠比以及幼苗的SOD和CAT活性、脯氨酸和可溶性蛋白含量均高于100μmol·L^(-1)H_(2)O_(2)和蒸馏水浸种处理,而丙二醛含量为5μmol·L^(-1)H_(2)O_(2)浸种处理低于100μmol·L^(-1)H_(2)O_(2)和蒸馏水浸种处理。综合分析表明,盐胁迫抑制了苜蓿种子的萌发和幼苗生长,苜蓿通过提高自身抗氧化酶活性和渗透调节物质含量来抵御盐胁迫;H_(2)O_(2)浸种提高了苜蓿种子和幼苗的抗盐能力,且5μmol·L^(-1)H_(2)O_(2)浸种优于100μmol·L^(-1)H_(2)O_(2)浸种。

Salt stress is one of the major abiotic stresses affecting the normal growth of plants worldwide.Exogenous H_(2)O_(2)can alleviate the damage caused by salt stress on plants by altering the activity of plant peroxidase and osmotic regulatory substances.In this study,different salt stress concentrations(0,0.6%,1.2%,1.8%NaCl)and H2O2 immersion seed treatments(0,5,100μmol·L^(−1)H_(2)O_(2))were used to study the effects of H_(2)O_(2)on seed germination,seedling growth,antioxidant enzyme activity and osmotic adjustment substances of alfalfa under the different salt stress concentrations.It was found that:1)With successive increases in NaCl concentration,the germination rate,germination potential,germination index and vigor index of alfalfa seed progressively decreased.With increase in NaCl concentration,the fresh weight,dry weight and absolute water content of alfalfa seedlings aboveground and whole plant initially increased and then decreased at higher concentration,while the fresh weight,dry weight and absolute water content of roots continued to decrease across the tested concentration range.With increasing NaCl concentration,superoxide dismutase(SOD)activity and soluble protein content increased gradually,catalase(CAT)activity and malondialdehyde content increased initially and then decreased,peroxidase(POD)activity and soluble sugar contents were lower than those of seedlings without salt stress.2)The germination potential,germination index and vigor index of alfalfa seed were improved by H_(2)O_(2)immersion.The fresh weight,dry weight,root∶shoot,SOD and CAT activities,proline and soluble protein contents of alfalfa seedlings under the 5μmol·L^(−1)H_(2)O_(2)immersion treatment were higher than those under the 100μmol·L^(−1)H_(2)O_(2)and distilled water immersion treatments,while the malondialdehyde content of the 5μmol·L^(−1)H_(2)O_(2)treatment was lower than that of 100μmol·L^(−1)H_(2)O_(2)and distilled water immersion treatments.Multivariate analysis showed that salt stress inhibited seed germination and seedling growth of alfalfa,and that alfalfa seedlings resisted salt stress by increasing antioxidant enzyme activity and osmotic regulatory substance content.The salt resistance of alfalfa seeds and seedlings was improved by H_(2)O_(2)immersion,and soaking seeds with 5μmol·L^(−1)H_(2)O_(2)was better than soaking with 100μmol·L^(−1)H_(2)O_(2).