大豆异黄酮浸种对盐胁迫大豆幼苗的生理效应

Effects of seed soaking with soybean isoflavones on soybean seedlings under salt stress

大豆异黄酮(Soybean isoflavones)是在大豆生长过程中形成并在成熟种子和叶片中积累较多的一类具有生物活性的次生代谢物,通常可作为人们日常生活中的一类营养保健品。研究了外源大豆苷或染料木苷溶液(0.01 mg/L)浸种处理对盐胁迫栽培大豆(N23674品种)和滩涂野大豆(BB52种群)及其经逐代耐盐性筛选的杂交后代(4076株系,F5)幼苗叶片伤害率、光合作用、Na+含量和Na+/K+值、活性氧清除酶活性及内源大豆异黄酮含量等生理指标的影响。结果表明:盐胁迫下,两种外源大豆异黄酮浸种处理均可显著抑制叶片相对电解质渗透率和硫代巴比妥酸反应物(TBARS)含量的上升及净光合速率(Pn)的下降,降低Na+含量和Na+/K+值,增强超氧化物歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性,提高内源大豆异黄酮含量,从而表现对盐害的缓解效应,其中对耐盐性较弱的栽培大豆N23674品种效应更明显。这为大豆异黄酮在大豆耐盐育种、化学调控和盐碱地种植利用等提供了理论依据。

Soil salinity is one of the major abiotic stresses that adversely affect crop productivity and quality.The pathways for improving plant salt tolerance may include salt hardening,chemical regulation and genetic engineering breeding.Soybean isoflavones are one type of natural and bioactive metabolites that synthesize and accumulate in seeds and leaves during soybean development,and often function as an important dietary constituent in human nutrition and health protection.In general,the contents of soybean isoflavones in seeds of Glycine soja are higher than those in Glycine max,and the contents of soybean isoflavones are positively correlated to the salt tolerance of soybean plants.The exogenous application（such as seed soaking,solution culture and foliar spraying） of some bioactive substances（such as calcium ion,ABA and polyamines） is a kind of simple and effective approach to improve the plant stress tolerance in agricultural practice.However,the effects of seed soaking with exogenous soybean isoflavones on soybean seedlings under salt stress condition and its physiological mechanisms are still not reported up to date.Daidzin and genistin are two major components of soybean isoflavones that accumulate in seeds of soybean.In this study,the Glycine max N23674 cultivar,the salt-born Glycine soja BB52 population and their hybrid 4076 strain（F5） were used as the experimental materials.The hybrid 4076 strain（F5） was selected for salt tolerance generation by generation from the cross combination of N23674×BB52.The effects of seed soaking with exogenous soybean isoflavones（0.01 mg/L Daidzin or Genistin） on the leaf salt injury,photosynthesis,Na＋ content and Na＋/K＋ ratio,activities of reactive oxygen species（ROS） scavenging enzymes and contents of endogenous soybean isoflavones were investigated.The results showed that,the treatments of seed soaking with Daidzin or Genistin could all significantly inhibited the increases of relative electrolytic leakage and content of thiobarbituric acid reactive substances（TBARS）,and the decrease of net photosynthetic rate（Pn）,reduced the Na＋content and Na＋/ K＋ ratio,and enhanced the activities of superoxide dismutase（SOD）,peroxidase（POD） and catalase（CAT） and the contents of endogenous soybean isoflavones in leaves of the NaCl-stressed seedlings,and therefore displayed the alleviated effects on soybean salt injury,especially for the salt sensitive Glycine max N23674 cultivar.So,the treatment of seed soaking with exogenous soybean isoflavones（Daidzin or Genistin） is able to improve the salt tolerance of soybean seedlings,which is possibly reached through the maintenance of leaf photosynthesis,increasing the contents of its endogenous soybean isoflavones,enhancing the scavenging ability of its ROS to maintain the cell membrane integrity,and regulating the absorption and transportation of salt ions to reduce the ionic toxicity.Thus the seed soaking with exogenous soybean isoflavones may be a usable approach to enhance the cultivated soybean salt tolerance in practice.The above-mentioned may provide the theoretic basis for the research of soybean isoflavones in chemical regulation of soybean salt tolerance,the breeding of salt-tolerant soybean cultivar,and the utilization of saline land in the future.