24-表油菜素内酯对盐碱胁迫下大豆生育、生理及细胞超微结构的影响

【目的】探讨外源EBR(24-表油菜素内酯)对盐碱复合胁迫下大豆的生长指标、生理特性及超微结构的影响,为改善大豆生长、保障粮食安全、实现农业可持续发展奠定基础。【方法】以大豆品种黑农44号为试材,分别在110 mmol·L~(-1)的盐碱复合胁迫条件下培养3 d和7 d进行取材,研究1.2 mg·L~(-1)外源EBR对大豆株高、根系生长,叶片3种抗氧化酶超氧化物歧化酶(superoxide dismutase,SOD)、过氧化物酶(peroxidase,POD)及抗坏血酸过氧化物酶(ascorbate peroxidase,APX)活性,相对电导率、超氧阴离子(O_2~-)产生速率、过氧化氢(H_2O_2)和丙二醛(malondialdehyde,MDA)含量、游离脯氨酸和叶绿素含量以及叶片和根尖细胞超微结构的影响。【结果】盐碱胁迫处理3 d和7 d时,与对照组相比,3种抗氧化酶(SOD、POD、APX)的活性、游离脯氨酸含量、相对电导率、O_2~-产生速率、H_2O_2和MDA含量均升高;各项生长指标、叶绿素含量均降低;叶片细胞结构中叶绿体和线粒体遭到严重破坏;根尖细胞中线粒体、内质网结构破坏较重,液泡破裂。盐碱胁迫条件下,施加外源EBR使大豆的株高、根长和根鲜重分别提高了6.45%、9.60%和19.85%;使大豆叶片SOD、POD、APX的活性显著升高,在3 d和7 d时分别增加了16.92%和9.68%、48.85%和61.44%、19.05%和20.36%;相对电导率、O_2~-产生速率、H_2O_2和MDA的含量显著降低,分别降低了19.58%和28.26%、28.06%和40.92%、28.62%和31.21%、31.03%和37.17%;脯氨酸和叶绿素含量显著升高,分别升高了3.67%和15.96%、13.34%和16.87%;同时维护了大豆叶片和根尖细胞超微结构的稳定性,延缓了细胞的衰老、解体。【结论】在盐碱胁迫下,施加外源EBR通过提高抗氧化酶活性和脯氨酸及叶绿素含量,降低了活性氧(ROS)的积累,维护了细胞结构的完整,促进了幼苗生长,增强了大豆幼苗耐盐碱胁迫的能力。

Effects of 24-Brassinolide on the Fertility,Physiological Characteristics and Cell Ultra-Structure of Soybean Under Saline-Alkali Stress

【Objective】The aim of this experiment was to study the effects of exogenous EBR (24-epibrassinolide) on the growth indices, physiological characteristics and cellular ultrastructure of soybean under saline-alkali stress. 【Method】Soybean variety Heinong 44 was employed as the test material, and cultivated in 110 mmol·L^-1 nutrient solution saline-alkali stress treatments for 3 d and 7 d to investigate the effects of 1.2 mg·L^-1 exogenous EBR on the height and root growth, SOD, POD, and APX three kinds of antioxidant enzyme activities, relative electrical conductivity, superoxide anion (O₂^-) production rate, contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA), free proline concentration content, chlorophyll content of soybean leaves and the responses of cellular ultrastructure of soybean leaves and root tips under saline-alkali stress. 【Result】Under the condition of saline-alkali stress dealing with 3 d and 7 d, compared to the control, the three kinds of antioxidant enzyme activities of SOD, POD, and APX, free proline content, relative electrical conductivity, O₂^-production rate, contents of H₂O₂ and MDA all increased, the growth indices and chlorophyll content all decreased; the chloroplast and mitochondria cellular ultrastructure of soybean leaves suffered severe damages. The mitochondria and endoplasmic reticulum cellular ultrastructure of soybean root tips suffered severe damages, and vacuole was ruptured. Application of EBR under saline-alkali stress increased soybean plant height, root length, fresh mass of root by 6.45%, 9.60% and 19.85%, respectively. Application of EBR the activities of SOD, POD, and APX of soybean leaves in 3 d and 7 d treatments increased by 16.92% and 9.68%, 48.85% and 61.44%, 19.05% and 20.36%, respectively, relative electrical conductivity, O₂^-production rate, H₂O₂ and MDA contents significantly decreased by 19.58% and 28.26%, 28.06% and 40.92%, 28.62% and 31.21%, 31.03% and 37.17%, respectively, free proline content and chlorophyll content significantly increased by 3.67% and 15.96%, 13.34% and 16.87%, respectively. At the same time, the stability of soybean leaves and root tip cell ultrastructure were maintained and the aging of cells and disintegration were delayed.【Conclusion】The results suggested that application of exogenous EBR under saline-alkali stress could increase the antioxidant enzyme activities, free proline concentration and chlorophyll content, reduce the accumulation of reactive oxygen species(ROS), maintain the cell structure integrity, promote seedling growth and resulting in improving the tolerance of soybean seedlings to saline-alkali stress.