中国农业科学 ›› 2018, Vol. 51 ›› Issue (5): 868-882.doi: 10.3864/j.issn.0578-1752.2018.05.006

• 耕作栽培·生理生化·农业信息技术 • 上一篇    下一篇

干旱胁迫对不同抗旱性苜蓿品种根系生长及生理特性影响

张翠梅,师尚礼,吴芳   

  1. 甘肃农业大学草业学院/草业生态系统教育部重点实验室/甘肃省草业工程实验室/中-美草地畜牧业可持续研究中心 兰州 730070
  • 收稿日期:2017-07-14 出版日期:2018-03-01 发布日期:2018-03-01
  • 通讯作者: 师尚礼,E-mail:shishl@gsau.edu.cn
  • 作者简介:张翠梅,E-mail:Zhangcm1710@163.com
  • 基金资助:
    牧草种质资源保护与利用(NB2130135)

Effects of Drought Stress on Root and Physiological Responses of Different Drought-Tolerant Alfalfa Varieties

ZHANG CuiMei, SHI ShangLi, WU Fang   

  1. College of Grassland Science, Gansu Agricultural University/Key Laboratory of Grassland Ecosystem, Ministry of Education/Pratacultural Engineering Laboratory of Gansu Province/Sino-US Centers for Grazingland Ecosystem Sustainability, Lanzhou 730070
  • Received:2017-07-14 Online:2018-03-01 Published:2018-03-01

摘要: 【目的】研究干旱胁迫对不同抗旱性苜蓿品种根系生长特征及生理特性的影响,明确不同抗旱性苜蓿品种响应干旱胁迫的生长及生理差异,为进一步阐明紫花苜蓿抗旱的分子机理、提高紫花苜蓿耐旱性和水分利用效率提供理论依据。【方法】采用营养液沙培法,选用强抗旱的陇中苜蓿(Medicago sativa L. cv. Longzhong)、中抗旱的陇东苜蓿(Medicago sativa L. cv. Longdong)和弱抗旱的甘农3号紫花苜蓿(Medicago sativa L. cv. Gannong No.3)为试验材料,在幼苗期对其进行6种不同水势(0、-0.4、-0.8、-1.2、-1.6和-2.0 MPa)的PEG-6000人工模拟干旱胁迫,研究干旱胁迫对供试苜蓿根系生长特征(根系总长度、根系总表面积、根系平均直径、根体积、根尖数和根系干重)、根系活力、游离脯氨酸(Pro)含量、可溶性蛋白(SP)含量、可溶性糖(SS)含量,丙二醛(MDA)含量、质膜相对透性、活性氧(H2O2、OH·和O2•-)含量,抗氧化酶(SOD、POD和CAT)活性、还原型抗坏血酸(AsA)和还原型谷胱甘肽(GSH)含量的影响。并用逐步回归分析建立最优回归方程,进而筛选出不同胁迫程度下对不同抗旱性苜蓿品种抗旱性影响较为显著的指标。【结果】干旱胁迫会显著影响苜蓿的根系生长特征及生理特性。随着干旱胁迫的加剧,供试苜蓿的根系总长度、Pro含量、MDA含量、质膜相对透性、活性氧(H2O2、OH·和O2•-)含量及CAT活性不断增加;根系干重、根系活力、SS含量和GSH含量先增加后下降。此外,随胁迫程度增加,陇中苜蓿的根系平均直径、根体积、根尖数、POD活性及SOD活性均呈先增加后下降的变化趋势,AsA含量不断增加;陇东苜蓿和甘农3号的根系平均直径、根体积、根尖数、POD活性及根系总表面积则呈不断下降的趋势,而AsA含量呈先增加后下降的变化趋势。整体而言,陇中苜蓿的根系总长度、根系总表面积、根系干重显著高于陇东苜蓿和甘农3号,H2O2含量和O2•-含量显著低于甘农3号;陇中苜蓿和陇东苜蓿的SP含量、SS含量和MDA含量显著低于甘农3号。-1.2 MPa至-2.0 MPa胁迫时,陇中苜蓿的H2O2和OH·含量显著低于陇东苜蓿。-2.0 MPa胁迫时,陇中苜蓿的POD活性、AsA和GSH含量均显著高于甘农3号。逐步回归分析表明,根系活力、根体积、根系总长度、MDA和AsA是对陇中苜蓿抗旱性影响较为显著的指标;根尖数、根系平均直径、根系总表面积、根系干重、O2•-、GSH和CAT是对陇东苜蓿抗旱性影响较为显著的指标;根系活力、根尖数、Pro、SS、MDA、质膜相对透性和GSH是对甘农3号紫花苜蓿抗旱性影响较为显著的指标。【结论】不同抗旱性苜蓿品种在形态特征和生理特性上对干旱胁迫存在相同和不同的生长及生理响应策略。轻度和中度胁迫(0 MPa至-1.2 MPa)下,抗旱苜蓿品种主要通过增加根系总长度、根体积和根尖数及降低膜脂过氧化程度来适应干旱,弱抗旱苜蓿品种则通过改变细胞膜稳定性、根系活力及渗透调节能力来适应干旱;重度胁迫(-1.2 MPa至-2.0 MPa)下,不同抗旱性苜蓿品种均可通过改变根系生长特征和启动抗氧化系统来抵御干旱,其中强抗旱苜蓿品种主要通过增加根长和AsA含量来适应干旱,而中等抗旱和弱抗旱苜蓿品种主要通过增加根尖数和GSH含量来适应干旱。

关键词: 苜蓿, 根系, PEG 胁迫, 根系特征, 生理特性, 差异化响应策略

Abstract: 【Objective】This study aimed to understand the differential growth and physiological response in roots of different drought-tolerant alfalfa varieties to drought stress, and to provide theoretical basis for further clarifying the molecular mechanism of alfalfa against drought and for improving drought tolerance and water use efficiency in alfalfa.【Method】In a sand culture experiment, three different drought-tolerant alfalfa varieties, including Medicago sativa L. cv. Longzhong (strong drought-tolerant), Medicago sativa L. cv. Longdong (moderate drought-tolerant), and Medicago sativa L. cv. Gannong No.3 (drought-susceptible), were treated with drought stress induced by polyethylene glycol-6000 (PEG-6000) solutions of different osmotic potentials (0.0, -0.4, -0.8, -1.2, -1.6 and -2.0 MPa). The root growth characters of total root length, total root surface area, average root diameter, root volume, root tip number and root dry weight, root activity, the contents of free proline, soluble protein, and soluble sugar, relative permeability of plasma (RPP), the levels of malondialdehyde (MDA) and reactive oxygen species (ROS), the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT), and reduced ascobate (AsA) and reduced glutathione (GSH) contents were measured at seedling stage. Moreover, stepwise regression analysis was used to establish the optimal regression equation that could select the influential indices for drought-tolerance of the alfalfa varieties under different drought stress levels.【Result】Drought stress has an obvious effect on growth and physiological traits of the alfalfa varieties. With increasing drought stress, the free proline contents, the levels of MDA, RPP and ROS (H2O2, OH· and O2•-), and CAT activity in roots of three alfalfa varieties were significantly increased, while root dry weight, root activity, and the contents of soluble sugar and GSH were firstly increased and then decreased. Additionally, as the osmotic potentials of solutions decreased, average root diameter, root volume, root tip number, POD and SOD activities of Longzhong increased first and then decreased, whereas the above first four indicators and total root surface area of Longdong and Gannong No.3 decreased continuously. Moreover, with the increase of stress, the AsA content of Longzhong continuously increased but that of the other two varieties increased first and then decreased. Overall, total root length, total root surface area and root dry weight in roots of Longzhong were significantly greater than those of Longdong and Gannong No.3, while the H2O2 and OH· levels in roots of Longzhong were significantly lower than those of Gannong No.3. The contents of soluble protein, soluble sugar and MDA in roots of Longzhong and Longdong were obviously lower than those of Gannong No.3. Under the drought stress from -1.2 to -2.0 MPa, the H2O2 and OH· contents in roots of Longzhong were significantly lower than those of Longdong. Under -2.0 MPa, the AsA and GSH contents and POD activity in roots of Longzhong were significantly higher than those of Gannong No.3. The result of stepwise regression analysis showed that root activity, root volume, total root length, MDA and AsA were the most influential indices for drought-tolerance of Longzhong; Root tip number, average root diameter, total root surface area, root dry weight, O2•-, GSH and CAT were the most influential indices for drought-tolerance of Longdong; and root activity, root tip number, free proline, soluble sugar, MDA, RPP and GSH were the most influential indices for drought-tolerance of Gannong No.3.【Conclusion】The alfalfa varieties with different drought-tolerance exhibit common and divergent responses to drought stress at the morphological and physiological levels. Under light and mild drought stress conditions (osmotic potentials decreased from 0 MPa to -1.2 MPa), drought-tolerant alfalfa varieties mainly adapted to drought by increasing the root length, root volume and root tip number and reducing the degree of membrane lipid peroxidation, while drought-susceptible alfalfa varieties adapted to drought by changing cell membrane stability, root activity and osmotic adjustment. Under severe drought stress (osmotic potentials declined from -1.2 MPa to -2.0 MPa), the alteration of root growth and activation of antioxidant system were common response mechanisms of tested alfalfa varieties. Furthermore, strong drought-tolerant alfalfa variety increased total root length and AsA content against drought stress, while moderate drought-tolerant and drought-susceptible alfalfa varieties increased root tip number and GSH content in response to drought stress.

Key words: alfalfa (Medicago sativa L.), root system, PEG stress, root characteristics, physiological traits, differentiated response strategy