干旱胁迫对不同根型苜蓿根系生理特性及解剖结构的影响

Influences of drought stress on physiological charac⁃ teristics and anatomical structure of alfalfa roots of different root-types

摘要:

【目的】揭示不同根型苜蓿幼苗根系对干旱胁迫的响应和调控机制。【方法】采用沙培盆栽法，以根茎型清水紫花苜蓿、直根型陇东紫花苜蓿、根蘖型公农 4 号杂花苜蓿为试验材料，设置对照 （CK）、中度（M）和重度（S）3 种干旱处理，研究干旱胁迫对不同根型苜蓿根系生理特性和解剖结构的影响。【结果】随干旱胁迫加剧，各根型苜蓿根系可溶性蛋白、可溶性糖、脯氨酸和 MDA 含量及 SOD、 POD、CAT 活性绝大部分显著升高，其中清水紫花苜蓿根系 MDA 含量增幅相对较小，这与增加渗透调节物质（脯氨酸、可溶性糖、可溶性蛋白）和抗氧化保护酶系统（POD、SOD、CAT）有关，且各根型苜蓿幼苗期对脯氨酸、可溶性糖、POD 和 SOD 的响应更敏感；各根型苜蓿根系木质部面积、韧皮部面积、木质部导管数量、导管面积、导管直径均随干旱胁迫程度加剧显著增加，而皮层厚度大多显著减小。 【结论】各根型苜蓿幼苗期根系通过对渗透调节物质、抗氧化保护酶和根系内部解剖结构的调节来维持自身的正常生理代谢功能，抵抗一定的水分亏缺。

Abstract:

【Objective】 In order to reveal the response and regulation mechanism of the root of alfalfa seedlings with different root types to drought stress.【Method】 Three root types of alfalfa （rhizomatous rooted Medicago sativa ‘Qingshui’，tap rooted M. sativa‘Longdong’，creeping rooted M. Varia Martin ‘Gongnong No. 4’） were cultured in river sand with nutrient solution，control （CK），moderate （M），and severe （S）drought treatments were set up to study the effects of drought stress on root physiological characteristics and anatomical structure.【Result】 The con- tents of soluble protein，soluble sugar，proline and MDA，as well as the activities of SOD，POD and CAT increased significantly in most root types of alfalfa under drought stress. The increase of MDA content of Qingshui was rela- tively small，which was related to the increase of osmotic adjustment substance （proline，soluble sugar andsoluble pro- tein） and antioxidant protective enzyme system （POD，SOD，and CAT activities）. The responses of proline and soluble sugar contents，POD and SOD activities were more sensitive in the root of seedling stage. The xylem area， phloem area，xylem vessel number，vessel area，and vessel diameter increased significantly with the increase of drought stress，while the cortex thickness decreased significantly.【Conclusion】 The root systems of alfalfa seedlings with different root types maintained their normal physiological and metabolic functions and resisted drought stress by regulating osmotic regulators，antioxidant protective enzymes and internal anatomical structure of root during seedling stage.