紫花苜蓿形态和生理指标响应干旱胁迫的品种特异性

Variety specificity of alfalfa morphological and physiological characteristics in response to drought stress

为研究紫花苜蓿在叶片和根系水平上响应干旱胁迫的形态和生理的品种特异性规律,在温室内分析了干旱胁迫下WL363HQ和巨能7紫花苜蓿株高、分枝数、生物量及叶片和根系中丙二醛(MDA)、脯氨酸、抗氧化酶类物质、C、N含量、C/N、稳定性C同位素(δ^(13)C)和稳定性N同位素(δ^(15)N)。结果表明:干旱胁迫显著降低了供试品种地上部分和根系的干重及分枝数(P<0.05)。干旱胁迫显著降低了巨能7的株高(P<0.05),但增加了巨能7的根冠比,而WL363HQ的结果与之相反,这说明干旱胁迫下供试品种的株高和根冠比具有品种特异性的规律。干旱胁迫增加了WL363HQ和巨能7叶片和根系中MDA和脯氨酸的含量及抗氧化酶物质的活性,且在器官水平也具有品种特异性规律。干旱胁迫下巨能7叶片的MDA含量显著增加(P<0.05),而在WL363HQ根系中的MDA含量也显著增加(P<0.05)。干旱胁迫下WL363HQ叶片脯氨酸含量、POD和SOD活性,及根系SOD的活性均显著增加(P<0.05),而巨能7仅叶片SOD活性,根系脯氨酸含量、POD活性显著升高(P<0.05)。尽管干旱胁迫对供试品种叶片和根系C、N含量无显著影响(P>0.05),但干旱胁迫显著提高了WL363HQ和巨能7紫花苜蓿根系的δ^(13)C(P<0.05),且WL363HQ叶片的δ^(15)N均显著高于巨能7(P<0.05)。此外,干旱胁迫均显著提高了巨能7叶片和根系的C/N(P<0.05)。干旱胁迫下供试品种C、N代谢参数并没有在叶片和根系中表现出较为明显的品种特异性规律,深层次的机制还有待进一步研究。本研究结果将为进一步掌握紫花苜蓿叶片和根系协同抗旱机制及抗旱丰产紫花苜蓿新品种的选育提供理论依据。

This research studied the variety specific morphological and physiological traits of leaves and roots of two different alfalfa cultivars,WL363HQ and MagnumⅦ,under drought in the greenhouse.Measurements made included plant height,branch number and biomass;leaf and root malondialdehyde(MDA)and proline concentration,antioxidant enzyme activities,C and N contents,C∶N ratio,δ^(13)C,andδ^(15)N.Drought stress significantly reduced the dry weight of the above-ground and root,branch number of the tested varieties(P<0.05).Drought stress significantly reduced the plant height of MagnumⅦ(P<0.05),but increased the root-to-shoot ratio;while the opposite result was observed for WL363HQ,indicating that plant height and root-to-shoot ratio of the tested varieties were variety specific traits under drought stress.Drought stress increased the concentrations of MDA and proline,and the activity of antioxidant enzymes in leaves and roots of both WL363HQ and Magnum Ⅶ,and again there were variety specific responses at the organ level.The MDA content of the leaf of MagnumⅦincreased significantly under drought stress(P<0.05),while in WL363HQ MDA levels of roots were significantly increased(P<0.05).Leaf proline content,peroxidase(POD)and superoxide dismutase(SOD)activities,and root SOD activity of WL363HQ were significantly increased under drought stress(P<0.05),while leaf SOD activity,and root proline content,and root POD activity of Magnum Ⅶ were increased significantly(P<0.05).Although drought stress had no significant effect on the C and N concentrations of the leaf and root of the tested varieties(P>0.05),drought stress significantly increased theδ^(13)C of roots of WL363HQ and Magnum Ⅶ(P<0.05),while theδ^(15)N values of leaves of WL363HQ were significantly higher than those of Magnum Ⅶ(P<0.05).Also,drought stress significantly increased the C∶N ratio of the leaves and roots of MagnumⅦ(P<0.05).The metabolic parameters for C and N of the tested varieties under drought stress did not show obvious variety specific differences at the leaf and root level,and the underlying mechanism explaining the observed results needs to be further explored.The results will provide a theoretical basis for further understanding of the integrated drought resistance mechanisms of alfalfa leaves and roots,relevant to the breeding of new drought-resistant and high-yielding alfalfa varieties.