Abstract: To investigate the mitigating effects of exogenous triacontanol （TA） application on the growth of alfalfa （Medicago sativa） seedlings under drought stress， a sand culture method with nutrient solution was used. Drought-resistant new lines （P1， P2） and drought-sensitive materials （7809， 15578） were subjected to the following treatments： control （CK）， drought stress （-1.6 MPa PEG-6000， T₁）， and drought stress combined with foliar sprays of TA at 3， 6， 9， and 12 μmol·L^-1 （denoted as T₂， T₃， T₄， and T₅， respectively）. Morphological， physiological， and photosynthetic parameters were measured to analyze the impact of different TA concentrations. The results indicated that all TA concentrations significantly alleviated drought stress by enhancing plant height， leaf area， root activity， above-ground biomass， below-ground biomass， and photosynthetic parameters， while significantly reducing contents of soluble sugar， soluble protein， proline， malondialdehyde， and superoxide anion. Membership function analysis ranked the mitigation efficacy of TA treatments as T₃>T₄>T₂>T₅>T₁， and among materials as 15578>P1>7809>P2， demonstrating a greater alleviative effect on sensitive materials in general. These findings provide practical guidance for the scientific application of TA in drought-tolerant alfalfa cultivation.

Key words: Alfalfa, Drought stress, Triacontanol, Photosynthetic physiology

摘要： 为探究干旱胁迫下外施三十烷醇（Triacontanol，TA）对紫花苜蓿（Medicago sativa）幼苗生长的缓解效应，本研究采用营养液砂培法，以抗旱新品系（P1、P2）和干旱敏感性材料（7809、15578）为研究对象，设置对照（CK）、干旱胁迫（-1.6MPa PEG-6000，T₁）及干旱胁迫下喷施3，6，9，12 μmol·L^-1 TA（分别记为T₂，T₃，T₄，T₅），测定各处理下供试紫花苜蓿的形态、生理及光合指标变化，分析不同浓度TA处理对紫花苜蓿幼苗生理特征的影响。结果表明：外施不同浓度的TA均对紫花苜蓿干旱胁迫有缓解效应，均能显著提高其株高、叶面积、根系活力、地上生物量、地下生物量及光合参数，显著降低可溶性糖、可溶性蛋白、脯氨酸、丙二醛和超氧阴离子含量。隶属函数分析表明，外源TA对紫花苜蓿干旱胁迫缓解能力由高到低的排序为：T₃>T₄>T₂>T₅>T₁，材料间表现为15578>P1>7809>P2，其研究结果为TA在苜蓿耐旱栽培中的科学应用提供了实践指导。

关键词: 紫花苜蓿, 干旱胁迫, 三十烷醇, 光合生理