Abstract: To study the effects of aluminum (Al) stress on alfalfa seedling growth and physiolgical and biochemical indexes,we investigated responses of eight alfalfa germplasms in Yunnan on aluminum stress treatments. The results showed that low concentration (≤ 100 μmol·L^-1) of Al treatment had weaker inhabitory effect on the plant growth and root elongation of alfalfa seedlings,but strongly affected root vitality,significantly promoted the accumulation of malondialdehyde (MAD) in the root tips. Due to the self-regulatory mechanism of alfalfa under the stress,the aluminum toxicity could be alleviated. We found when the Al stress treatment was ≥ 200 μmol·L^-1,the root activity decreases and the malondialdehyde accumulation tends to be gentle. With the increase of aluminum concentration,the root tip of the alfalfa was affected by the increase of Al stress,and the activity of oxidase decreased gradually. The Al resistance of 8 tested materials was evaluated by membership function method. They were divided into Al-resistant,medium-Al-resistant and sensitive. The comprehensive analysis showed that Al tolerance of alfalfa (No.12) is the best,and it can be applied in the acid aluminized soil in the the southern acidic aluminizing soil.

Key words: Medicago, Aluminum stress, Root activity, Malondialdehyde, Antioxidant enzyme activity

摘要： 以8份云南苜蓿资源为研究材料，研究了铝胁迫对苜蓿幼苗生长及生理生化指标的影响。结果表明，低浓度（≤100 μmol·L^-1）铝处理对苜蓿幼苗的植株生长及根系伸长的抑制作用较弱，但对苜蓿根系活力抑制作用较大，且促进了丙二醛在根尖的积累，破坏膜系统的通透性；由于在逆境中苜蓿自身调节机制作用缓解铝毒害，当胁迫处理浓度≥200 μmol·L^-1时，根系活力下降及丙二醛积累变化趋势较为平缓。随着铝处理浓度的增加，苜蓿根尖受胁迫影响随之增大，氧化酶活性呈逐级递减的趋势。采用隶属函数法对8份供试苜蓿材料耐铝性进行评价，可将供试材料分为耐铝型、中等耐铝型和敏感型三种，综合分析认为紫花苜蓿（No.12）在不同浓度铝胁迫处理下耐铝性表现均较好，可在南方酸性富铝化土壤中推广应用。

关键词: 苜蓿, 铝胁迫, 根系活力, 丙二醛, 抗氧化酶活性