[目的]不同Al3+水平下,研究马尾松菌根/非菌根幼苗的生理、根尖细胞超微结构的变化以及Al的亚细胞分布,分析菌根化苗木对铝的响应及其耐铝性,为外生菌根真菌提高寄主植物耐铝性和育苗造林应用提供理论依据.[方法]以半年生菌根和非菌根马尾松苗为材料,采用砂培盆栽浇铝法,分别设置 0、0.2、0.4、0.8 mmol·L-1 Al3+(AlCl3)处理,分析其根系抗氧化酶活性和MDA含量等生理指标变化,Al的亚细胞分布,通过组织染色观察根尖ROS和MDA分布,并观察根尖超微结构变化.[结果](1)随外源[Al3+]的升高,马尾松菌根/非菌根苗根系SOD、CAT、POD活性和MDA含量均呈总体上升趋势,在高铝(0.8 mmol·L-1)水平时,抗氧化酶活性和MDA含量最大,且非菌根苗受到铝的影响程度更大;(2)随外源[Al3+]的升高,马尾松根尖吸收的铝含量显著增加,且菌根苗吸收的铝含量显著高于非菌根苗;(3)从细胞超微结构和Al的亚细胞分布看,大量Al3+首先与细胞壁结合,细胞内的Al3+与生物膜强烈结合,使细胞器物质向外渗漏作用加强,干扰细胞核和线粒体等的各种调节过程.而由于菌根对铝的吸附作用,降低了侵入细胞内的铝离子含量,保护亚细胞器结构的同时也维持了细胞的基本功能,从而缓解铝毒性.[结论]铝处理使马尾松根系抗氧化酶活性和MDA含量增加,0.4 mmol·L-1 以上的铝浓度产生明显铝毒害症状.而菌根可以通过吸收更多的铝降低铝毒害,并提高植物耐铝能力,这很可能是马尾松菌根苗的一个重要外部抗性机制.
[Objective]To provide theoretical basis for the application of ectomycorrhizal fungi in improving the aluminum tolerance of host plants and afforestation,we studied the changes of physiology,root tip cell ultrastructure and subcellular distribution of Al in mycorrhizal/non mycorrhizal seedlings of Pinus massoni-ana under different Al3+ levels.[Method]Semi annual mycorrhizal and non mycorrhizal P.massoniana seedlings were treated with 0,0.2,0.4 and 0.8 mmol·L-1 Al3+(AlCl3)respectively by sand culture and pot ir-rigation with aluminum.We analyzed the changes of antioxidant enzyme activity,MDA content and subcel-lular distribution of Al in roots,the distribution of ROS and MDA in roots,and the ultrastructure of root tips.[Results](1)With the increase of exogenous aluminum concentration,the activities of SOD,CAT,POD and the content of MDA in the roots of mycorrhizal/non mycorrhizal seedlings of masson pine showed an overall upward trend.At high aluminum level(0.8 mmol·L-1),the activities of antioxidant enzymes and the content of MDA were the highest,and the non mycorrhizal seedlings were more affected by aluminum.(2)With the increase of exogenous aluminum concentration,the aluminum content absorbed by root tips of P.massoniana increased significantly,and the aluminum content absorbed by mycorrhizal seedlings was sig-nificantly higher than that of non mycorrhizal seedlings.(3)From the cell ultrastructure and subcellular dis-tribution of Al,a large number of Al3+ first combined with the cell wall,and the intracellular Al3+ strongly combined with the biofilm,which strengthened the leakage of organelles and interfered with various regu-latory processes of nucleus and mitochondria.Because of the adsorption of aluminum by mycorrhiza,the content of aluminum ions in cells reduced,the structure of subcellular organelles was protected,the basic function of cells was maintained,and the toxicity of aluminum was alleviated.[Conclusion]The antioxid-ant enzyme activity and MDA content of root of P.massoniana are increased by aluminum treatment,and aluminum with 0.4 mmol·L-1 produces obvious aluminum toxicity symptoms.Mycorrhizal fungi can reduce aluminum toxicity and improve plant aluminum tolerance by absorbing more aluminum,which is probably an important external resistance mechanism of root seedlings mycorrhiza of P.massoniana.