干旱条件下AM真菌对植物生长和土壤水稳定性团聚体的影响

采用分室培养系统,模拟正常水分和干旱胁迫两种环境条件,探讨不同丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)对紫花苜蓿(Medicago sativa L.)生长和土壤水稳性团聚体的影响.试验条件下,Glomus intraradices对苜蓿根系的侵染率均显著高于Acaulospora scrobiculata和Diversispora spurcum接种处理.正常水分条件下,供试AM真菌均能显著提高植株生物量及磷浓度.干旱胁迫显著抑制了植株生长和菌根共生体发育,总体上菌根共生体对植株生长没有明显影响,接种D.spurcum甚至趋于降低植株生物量；同时,仅有G.intraradices显著提高了植株磷浓度.AM真菌主要影响到＞2mm的水稳性团聚体数量,以G.intraradices作用效果最为显著.在菌丝室中,G.intraradices显著提高了总球囊霉素含量.研究表明AM真菌对土壤大团聚体形成具有积极作用,而菌根效应因土壤水分条件和不同菌种而异,干旱胁迫下仅有G.intraradices对土壤结构和植物生长表现出显著积极作用.在应用菌根技术治理退化土壤时,需要选用抗逆性强共生效率高的菌株,对于不同AM真菌抗逆性差异的生物学与遗传学基础尚需进一步研究.

Influences of AM fungi on plant growth and water-stable soil aggregates under drought stresses

In the present study the influences of different arbuscular mycorrhizal (AM) fungal species on the formation of water-stable soil aggregates and growth of Medicago sativa L. were examined under simulated drought stresses in a compartmented cultivation system. In addition to observations on mycorrhizal colonization, plant growth responses and soil aggregates, we also monitored soil chemo-physical properties and plant physiological responses for uncovering the mechanisms underlying mycorrhizal functions. The experimental results indicated that, root colonization by Glomus intraradices was significantly higher than those by the other two fungal species, Acaulospora scrobiculata and Diversispora spurcum irrespective to soil water conditions. Under well watered conditions, all three AM fungal species significantly increased plant biomass and P concentrations; while drought stresses significantly inhibited plant growth and mycorrhizal colonization. There were no observable mycorrhizal effects on plant growth under drought stresses, meanwhile, inoculation with D. spurcum even reduced plant biomes, and only G. intraradices increased plant P concentrations. As for mycorrhizal effects on soil structure, AM fungi mainly affected water stable soil aggregates with particle size > 2 mm, and G. intraradices exhibited most prominent effects. Consistently, G. intraradices significantly increased the contents of glomalin-related soil proteins in the hyphal compartment of the cultivation system. The study clearly demonstrated the positive influences of AM fungi on formation of large soil aggregates and plant drought tolerance, while there was large variation among different AM fungal species. To make sure of successful ecological restoration of degraded ecosystem with assistance of mycorrhizal fungi, selection of tolerant AM fungal strains should be fully considered. At present, further study is still necessary to reveal the biological and molecular basis for the differences in stress tolerance of different AM fungal species.