干旱胁迫条件下AMF促进小马鞍羊蹄甲幼苗生长的机理研究

Arbuscular mycorrhizal fungi(AMF) promotes Bauhinia faberi var.microphylla seedling growth under drought stress conditions

采用温室水分控制试验,在干旱胁迫条件下,定量化研究优势丛枝菌根真菌(AMF)影响优势乡土植物小马鞍羊蹄甲(Bauhinia faberi var.microphylla)幼苗生长的机理,主要通过研究干旱胁迫条件下摩西球囊霉菌(Funneliformis mosseae)与小马鞍羊蹄甲的共生关系,阐明AMF在植物生长初期的作用。结果表明,干旱胁迫条件下,摩西球囊霉菌能够很好地侵染幼苗,侵染率高达89%—97%,并且不受水分条件影响。接种的幼苗最大光合速率、水分利用效率随着干旱胁迫程度从重度到轻度(水分从低到高)逐渐增大,相反地,叶片脯氨酸含量逐渐减小。接种显著地促进幼苗株高、叶片数、叶面积、根长、根面积等生长指标,提高幼苗各部分生物量、地上地下磷(P)含量。当含水量为60%田间持水量时,AMF促进小马鞍羊蹄甲幼苗吸收P的效果最好。接种还显著影响幼苗的生物量分配,在重度干旱胁迫时影响P分配,水分条件也显著影响幼苗的生物量分配。此外,接种和水分的交互作用对叶生物量、总生物量、生长指标以及地上部氮(N)总量影响显著。结果表明干旱胁迫条件下菌根效应显著,并在干旱条件下显著促进了小马鞍羊蹄甲幼苗的生长,这为进一步干旱河谷植被恢复提供了理论依据。

Arbuscular mycorrhizal fungi（AMF） is an important and common type of mycorrhizal fungi,which is widely distributed in soils worldwide.AMF can develop a symbiotic relationship with the roots of most terrestrial plants and can improve the resistance of host plants to drought when under drought stress conditions.Based on our previous studies,we found that AMF had positive roles on the vegetation restoration of native plants in the arid valley of Minjiang River,and its role was even more significant in the driest core area of the dry valley.However,the underlying mechanisms of how AMF affects the growth of its native host plant under drought stress conditions remains unclear.To investigate the effects of AMF on its native plant,we designed a full factorial and completely random pot experiment in a greenhouse.We attempted to quantitatively clarify the roles of AMF in the seedlings by testing the symbiotic relationship between Bauhinia faberi var.microphylla seedlings（B.faberi） and one dominant arbuscular mycorrhizal fungi（Funneliformis mosseae,FM） under three drought stress conditions.Continuous drought was induced by watering seedlings at one-day intervals with distilled water over four months with three water content levels.These were low,middle,and high,represented,respectively,by 40%,60%,and 80% of the field capacity.At the end of the experiment,we measured the maximum photosynthetic rate,proline content,biomass production and carbon partitioning,nutrient content,inoculation rate,and mycorrhizal growth response（MGR） before the seedlings were harvested.One-and two-way ANOVA were used for statistical analysis.The results showed that FM could colonize the roots of B.faberi seedlings well,with the average proportion of mycorrhizal colonization being as high as 89% —97% under drought stress conditions.The maximum photosynthetic rate and water use efficiency of the inoculated seedlings were enhanced as the soil water content increased from low to medium and high levels.However,the proline content in leaves decreased.Inoculation of FM can significantly promote an increase in the height,leaf number,leaf area,root length,root area,and biomass of seedlings,and P concentration both in shoots and in roots,which indicated that FM could benefit the growth of its host plant.Specifically,B.faberi seedlings had the highest P concentration under the medium water treatment（60% field capacity） compared to the other treatments.Moreover,inoculation significantly affected the biomass allocation of seedlings to the shoot and root and affected P allocation of seedlings when under the most severe drought stress.R/S of mycorrhizal seedlings was significantly higher than that of non-mycorrhizal seedlings under the same water stress conditions.R/S of mycorrhizal seedlings was significantly higher under the low water treatment,which means that seedlings allocated more carbohydrates to the root than to the shoot.Moreover,the interaction between AMF and soil water condition significantly affected leaf biomass,total biomass,and shoot-N content.We found that the mycorrhizal growth response of FM was remarkable and that FM significantly promoted the growth of B.faberi seedlings under drought stress conditions,which provides a theoretical basis for arid valley vegetation restoration practice.