喀斯特土壤条件下丛枝菌根真菌侵染对任豆幼苗生物量分配和根系结构特征的影响

喀斯特地区土壤瘠薄,植被恢复困难,根系对幼苗生长发育起重要作用。丛枝菌根真菌(AMF)侵染可促进喀斯特植物干物质积累及提升抗逆能力,但AMF对喀斯特地区主要恢复树种根系侵染机制及影响的研究尚不够深入。本研究以喀斯特地区典型造林树种任豆(Zenia insignis)幼苗为试验材料,利用不同养分条件的喀斯特原生土壤开展盆栽试验,以摩西球囊霉(Funneliformis mosseae,Fm)、根内球囊霉(Rhizophagus intraradices,Ri)和2种菌根真菌混合菌剂(mixture inoculation,Mi)进行接种,分析不同养分土壤条件下菌根真菌对任豆幼苗生物量分配和根系结构特征影响。结果表明:贫瘠喀斯特土壤条件下Fm处理根系侵染率最高,地上部生物量、根系生物量、总生物量、根尖数、分叉数、交叉数和投影面积较CK提高2.50、5.60、3.67、3.03、3.78、3.66和3.56倍;Ri处理对地上部生物量、根系生物量、总生物量、分叉数无显著影响,根尖数、交叉数、投影面积较对照降低46.59%、50.00%、38.60%;Mi处理地上部生物量、根系生物量、总生物量、分叉数、交叉数和投影面积较CK提高3.02、3.47、3.14、1.64、1.60和1.70倍,对根尖数无显著影响。较高养分喀斯特土壤条件下Fm处理根系生物量、投影面积较CK提高2.38、1.51倍,对地上部生物量、总生物量、分叉数和交叉数无显著影响,根尖数较CK降低22.82%;Ri处理根系生物量、总生物量、根尖数、交叉数和投影面积较CK提高2.29、1.37、1.31、1.29和1.66倍,对地上部生物量、根系分叉数无显著影响;Mi处理地上部生物量、总生物量、根尖数和投影面积较CK提高1.44、1.46、1.25和1.40倍,对根系生物量、分叉数和交叉数无显著影响。养分较低条件下,Fm侵染有利于任豆生物量提高和吸收性根系分化,有助于根系觅食养分和水分,促进植物生长;养分较高条件下,Ri促进根系结构特征改变,Fm促生效应减弱。低钙高磷养分条件下Ri表现出较强的促生作用;Fm生态适应性强,在促进植物根系获取土壤养分、水分及土壤空间拓展方面具有显著优势,可作为菌根真菌促进喀斯特地区植被恢复的优势菌种。

Effects of arbuscular mycorrhizal fungi on biomass distribution and root architecture characters of Zenia insignis seedlings in karst soil

Vegetation recovery in karst region is limited by poor availability of soil nutrients.Root plays an important role in the growth and development of seedlings.Arbuscular mycorrhizal fungi(AMF)can promote dry matter accumulation and stress resistance of karst plants,whereas the mechanism and effect of AMF infection on roots of main restoration tree species in karst area remain largely unknown.In this study,the effects of AMF on growth,root architecture of Zenia insignis in karst soil with different nutrient levels were evaluated in a greenhouse experiment.There were four inoculations of arbuscular mycorrhizal fungi:Funneliformis mosseae(Fm),Rhizophagus intraradices(Ri),their mixture inoculation(Mi)and no inoculation(CK),and two nutrient levels.Under low-nutrient level,Fm treatment significantly increased root architecture parameters.The inoculated plants had the maximum colonization rate,and aboveground biomass,root biomass,total biomass,the numbers of tips,forks and crossings and projected area were increased by 2.50,5.60,3.67,3.03,3.78,3.66 and 3.56 times than CK,respectively.Ri treatment did not affect aboveground biomass,root biomass,total biomass and the number of forks,but decreased the numbers of tips and crossings and projected area by 46.59%,50.00%,and 38.60%,respectively.Mi treatment increased aboveground biomass,root biomass,total biomass,the numbers of forks and crossings and projected area by 3.02,3.47,3.14,1.64,1.60 and 1.70 times,respectively,but did not affect the number of tips.Under higher-nutrient level,Fm treatment increased root biomass and projected area by 2.38 and 1.51 times respectively,did not affect aboveground biomass,total biomass,the numbers of forks and crossings,but decreased the number of tips by 22.82%.Ri treatment increased root biomass,total biomass,the numbers of tips and crossings and projected area by 2.29,1.37,1.31,1.29 and 1.66 times,but did not affect aboveground biomass and the number of forks.Mi treatment increased aboveground biomass,total biomass,the number of tips and projected area by 1.44,1.46,1.25 and 1.40 times,but did not affect root biomass,the numbers of forks and crossings.Collectively,inoculation with F.mosseae significantly increased root architecture parameters and plant growth under low-nutrient soil.R.intraradices had a positive impact in soils with low calcium and high phosphorus contents.F.mosseae has extensive ecological adaptability and facilitates resource uptake of roots and root spatial expansion in soils,showing high application potential for vegetation restoration under low-nutrient karst soil.