镉污染和接种丛枝菌根真菌对紫花苜蓿生长和氮吸收的影响

采用盆栽试验研究在3个镉污染(0,6和12 mg Cd/kg)水平下,接种5种丛枝菌根真菌[分别接种聚丛球囊 Glomus aggregatum(Ga)、幼套球囊霉 G. etunicatum (Ge)、扭形球囊霉 G. tortuosum(Gt)、根内球囊霉 G. intraradices(Gi)和地表球囊霉 G. versiforme(Gv),以不接种为对照]对紫花苜蓿生长和氮吸收的影响。结果表明:与不加镉(0 mg Cd/kg)处理相比,接种Ga、Gi 和Gt菌种处理的紫花苜蓿菌根侵染率在12 mg Cd/kg条件下降低了33.90%、19.17%和31.95%;0 mg Cd/kg水平下接种Gt菌种紫花苜蓿总生物量分别比接种 Ga、Ge、Gi和Gv菌种处理显著高出33.19%、67.74%、57.29%和34.91%,但在12 mg Cd/kg水平时总生物量与以上菌种处理相比,分别降低16.67%、34.07%、32.96%和52.76%;在镉浓度为12 mg Cd/kg时,接种Gv菌种处理的紫花苜蓿株高、根瘤菌数量、地上生物量、总生物量、地上植株氮含量和整株含氮量与不接种处理相比,分别增加 65.41%、95.24%、61.87%、50.30%、5.83%和71.55%;随镉浓度增加接种Gv菌种处理紫花苜蓿土壤中铵态氮(NH₄⁺-N)和硝态氮(N₃^--N)浓度显著下降。综上分析,在镉污染条件下,接种Gv菌种能促进紫花苜蓿生长和氮吸收;当土壤镉浓度超过6 mg Cd/kg时,接种Gt菌种不利于紫花苜蓿的生长。

Effects of cadmium and arbuscular mycorrhizal fungi inoculation on the growth and nitrogen uptake of alfalfa (Medicago sativa)

A pot experiment in a greenhouse was conducted to investigate the growth and nitrogen (N) uptake of Medicago sativa inoculated with different arbuscular mycorrhizal fungi [Glomus aggregatum (Ga),Glomus etunicatum (Ge),Glomus intraradices (Gi),Glomus tortuosum (Gt),Glomus versiforme (Gv)] or un-inoculated in soil without or with cadmium at two concentrations (6 and 12 mg Cd/kg).Mycorrhizal colonization of alfalfa inoculated with Ga,Gi,and Gt was 33.90％,19.17％,and 31.95％ lower,respectively,in 12 mg Cd/kg soil than in 0 mg Cd/kg soil.In soil without Cd,the biomass of the Gt-inoculated plants was 33.19 ％,64.74％,57.29％,and 34.91％ higher than that in the Ga,Ge,Gi,and Gv treatments,respectively.In 12 mg Cd/kg soil,the biomass of the Gt-inoculated plants was 16.67％,34.07％,32.96％,and 52.76％ lower than that of those inocluated with Ga,Ge,Gi,and Gv,respectively.Compared with uninoculated plants,those inoculated with Gv showed significantly increased shoot height,number of nodules,shoot biomass,total biomass,shoot N content,and total N content (by 65.41％,95.24％,61.87％,50.30％,5.83％,and 71.55％,respectively) in soil containing 12 mg Cd/kg.The NH4+-N and NO3--N concentrations in soil significantly decreased with increasing Cd levels in the Gv-inoculation treatments.These results showed that Gv inoculation promoted the growth and N uptake of alfalfa in Cd-contaminated soils,whereas Gt inoculation could not benefit the growth of alfalfa grown in soils containing more than 6 mg Cd/kg.