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

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

采用盆栽试验研究在3个镉污染(0,6和12mg 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(0mg 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12mg Cd/kg条件下降低了33.90%、19.17%和31.95%;0mg 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12mg 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12mg 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(NH_4^+-N)和硝态氮(NO_3^--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6mg Cd/kg时,接种Gt菌种不利于紫花苜蓿的生长。

A pot experiment in a greenhouse was conducted to investigate the growth and nitrogen（N）uptake of Medicago sativainoculated 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 NH_4~＋-N and NO_3^--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 6mg Cd/kg.