Hg、Cd污染对2种外生菌根真菌氮素营养吸收的影响

摘要

以从中国西南林区分离获得的外生菌根真菌彩色豆马勃(Pisolithus tinctorius 715,简称Pt715)、松乳菇(Lactarius delicious.ex Gray-1(简称Ld-1)、Lactarius delicious.ex Pink-2(简称Ld-2)、Lactarius delicious.ex White-3(简称Ld-3))为供试菌种,研究Hg、Cd对其吸收氮素的影响,从而筛选出在营养吸收上具有重金属耐受性的菌株.结果表明,重金属对外生菌根真菌吸收氮素营养的影响因重金属元素种类、真菌种类和氮素形态不同而异,Hg、Cd基本不会抑制供试菌种对有机态氮的吸收,而对NH4+-N、NO3--N的吸收有不同程度的抑制或促进作用,但无明显的规律可循；Ld-1菌株具有一定的耐Hg性,在培养液中加入不同浓度的Hg后,Ld-1菌株对3种氮源的吸收均未受到明显抑制,相反在高Hg浓度下还促进了对NH4+-N、NO3--N的吸收.Ld-1菌株有可能在Hg的胁迫下诱导合成了新的特异性蛋白,Hg与特异性蛋白结合从而缓解了其污染胁迫.%Four ectomycorrhizal fungal strains of Pisolithus tinctorius 715 (Pt715 for short),Lactarius delicious.ex Gray-1 (Ld-1 for short),Lactarius delicious.ex Pink-2 (Ld-2 for short) and Lactarius delicious.ex White-3 (Ld-3 for short) were isolated from laterite of southwest forestry area.Batch experiments were carried out to investigate the effect of Hg and Cd stress on nitrogen absorption of ectomycorrhizal fungi so as to screening out the strains that tolerance to heavy metals at nutrient adsorption.Results showed that the nutrient adsorption of ectomycorrhizal fungi could be influenced by the type of heavy metal,species of ectomycorrhizal fungi and form of nitrogen.No obvious changes were observed in organic nitrogen accumulation by ectomycorrhizal fungi grown in mediums with and without Hg and Cd,whilst the accumulation of nitrogen was obviously restrained or enhanced by Hg and Cd.Ld-1 presented perfect tolerance to Hg,when cultured in medium with different concentration of Hg,the nitrogen accumulation of Ld1 was not resistant,conversely,the adsorption NH4+-N,NO3--N even promoted under high concentration of Hg stress.Hg stress might induce Ld-1 to synthesis a new specific protein,which played a key role in alleviating the Hg stress.