菌根真菌对典型草原植物氮吸收的贡献
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摘要
氮素(N)是陆地生态系统中最重要、最易匮乏的养分之一,是植物个体生长、群落稳定性与生态系统生产力的关键限制因子。作为地球上分布最广泛的共生微生物类群之一,丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)在改善土壤养分和促进植物生长方面有着重要的作用,但AMF能否促进植物对N的吸收?是否受土壤中N水平的影响?对同一群落中不同植物种类N吸收的贡献是否有差异?这些关于AMF生态功能的基本问题还没有得到系统回答。我国是草地资源大国,草地面积占国土总面积的41.7%,但对以AMF为代表的土壤微生物在草地N循环中作用和机理的研究依然匮乏。本研究以内蒙古温带典型草原建群植物羊草(Leymus chinensis)、糙隐子草(Cleistogenes squarrosa)和大针茅(Stipa grandis)为对象,利用分室隔网装置,通过N-15同位素标记不同形态的N(NO3-、NH4+、甘氨酸),研究不同施N水平下AMF对三种不同植物不同形式N吸收的贡献。结果表明,AMF能够帮助植物吸收不同形态的N,对NO3-、NH4+、甘氨酸的吸收能力没有显著差异。AMF吸收和传递N的能力因宿主植物和施N水平的不同而表现出差异,其中糙隐子草的N吸收更多依赖于AMF,这种依赖性在高N环境下尤为明显。在中N水平和高N水平下,羊草根际AMF对于NO3-的吸收能力显著高于糙隐子草和大针茅。土壤中N含量越高,AMF对植物N吸收的贡献越大。这些结果有助于深入理解AMF在改善草地土壤养分和促进植物生长方面的生态学规律,有助于进一步揭示AMF对草地生产力及稳定性的调控机理。
引文
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Veresoglou,S.D.,B.D.Chen,and M.C.Rillig,Arbuscular mycorrhiza and soil nitrogen cycling.Soil Biology&Biochemistry,2012.46:p.53-62.
Barrett,G.,C.D.Campbell,and A.Hodge,The direct response of the external mycelium of arbuscular mycorrhizal fungi to temperature and the implications for nutrient transfer.Soil Biology&Biochemistry,2014.78:p.109-117.
Hodge,A.and A.H.Fitter,Substantial nitrogen acquisition by arbuscular mycorrhizal fungi from organic material has implications for N cycling.Proceedings of the National Academy of Sciences of the United States of America,2010.107(31):p.13754-13759.
Govindarajulu,M.,et al.,Nitrogen transfer in the arbuscular mycorrhizal symbiosis.Nature,2005.435(7043):p.819-823.
Ngwene,B.,E.Gabriel,and E.George,Influence of different mineral nitrogen sources(NO3--N vs.NH4+-N)on arbuscular mycorrhiza development and N transfer in a Glomus intraradices-cowpea symbiosis.Mycorrhiza,2013.23(2):p.107-117.
Veresoglou,S.D.,B.D.Chen,and M.C.Rillig,Arbuscular mycorrhiza and soil nitrogen cycling.Soil Biology&Biochemistry,2012.46:p.53-62.