Mycorrhizal symbiosis changes host nitrogen source use

Tiina Savolainen,Minna-Maarit Kytöviita

doi:10.1007/s11104-021-05257-5

Abstract

PurposeThe ecological importance of arbuscular mycorrhizal fungi (AMF) in plant acquisition of inorganic and organic sources of nitrogen (N) is not clear. To improve understanding of the plant N nutrition ecology, we tested the effect of intraspecific competition and AMF in plant N source use in growth and N acquisition.MethodsSolidago virgaurea was grown in microcosms in a fully factorial experiment under greenhouse conditions. The factors tested were intraspecific competition between seedlings and adult plants (yes, no), N source (NH4, glycine) and AMF (inoculated with Glomus hoi, not inoculated).ResultsWhen grown separately, non-mycorrhizal seedling growth was highest when grown with ammonium, but non-mycorrhizal adults grew best with glycine as the sole N source. Mycorrhizal symbiosis with Glomus hoi evened out this initial niche partitioning in terms of differences in N source use and all mycorrhizal plants grew best with ammonium. Competition shaped plant benefit from mycorrhizal symbiosis depending on the N source. Competition reduced mycorrhizal growth benefit in glycine-grown seedlings, but not in adults. Plant performance did not show uniform relationship with δ15N, but δ15N was affected by life stage, competition and mycorrhiza.ConclusionsPlant competition and AMF shape plant N source use. Plant and AMF benefit of the symbiosis depend on the N source.

Highlights

In plant communities, access to multiple nitrogen (N) sources may enhance plant performance and alter ecological interactions in ways that may promote coexistence
Niche partitioning of resources due to interspecific differences in structural and physiological traits have been considered to explain the coexistence of many species in plant communities (Levine and HilleRisLambers 2009; Silvertown 2004)
Despite differences in N source use when nonmycorrhizal, both adults and seedlings of mycorrhizal Solidago virgaurea performed when supplied with NH4 as the N source

Summary

Introduction

Access to multiple nitrogen (N) sources may enhance plant performance and alter ecological interactions in ways that may promote coexistence. The soil N in the Arctic, alpine tundra and boreal forests can be predominantly in organic form (Kielland 1994, 1995; Lipson et al 1999; Näsholm et al 1998; Stark and Kytöviita 2006) In these strongly N limited ecosystems, plants can take up dissolved organic N directly from the soil in the form of amino acids, thereby circumventing part of the N mineralization process (Chapin et al 1993; Kielland 1994; Nordin et al 2004). Mycorrhizal symbiosis has an essential role in plant nutrition and ecosystem dynamics, exactly how mycorrhizas affect plant N acquisition, use and competition for N is not fully understood

Methods

Results

Conclusion