Uptake of organic nitrogen by plants

Abstract

Contents Summary 31 Introduction 31 Availability 32 Uptake 34 Field studies of plant amino acid uptake 41 Conclusions and future perspectives 43 Acknowledgements 44 References 45 Summary Languishing for many years in the shadow of plant inorganic nitrogen (N) nutrition research, studies of organic N uptake have attracted increased attention during the last decade. The capacity of plants to acquire organic N, demonstrated in laboratory and field settings, has thereby been well established. Even so, the ecological significance of organic N uptake for plant N nutrition is still a matter of discussion. Several lines of evidence suggest that plants growing in various ecosystems may access organic N species. Many soils display amino acid concentrations similar to, or higher than, those of inorganic N, mainly as a result of rapid hydrolysis of soil proteins. Transporters mediating amino acid uptake have been identified both in mycorrhizal fungi and in plant roots. Studies of endogenous metabolism of absorbed amino acids suggest that L‐ but not D‐enantiomers are efficiently utilized. Dual labelled amino acids supplied to soil have provided strong evidence for plant uptake of organic N in the field but have failed to provide information on the quantitative importance of this process. Thus, direct evidence that organic N contributes significantly to plant N nutrition is still lacking. Recent progress in our understanding of the mechanisms underlying plant organic N uptake may open new avenues for the exploration of this subject.

A novel fungal family of oligopeptide transporters identified by functional metatranscriptomics of soil eukaryotes

“…It is however intriguing that this gene family, as several other transporter families (De Hertogh et al, 2006), has a patchy distribution in the fungal kingdom although proteins represent a widespread source of N in the environment and specifically in soils (Jones et al, 2009;Näsholm et al, 2009). Furthermore, presence of the FOT family does not seem to represent a marker of a specific lifestyle in the fungi as the species that harbor it are either saprotrophic (Yarrowia lipolytica, Zygosaccharomyces rouxii, Postia placenta or S. lacrymans), facultative animal pathogens (Ajellomyces capsulatus, Asp.…”

“…Although the two fully sequenced symbiotic ectomycorrhizal species, L. bicolor and T. melanosporum, do not have any FOT genes in their genomes, because of the patchy distribution of this gene family, we cannot exclude that this gene family is present in the genomes of other mycorrhizal species. In this case, the FOT genes could represent one of the component participating in the functioning of the ectomycorrhizal symbiosis known to allow forest trees to indirectly use soil organic N sources (Read and Perez Moreno, 2002;Näsholm et al 2009). …”

Nitrate transporters: an overview in legumes

“…Plants can absorb both organic and inorganic nitrogen forms. However, there is no direct evidence that organic nitrogen contributes significantly to the nitrogen nutrition of the plant (Näsholm et al 2009). Thus, most of the nitrogen taken-up by the plant is in an inorganic form, mainly nitrate (NO 3 -) and ammonium (NH 4 ?…”

Manure and sorbent fertilisers increase on-going nutrient availability relative to conventional fertilisers

“…However, it is known that some organic nutrients are available to plants (Paungfoo-Lonhienne et al, 2008Schmidt et al, 2013). The relative importance of organic nutrient uptake (compared to inorganic nutrient forms) remains unknown (Nasholm et al, 2009).…”