Uptake of organic nitrogen by plants

• Published in: The New phytologist Vol. 182; no. 1; pp. 31 - 48
• Main Authors: Näsholm, Torgny, Kielland, Knut, Ganeteg, Ulrika
• Format: Journal Article
• Language: English
• Published: Oxford, UK Oxford, UK : Blackwell Publishing Ltd 01.04.2009; Blackwell Publishing; Blackwell Publishing Ltd
• Subjects: Acid soils; amino acid composition; amino acid metabolism; Amino acid transport systems; amino acid transporters; Amino acids; Amino Acids - metabolism; competition; dissolved organic nitrogen (DON); Forest Science; Forest soils; Membrane Transport Proteins - metabolism; mycorrhizal fungi; Nitrogen; Nitrogen - metabolism; nitrogen cycling; nutrition research; Organic Chemicals - metabolism; Organic foods; Organic soils; plant nutrition; Plant roots; Plants; Plants - metabolism; Skogsvetenskap; Soil; Soil ecology; Transley Reviews
• ISSN: 0028-646X; 1469-8137; 1469-8137
• DOI: 10.1111/j.1469-8137.2008.02751.x

Summary 31 I. Introduction 31 II. Availability 32 III. Uptake 34 IV. Field studies of plant amino acid uptake 41 V. Conclusions and future perspectives 43 Acknowledgements 44 References 45 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.