| Nitrogen transport in the xylem sap of Quercus ilex: the role of ornithine. | |
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MedLine Citation:
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PMID: 15940878 Owner: NLM Status: MEDLINE |
Abstract/OtherAbstract:
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The storage and remobilization of nitrogen in deciduous and evergreen species is a major source of N, supporting the seasonal growth of trees. In evergreens, in addition to wood and roots, older leaves are important reservoirs of N used in the growth of new foliage. Just before bud burst, when transpiration is inactive or low, and when uptake of nitrogen by the roots may be restricted due to low temperatures, levels of organic N in the xylem are high. Amino acids usually comprise the bulk of this organic N. Changes in amino acid concentrations in early spring are thought to result mainly from hydrolysis of N reserves, and not from current N uptake. The seasonal profiles of amino acids in the xylem sap of Quercus ilex, an evergreen Mediterranean tree, were investigated. The first amino acid detected in the xylem sap before spring was ornithine, which may result from the breakdown of arginine present in storage proteins. Arginine is one of the main amino acids present in storage proteins because each arginine molecule has four nitrogen atoms. When protein degradation increases the free arginine pool, the arginase activity is enhanced and, consequently, the conversion of arginine to ornithine. It seems that ornithine has an important role in N transport early in the growth season of Q. ilex. |
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Authors:
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Cristina Nabais; Jürgen Hagemeyer; Helena Freitas |
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Publication Detail:
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Type: Journal Article; Research Support, Non-U.S. Gov't |
Journal Detail:
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Title: Journal of plant physiology Volume: 162 ISSN: 0176-1617 ISO Abbreviation: J. Plant Physiol. Publication Date: 2005 May |
Date Detail:
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Created Date: 2005-06-08 Completed Date: 2005-06-29 Revised Date: 2006-11-15 |
Medline Journal Info:
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Nlm Unique ID: 9882059 Medline TA: J Plant Physiol Country: Germany |
Other Details:
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Languages: eng Pagination: 603-6 Citation Subset: IM |
Affiliation:
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Departamento de Botânica, Faculdade de Ciências e Tecnologia, Universidade de Coimbra, 3000 Coimbra, Portugal. crnabais@bot.uc.pt |
Export Citation:
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| MeSH Terms | |
Descriptor/Qualifier:
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Biological Transport, Active Nitrogen / metabolism* Ornithine / physiology* Quercus / metabolism* |
| Chemical | |
Reg. No./Substance:
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7006-33-9/Ornithine; 7727-37-9/Nitrogen |
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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