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      Xylem sap nitrogen compounds of some Crotalaria species Translated title: Compostos nitrogenados da seiva do xilema de algumas espécies de Crotalaria

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          Abstract

          Thirteen species of Crotalaria were analysed for nitrogen compounds in the xylem root bleeding sap. Amino acids were the main form of organic nitrogen found, but only traces of ureides were present. Of the four species analysed for amino acid composition, asparagine was found to be the major amino acid, accounting for over 68% of the nitrogen transported. No striking deviations from this general pattern was found between species, between vegetative and floral stages of development, or between nodulated and non-nodulated plants. It was concluded that the Crotalaria species studied here have an asparagine-based nitrogen metabolism, consistent with many other non-ureide-producing legume species.

          Translated abstract

          Treze espécies de Crotalaria foram analisadas quanto aos compostos nitrogenados presentes na seiva do xilema. Os aminoácidos foram os principais compostos nitrogenados encontrados, e apenas traços de ureídeos estavam presentes. Uma análise da composição de aminoácidos realizada para quatro espécies revelou que a asparagina é o aminoácido predominante, representando mais de 68% do nitrogênio transportado. Nenhum desvio marcante deste padrão foi encontrado entre espécies, entre plantas noduladas e não-noduladas e nem entre estádios florais e vegetativos. Chegou-se a conclusão de que as espécies aqui estudadas possuem metabolismo de nitrogênio baseado na asparagina, concordando com dados da literatura para muitas outras espécies de leguminosas que pertencem à categoria de não-produtoras de ureídeos.

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          Most cited references 14

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          Products of Biological Nitrogen Fixation in Higher Plants: Synthesis, Transport, and Metabolism

           K R Schubert (1986)
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            Nitrogen Nutrition and Xylem Transport of Nitrogen in Ureide-producing Grain Legumes.

            Xylem sap composition was examined in nodulated and nonnodulated cowpea (Vigna unguiculata [L.] Walp.) plants receiving a range of levels of NO(3) and in eight other ureide-forming legumes utilizing NO(3) or N(2) as sole source of nitrogen. A (15)N dilution technique determined the proportions of plant nitrogen derived from N(2) in the nodulated cowpeas fed NO(3). Xylem sap composition of NO(3)-fed, nodulated cowpea varied predictably with the relative extents to which N(2) and NO(3) were being utilized. The ratios of asparagine to glutamine (N/N) and of NO(3) to ureide (N/N) in xylem sap increased with increasing dependence on NO(3) whereas per cent of xylem nitrogen as ureide and the ratio of ureide plus glutamine to asparagine plus NO(3) (N/N) in xylem sap increased with increasing dependence on N(2) fixation. The amounts of NO(3) and ureides stored in leaflets, stems plus petioles, and roots of cowpea varied in a complex manner with level of NO(3) and the presence or absence of N(2) fixation. All species showed higher proportions of organic nitrogen as ureide and several-fold lower ratios of asparagine to glutamine in their xylem sap when relying on N(2) than when utilizing NO(3). In nodulated (minus nitrate) cowpea and mung bean (Vigna radiata [L.] Wilczek) the percentage of xylem nitrogen as ureide remained constant during growth but the ratio of asparagine to glutamine varied considerably. The biochemical significance of the above differences in xylem sap composition was discussed.
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              Crotalaria seed morphology, anatomy, and identification

               R.H. Miller (1967)
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                Author and article information

                Contributors
                Role: ND
                Role: ND
                Journal
                sa
                Scientia Agricola
                Sci. agric. (Piracicaba, Braz.)
                São Paulo - Escola Superior de Agricultura "Luiz de Queiroz" (Piracicaba )
                1678-992X
                July 1999
                : 56
                : 3
                : 733-737
                Affiliations
                [1 ] Universidade Estadual de Campinas Brazil
                Article
                S0103-90161999000300031
                10.1590/S0103-90161999000300031
                Product
                Product Information: website
                Categories
                AGRICULTURE, MULTIDISCIPLINARY

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