Nitrogen assimilation in citrus trees |
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Authors: | TADASHI KATO |
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Institution: | Shikoku National Agricultural Experiment Station, Plant Nutrition Laboratory. Kagawa-ken, Zentsuji 765, Japan |
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Abstract: | Assimilation of 15N-ammonium and 15N-nitrate was examined in 3-year-old satsuma mandarin (Citrus unshiu Marcovitch) trees. Experiments were designed to establish the time course of incorporation of nitrogen just taken up into amino compounds. In fine roots, absorbed 15N-ammonium was actively incorporated into glutamine and then into glutamic acid and asparagine. When feeding 15N-nitrate, glutamic acid and asparagine were actively synthesized, but glutamine synthesis was comparatively low as compared with that in ammonium feeding. In current leaves and fruits, a clear difference in the labelling patterns of amino acids was found between the ammonium and nitrate feedings. The amino acid most markedly labelled was asparagine in the ammonium feeding and glutamine in the nitrate feeding. Considering the most heavily labelled component in leaves and fruits, the main form of the nitrogen components transported upward in the xylem was discussed. |
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Keywords: | Nitrogen assimilation 15N-ammonium 15N-nitrate Amino acid Citrus tree |
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