Abstract
The loading of amino acids and nitrate into the xylem was investigated by collection and analysis of root-pressure exudate from the cut hypocotyl stumps of seedlings of Ricinus communis L. Glutamine was found to be the dominant amino acid in the exudate and also to be the amino acid which is transferred to the xylem most rapidly and accumulated to the greatest extent. The comparison between uptake and xylem loading showed significant differences in specificity between these two transport reactions, indicating a different set of transport systems. Nitrate is transferred to the xylem at a higher relative rate than any amino acid despite the great nitrate-storage capacity of the root system. Thus the supply of nitrate to Ricinus plants leads to enhanced nitrogen allocation to the shoots.
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This work was generously funded by Deutsche Forschungsgemeinschaft. The technical help in the amino-acid analysis by R. Veith, in nitrate analysis by W. Kaiser, and in some exudation experiments by T. Sakuth and M. Schwarz is gratefully appreciated. We are indebted to A. Phelps for reading the manuscript and improving the English style.
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Schobert, C., Komor, E. Transfer of amino acids and nitrate from the roots into the xylem of Ricinus communis seedlings. Planta 181, 85–90 (1990). https://doi.org/10.1007/BF00202328
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DOI: https://doi.org/10.1007/BF00202328