Plants and the Environment. Solute balance of a maize (Zea mays L.) source leaf as affected by salt treatment with special emphasis on phloem retranslocation and ion leaching
Source: Journal of Experimental Botany, Volume 51, Number 351, October 2000 , pp. 1721-1732(12)
Publisher: Oxford University Press
Strategies for avoiding ion accumulation in leaves of plants grown at high concentration of NaCl (100 mol m-3) in the rooting media, i.e. retranslocation via the phloem and leaching from the leaf surface, were quantified for fully developed leaves of maize plants cultivated hydroponically with or without salt, and with or without sprinkling (to induce leaching). Phloem sap, apoplastic fluid, xylem sap, solutes from leaf and root tissues, and the leachate were analysed for carbohydrates, amino acids, malate, and inorganic ions. In spite of a reduced growth rate Na+ and Cl- concentrations in the leaf apoplast remained relatively low (about 45 mol m-3) under salt treatment. Concentrations of Na+ and Cl- in the phloem sap of salt-treated maize did not exceed 12 and 32 mol m-3, respectively, and thus remained lower than described for other species. However, phloem transport rates of these ions were higher than reported for other species. The relatively high translocation rate of ions found in maize may be due to the higher carbon translocation rate observed for C4 plants as opposed to C3 plants. Approximately 1336% of the Na+ and Cl- imported into the leaves through the xylem were exported by the phloem. It is concluded that phloem transport plays an important role in controlling the NaCl content of the leaf in maize. Surprisingly, leaching by artificial rain did not affect plant growth. Ion concentrations in the leachate were lower than reported for other plants but increased with NaCl treatment.
Document Type: Regular paper
Affiliations: 1: Albrecht von Haller Institut für Pflanzenwissenschaften, Abteilung Biochemie der Pflanze, Untere Karspüle 2, D-37073 Göttingen, Germany 2: Christian-Albrechts-Universität, Institut für Pflanzenernährung und Bodenkunde, Olshausenstrasse 40-60, D-24118 Kiel, Germany 3: Lehrstuhl für Biotechnologie, Biozentrum der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
Publication date: 2000-10-01
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