This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Web of Science (24) Citing Articles via Google Scholar Google Scholar Articles by Frost, W. B. Articles by Barnett, N. M. Search for Related Content PubMed PubMed Citation Articles by Frost, W. B. Articles by Barnett, N. M. Agricola Articles by Frost, W. B. Articles by Barnett, N. M.

Articles

Cation Pretreatment Effects on Nitrate Uptake, Xylem Exudate, and Malate Levels in Wheat Seedlings ¹

Department of Botany, University of Maryland, College Park, Maryland 20742

Week-old wheat seedlings absorbed at least 40% NO₃^– from NaNO₃ when preloaded with K⁺ than when preloaded with Na⁺ or Ca²⁺. Cultures of Triticum vulgare L. cv. Arthur were grown for 5 days on 0.2 mM CaSO₄, pretreated for 48 hours with either 1 mM CaSO₄, K₂SO₄, or Na₂SO₄, and then transferred to 1 mM NaNO₃. All solutions contained 0.2 mM CaSO₄. Shoots of K⁺-preloaded plants accumulated three times more NO₃^– than shoots of the other two treatments. Initially, the K⁺-preloaded plants contained 10-fold more malate than either Na⁺- or Ca²⁺-preloaded seedlings. During the 48-hour treatment with NaNO₃, malate in both roots and shoots of the K⁺-preloaded seedlings decreased. Seedlings preloaded with K⁺ reduced 25% more NO₃^– than those preloaded with either Na⁺ or Ca²⁺. These experiments indicate that K⁺ enhanced NO₃^– uptake and reduction even though the absorption of K⁺ and NO₃^– were separated in time. Xylem exudate of K⁺-pretreated plants contained roughly equivalent concentrations of K⁺ and NO₃^–, but exudate from Na⁺ and Ca²⁺-pretreated plants contained two to four times more NO₃^– than K⁺. Therefore K⁺ is not an obligatory counterion for NO₃^– transport in xylem.

¹ This research was supported by Project No. K-014 from the Maryland Agricultural Experiment Station. Scientific article No. A2319, Contribution No. 5325 of the University of Maryland Agricultural Experiment Station.