Permanent address: Centro de Ecofisiología Vegetal, Serrano 661, 1414 Buenos Aires, Argentina.
EFFECT OF CATIONS ON UPTAKE, TRANSLOCATION AND REDUCTION OF NITRATE IN WHEAT SEEDLINGS
Article first published online: 2 MAY 2006
Volume 99, Issue 3, pages 367–379, March 1985
How to Cite
BARNEIX, A. J. and BRETELER, H. (1985), EFFECT OF CATIONS ON UPTAKE, TRANSLOCATION AND REDUCTION OF NITRATE IN WHEAT SEEDLINGS. New Phytologist, 99: 367–379. doi: 10.1111/j.1469-8137.1985.tb03665.x
- Issue published online: 2 MAY 2006
- Article first published online: 2 MAY 2006
- (Accepted 28 October 1984)
- ion balance;
- Triticum aestivum;
- xylem exudate
The effect of Ca2+, K+ and Na+ on uptake, transport and reduction of NO3− was studied in 10-day-old plants of Triticum aestivum L. cv. Sicco grown in water culture in relation to the ion balance in plant, medium and xylem exudate.
When Ca2+ (0.25 mM) was the only nutrient cation, NO3− uptake and accumulation of NO3− in the leaves were low as compared to treatments with K+ or Na+ (0.5 mM). With Na+, the uptake of NO3− was similar to that with K+, but virtually no Na+ and 75 % less NO3− accumulated in the leaves.
Medium pH dropped initially with 0.5 mM KNO3 but rose immediately when Ca2+ was the only cation. The carboxylate content rose in roots and leaves of K+ plants and, to a lesser extent, in Na+ plants. Roots of Ca(NO3)2 plants showed negative ash alkalinity indicating the presence of acidity.
The pH of the xylem exudate increased with the cation/NO3− ratio in the exudate and was about one unit higher with Ca(NO3)2 than with NaNO3 or KNO3.
We conclude that roots of plants grown in the absence of monovalent cations have serious pH problems because of a high rate of alkalinity release to the medium in exchange for NO3− uptake, and the secretion of alkalinity into the xylem.