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expression of characteristics of ammonium nutrition as affected by ph of the root mediumTo study the effect of root-zone pH on characteristic responses of NH4+ -fed plants, soybeans (Glycine max inverted question markL. inverted question mark Merr. cv. Ransom) were grown in flowing solution culture for 21 d on four sources of N (1.0 mol m-3 NO3-, 0.67 mol m-3 NO3- plus 0.33 mol m-3 NH4+, 0.33 mol m-3 NO3- plus 0.67 mol m-3 NH4+, and 1.0 mol m-3 NH4+) with nutrient solutions maintained at pH 6.0, 5.5, 5.0, and 4.5. Amino acid concentration increased in plants grown with NH4+ as the sole source of N at all pH levels. Total amino acid concentration in the roots of NH4+ -fed plants was 8 to 10 times higher than in NO3(-)-fed plants, with asparagine accounting for more than 70% of the total in the roots of these plants. The concentration of soluble carbohydrates in the leaves of NH4+ -fed plants was greater than that of NO3(-)-fed plants, but was lower in roots of NH4+ -fed plants, regardless of pH. Starch concentration was only slightly affected by N source or root-zone pH. At all levels of pH tested, organic acid concentration in leaves was much lower when NH4+ was the sole N source than when all or part of the N was supplied as NO3-. Plants grown with mixed NO3- plus NH4+ N sources were generally intermediate between NO3(-)- and NH4+ -fed plants. Thus, changes in tissue composition characteristic of NH4+ nutrition when root-zone pH was maintained at 4.5 and growth was reduced, still occurred when pH was maintained at 5.0 or above, where growth was not affected. The changes were slightly greater at pH 4.5 than at higher pH levels.
Document ID
Document Type
Reprint (Version printed in journal)
Chaillou, S.
(Laboratoire du Metabolisme et de la Nutrition des Plantes, INRA, Versailles Cedex, France)
Vessey, J. K.
Morot-Gaudry, J. F.
Raper, C. D. Jr
Henry, L. T.
Boutin, J. P.
Date Acquired
August 21, 2013
Publication Date
February 1, 1991
Publication Information
Publication: Journal of experimental botany
Volume: 42
Issue: 235
ISSN: 0022-0957
Subject Category
Life Sciences (General)
Funding Number(s)
Distribution Limits
NASA Discipline Life Support Systems
NASA Discipline Number 61-10
Non-NASA Center