Growth and Nitrogen Distribution Patterns in Bean Plants (Phaseolus vulgaris L.) Subjected to Ammonium Nutrition: I. Effects of Carbonates and Acidity Control1
- A. V. Barker,
- R. J. Volk and
- W. A. Jackson2
Growth of bean plants was limited when nitrogen was supplied as (NH4)2SO4 in sand culture in comparison to the growth of plants receiving nitrate nitrogen. Mixing relatively insoluble carbonates with the sand, using (NH4)2CO3 instead of (NH4)2SO4 or maintaining the pH of the nutrient solution near neutrality with NaOH all prolonged the life and increased the growth of plants. Experiments in which C13-labeled carbonate was used revealed no absorption or incorporation of C13 into the plant tissues. The changes in mineral element contents of plant tissue induced by the treatments did not account for the increased growth.
In the absence of pH control, ammonium, amide, and amino acid accumulation was very high in the leaves. Maintaining the pH of the nutrient solution near neutrality stimulated N assimilation in roots, especially the synthesis of amino acids and amides. Acidity control thus prevented the accumulation of ammonium in the tops and hence lessened the possibility of toxic effects from ammonium. The increased conversion of ammonium to nontoxic metabolites in roots is considered to be thedominant process by which acidity control improved the growth of plants on ammonium nutrition.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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