Effect of external ph and Cl on the accumulation of NH4‐ions in the leaves of sugar beet

Publisher Website
Google Scholar
Abstract
Plants of sugarbeet (Beta vulgaris L. var. Zwanesse) were grown for 3–4 weeks on nutrient solution at constant pH with NH4 as the only nitrogen source. The aim was to study the factors involved in the accumulation of NH4 ions in the leaves. Accumulation of Cl and NH4 in the shoot increased with the pH of the nutrient solution in the range pH 4.0 to 7.0. When plants grown at pH 7.0 were compared with plants grown at pH 5.0, the concentration of Cl in the xylem exudate was increased from 13.7 to 27.2 mmo1/1 and that of NH4 ions from 5.1 to 9.6 mmo1/1. Phosphoenolpyruvate (PEP‐) carboxylase activity extracted from roots of plants grown at pH 7.0 was almost ten times higher compared to plants grown at pH 5.0 and the root and shoot levels of asparagine were increased relative to glutamine. Accumulation of Cl and free NH4 in the leaves was also increased, when the Cl concentration in the nutrient solution was increased from 0.5 to 10 mM/1 at pH 5.0. Results suggest that there is a relationship between the loading of the xylera vessels and the accumulation of free NH4 in the leaves of NH4‐fed beet plants.
Keywords