The Kinetics of Chloride Accumulation and Transport in Exuding Roots

Publisher Website
Google Scholar
Abstract
Radiocnloride accumulation and transport to the exudation stream in individual exuding onion (Allium cepa) roots was determined for a range of external chloride concentrations. Both chloride accumulation and transport increased with increasing external concentrations according to the standard saturation type curve. Treatment of the data according to Michaelis-Menton enzyme kinetics as employed by Eadie (1942) yielded a curvilinear relationship for both chloride accumulation and transport to the exudation stream. Other workers have interpreted similar functions to mean that 2 separate carriers or carrier sites participate in the transport of a single ion species. However, it was found that the steep portion of the curve in the Eadie plot was obtained only when the external ion concentrations exceeded the tissue or exudate concentrations. In contrast, the flat portion of the curve was obtained only when the external concentrations were less than the tissue or exudate concentrations. Inasmuch as the steep portion of the curve resulted only when external concentrations exceeded internal concentrations it is suggested that the increased uptake of chloride at the high external concentration is not due to the functioning of a separate carrier or carrier site but simply due to an increased uptake of chloride by diffusion.