Influence of Glutathione (GSH) on Sulphate Influx, Xylem Loading and Exudation in Excised Tobacco Roots

Publisher Website
Google Scholar
Abstract
In short-term experiments sulphate influx of excised tobacco roots {Nicotiana tabacum L. var. 'Samsun') followed monophasic Michaelis-Menten kinetics with an approximate Km of 12 ± 4 μM and vmax of 657 ± 211 nmol g−1 FW h−1. An inhibition of sulphate influx, xylem loading and exudation of more than 70% was achieved with 01 mM GSH within 1 h. Cysteine was two orders of magnitude more effective as an inhibitor than GSH. An inhibition of more than 75% was already obtained with 1.0μM cysteine. It may, therefore, be assumed that GSH is decomposed to yield cysteine concentrations that may inhibit sulphate influx, xylem loading and exudation. When BSO, a specific inhibitor of the initial step of GSH synthesis, was added, cysteine-mediated inhibition on sulphate influx, xylem loading and exudation was strongly diminished. Apparently, GSH synthesis is required to obtain inhibition of these processes by cysteine. The physiological mechanisms that may cause the inhibition of sulphate influx, xylem loading and exudation by glutathione are discussed.
Keywords

This publication has 0 references indexed in Scilit: