Fe-EDTA Reduction in Roots of Plantago lanceolata by a NADH-dependent Plasma Membrane-bound Redox System

Abstract

Plasma membrane vesicles were isolated from roots of Plantago lanceolata L. by aqueous polymer twophase partitioning. Fe-EDTA reduction was measured using bathophenanthrolinedisulfonate (BPDS) as an Fe 11 indicator. The reaction is dependent on NADH and stimulated by Triton X-100 by about 5-fold. In contrast to intact plants, the reduction rate is not enhanced in plasma membrane vesicles from irondeficient plants when expressed as specific activity. Kinetics of the reaction performed by intact roots are very similar to those of in vitro measurements with isolated plasma membrane vesicles. These results indicate that Fe III reduction by roots of Plantago lanceolata takes place at the plasma membrane by an enzymatic process which uses internal NADH as the electron donor.