Iron reduction and uptake by grapevine roots

Some characteristics of Fe reduction and uptake by grapevine roots were studied by comparing them with K+ uptake and with ion uptake by oat roots. BPS inhibits Fe uptake by more than 90 percent both in grapevine and oat roots. However, the Fe reducing capacity of membrane vesicles “in vitro” is also inhibited by BPS. Compounds interfering with electron flows (DCMU, PMS, ferricyanide) also inhibit Fe uptake. Anaerobiosis increases the reducing activity of grapevine roots. Oligomycin inhibits Fe reduction in the presence of O2 and stimulates it under anaerobiosis. Rotenone inhibits Fe uptake both in aerobic and anaerobic conditions. Fe and K uptake rates by grapevine roots are not constant. A first phase at higher rate occurs within the first minutes, a second phase follows at a lower rate. With oat roots Fe behaves similarly, while K uptake occurs at a constant rate. Lowering the temperature from 30 to 0°C decreases the absorption of Fe and K by grapevine roots by about 50%. Fe uptake by oat roots decreases by 75 percent and K uptake by about 90 percent. Fe absorption by different grapevine species is characterized by wide differences in the kinetic constants (Vmax and Km) and in the response to changes of pH. The biochemical basis of Fe reduction and the distinctive features of Fe uptake by grapevine roots are discussed