THE EFFECT OF ISOSAKURANETIN (5,7-DIHYDROXY 4'-METHOXY FLAVANONE) ON POTASSIUM UPTAKE IN WHEAT ROOT SEGMENTS

Isosakuranetin (ISK; 5,7-dihydroxy 4'-methoxy flavanone) is a plant ex udate with known cytotoxic and fungicide properties. When tested on wh eat root segments at concentration of 70 mu M it inhibited K+-dependen t H+ extrusion and net uptake of K+, while leaving the membrane potent ial (PD) unaltered. Fusicoccin (FC)+ISK treatment resulted in a slight membrane depolarization, while ISK alone did not alter O-2 consumptio n or alternative oxidase activity. ISK did not increase the pyruvate c ontent in incubated root tissues or inhibit Fe2+ uptake. The observed drop in K+ net uptake depended on a decrease in K+ influx into the cel l, leading to the suggestion that ISK may act on wheat root segments a s an inhibitor of K+ permeation. The lack of proton leakage and membra ne disruption by ISK made this compound a weak candidate as a phytoale xin, and suggesting a major role as an allelopathic molecule. (C) 1997 Elsevier Science Ltd.