STIMULATION OF ONION ROOT ELONGATION BY ASCORBATE AND ASCORBATE FREE-RADICAL IN ALLIUM-CEPA L

We report that ascorbate free radical stimulates onion root growth at 15 degrees C and 25 degrees C. The fully reduced form, ascorbate, also stimulates root elongation if culture conditions allow its oxidation. When ascorbate oxidation was inhibited, no stimulation of root growth was found. The effect of the fully oxidized form, dehydroascorbate, w as inhibitory. We show also that ascorbate free radical generated by a scorbate oxidation, is reduced back probably by a transplasmalemma red uctase. These results are discussed on the basis of an activation of a transplasma membrane redox system likely involved in processes relate d to cell growth.