Stimulation of onion root elongation by ascorbate and ascorbate free radical inAllium cepa L.

Abstract

We report that ascorbate free radical stimulates onion root growth at 15 °C and 25 °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, was inhibitory. We show also that ascorbate free radical generated by ascorbate oxidation, is reduced back probably by a transplasmalemma reductase. These results are discussed on the basis of an activation of a transplasma membrane redox system likely involved in processes related to cell growth.