Cortisol and the Adventitious Root Formation in Mung Bean Seedlings

Abstract

Summary The effect of cortisol on the adventitious root formation on the hypocotyls of intact mung bean seedlings and on mung bean cuttings has been studied. Under different physiological conditions cortisol greatly increased the number of adventitious roots formed and also the total number of adventitious roots and initials formed on the hypocotyls of intact mung bean seedlings. The best growth conditions were found to be 25 °C in the dark. In intact seedlings growing in the dark at 25 °C, the cortisol sensitive phase for adventitious root formation was between the second and fourth day of the 6 d growth period. Cortisol was not required during the first day nor after the fourth day of growth. In mung bean cuttings the stimulatory effect of cortisol on adventitious root formation was less pronounced, but there was a significant increase in the total number of roots and initials. In both intact seedlings and cuttings cortisol application provoked a double effect: whereas the formation of initials was stimulated, their outgrowth became limited by the cortisol treatment. Our results suggested that cortisol (or its metabolite[s]) or a factor released by it from the roots was transported to the hypocotyls. The results are discussed in view of the possible occurrence of corticosteroid like compounds in higher plants.