Regulating Effects of Brassino Steroids and of Sterols on Growth and H+ Secretion in Maize Roots

The effects of brassinosteroid, of twelve related sterols and of three sterols on maize root growth and on H₊ secretion were investigated. A number of steroids stimulated root segment elongation and H₊ secretion as brassinosteroid does. Defined structural requirements were found for the effect on growth; on the contrary, all the steroids tested, among which stigmasterol, cholesterol and ergosterol, were active on H₊ secretion. Cholesterol stimulated K₊ uptake and dark CO₂ fixation, two processes generally associated with the activity of the H⁺ pump.