Epibrassinolide‐inhibition of development of excised, adventitious and intact roots of tomato (<i>Lycopersicon esculentum</i>): comparison with the effects of steroidal estrogens

Abstract

The brassinosteroid, 24‐epibrassinolide, caused observable inhibition of the growth of aseptically‐cultured excised tomato ( Lycopersicon esculentum Mill. cv. Best of All) roots at a concentration of 0.01 μ M . Root formation and outgrowth in tomato shoot cuttings and root biomass in intact tomato seedlings were also depressed by epibrassinolide, but only at a higher concentration (0.1μ M ). Concentrations of the steroidal estrogens, estrone and estradiol (as sulphate derivatives), in excess of 1.0 μ M , reduced cultured root growth as well as root number and total (but not mean) root length in shoot cuttings. Seedling root growth was only slightly inhibited by estradiol but not by estrone. Both epibrassinolide and estrogens caused morphological abnormalities, such as epinasty and leaf‐inrolling in cuttings and seedlings. Epibrassinolide stimulated extension growth of the hypocotyl and epicotyl in cuttings and of the hypocotyl in seedlings, but estrogens exerted no effects on shoot growth.