INHIBITION OF ETHYLENE PRODUCTION IN SUNFLOWER CELL-SUSPENSIONS BY THE PLANT-GROWTH RETARDANT BAS-111..W - POSSIBLE RELATIONS TO CHANGES INPOLYAMINE AND CYTOKININ CONTENTS

At a concentration of 10(-5) mol . L-1 the triazole-type growth retard ant BAS 111..W completely inhibited the transiently elevated ethylene production in the exponential growth phase of heterotrophic sunflower cell suspensions. This effect, which could not be restored by adding g ibberellin A3, was accompanied by transiently increased levels of 1-am inocyclopropanecarboxylic acid (ACC) in the cells, which was increasin gly converted to N-malonyl-ACC. Thus, the reactions from ACC to ethyle ne catalyzed by the ethylene-forming enzyme appeared to be blocked by the retardant. Concomitantly, higher endogenous levels of free spermid ine and particularly spermine were found over control, whereas free pu trescine, the direct precursor of both polyamines, simultaneously decr eased. We assume that the remaining S-adenosylmethionine from ethylene biosynthesis was increasingly incorporated into spermidine and finall y spermine. A further relation appears to exist between the reduced et hylene production and enhanced levels of cytokinins in the cells. The application of both BAS 111..W and aminoethoxyvinylglycine depressed e thylene formation while immunoreactive cytokinins from isopentenyladen osine-, trans-zeatin riboside-, and dihydrozeatin riboside-type increa sed. By additional treatment with ACC, the effects could partially be reversed. On the other hand, stimulation of ethylene production by ACC alone or ethephon considerably lowered cytokinin levels.