The Distribution of Hormones in Relation to Apical Dominance in Brussels Sprouts (Brassica oleraceavar.gemmiferaL.) Plants

Abstract

The lateral buds of intact Brussels sprout plants contained less auxin and gibberellin than the main apex. When the apex was removed the auxin content of the top lateral buds increased within 2 days, but gibberellin activity did not increaseuntil shoot extension was apparent. Auxin application to the cut surface of decapitated plants caused lateral bud inhibition, but did not completely prevent bud growth. Both auxin and gibberellin activity in the plant apex decreased with increasing age, but only gibberellin activity decreased in the lateral buds. The auxin content of the lateral buds on intact plants increased with time. It is suggested that in Brussels sprouts, lateral bud inhibition is due to sub-optimal auxin activity, and that decapitation induces an auxin increase in these buds which then grow out. Lateral shoots are produced following decapitation of young plants because the gibberellin content of the lateral buds is relatively high. Only bud swelling occurs in decapitated older plants because the gibberellin content of the buds is too low to stimulate shoot extension. It is concluded that these results support the theory that hormone-induced nutrient diversion may control lateral bud development.