Abstract
Recent applications of molecular techniques to the study of brassinosteroid action have enhanced our understanding of these unique plant growth regulators. The cloning of genes regulated by brassinosteroids has revealed novel information on the control of gene expression by plant steroids and has extended our knowledge of brassinosteroid‐promoted cell expansion. The analysis of brassinosteroid‐deficient and brassinosteroid‐insensitive mutants has implicated these growth regulators in a number of essential developmental programs including organ elongation, leaf development, photomorphogenesis, fertility, apical dominance and vascular differentiation.