CHARACTERIZATION OF MAIZE DEFECTIVE KERNEL (DEK) MUTANTS AFFECTING SEED-GERMINATION

A group of maize defective kernel (dek) mutants, defective in embryo a nd endosperm development and showing altered or suppressed germination , was characterized with the aim to identify genes involved in embryog enesis and related to hormone action. The defects in seed germination and seedling establishment were explored using two different approache s: by analyzing enzymes that exhibit a well defined pattern of tempora l expression in the scutellum during germination (catalase-2, malate s ynthase and glutamine synthetase), and by examining the response of de veloping embryos to a specific class of growth regulators, the cytokin ins. Mutants fall into mio groups according to their ability or inabil ity to induce enzymes involved in tile germination process during imbi bition. The morphogenetic response to cytokinins of mutant embryos var ied in the different mutants analyzed. The strongest response was obse rved with the mutant ed41 which was defective in the differentiation of shoot apex: in the presence of cytokinins, normal seedling growth w as restored. The phenotype of ed41 and its response to cytokinins sug gest that this mutant is impaired in cytokinin mediated processes.