CELL COMMUNICATION, STOCHASTIC CELL RESPONSES, AND ANTHOCYANIN PATTERN IN MUSTARD COTYLEDONS

The role of intercellular signals in plant development was investigate d using phytochrome-induced formation of anthocyanin in cotyledons of white mustard as a model system. The problem was approached by irradia ting different subregions of the cotyledon with a microbeam. This tech nique was combined with in situ hybridization of chalcone synthase mRN A after irradiation of the entire cotyledon. Individual cells that exh ibited all-or-none responses with a resultant stochastic, patchy patte rn were examined during early stages of anthocyanin synthesis. It was demonstrated that the responses of individual cells were subsequently integrated by long-range inhibitory signals. This process led to order ed and gradually developing patterns that could be detected when final stages were analyzed at the whole-organ level. The significance of th ese findings is discussed in terms of efforts toward a general underst anding of photomorphogenesis in plants.