9304369 Green This proposal addresses the mechanisms for expression of pattern in the plant shoot. The aim is to explain a) the origin of pattern, b) its propagation, i.e. phyllotaxis, and c) change of pattern as in flower mutants. Organ pattern is first seen in the arrangement of folds or bumps in the surface layer of the apical dome, the tunica. Current theory usually postulates that a chemical pre-pattern is first generated by diffusing inhibitors or morphogens and then converted, congruently, to solid tissue configuration. It is proposed here to further pursue an alternate hypothesis where pattern is directly generated in the tissue itself by physical laws of the solid state, i.e. buckling theory based on the von Karman equations. The research plan is as follows: Selected developmental progressions will be characterized by a non-destructive SEM replica technique to determine the precise course of tissue folding and cell growth in vivo. Parallel computer simulations will determine the extent to which buckling theory can account for the observed progressions. Dr. Green will study vegetative shoots and morphological floral mutants (concentric and blind in Petunia). Further testing involves responses to physical constraint and the local application of morphogenetically active compounds. This research will clarify the biophysics of morphogenesis and its modulation by diffusing agents. ***
