Net alignment of cellulose in the periclinal walls of the shoot apex surface cells in Kalanchoe blossfeldiana. I. Transition from vegetative to reproductive morphogenesis

The apical dome geometry and the pattern of net cellulose alignment in the periclinal walls of the surface cells of Kalanchoe blossfeldiana were examined during vegetative morphogenesis, during reproductive morphogenesis, and during the transition between the two development states. Photoperiodically induced and noninduced shoot apices were dissected, stained, and viewed under a dissecting microscope. The surface cell layer(s) was removed from the stem apex and examined under a polarizing microscope. The results indicated that correlations exist between the pattern of cellulose alignment on the apex surface and the pattern of organ initiation. Tangential cellulose alignment is always present at the periphery of the shoot apex, and alignment of cellulose at the incipient sites of organ formation is such as to provide circumferential reinforcement for emerging organs. The results also showed that a change in dome geometry is one of the earliest events during the floral transition. This change in geometry is correlated with a change in the pattern of surface cellulose and leads to a change in the developmental state of the apex. Key words: shoot, phyllotaxis, cellulose, flower, organogenesis.