Vegetative & Floral Tissue Development

The animation of floral organogenesis (below) was created by Bridget Lamp and Vito Polito at UC Davis from a series of scanning electron micrographs. It simulates the development of the shoot apical meristem of an almond (Prunus dulcis) flower bud. The developmental sequence begins with the vegetative stage in mid-July and concludes with the completion of floral organ initiation in mid-September.(Lamp et. al. 2001, J. Amer. Soc. Hortic. Sci. 126:689-696).

The plant tissue which develops into leaves, flower buds, or new shoots is called meristem. Both leaves and flowers originate from common meristematic tissue. When a growing shoot begins to develop a flower, the tissue at the tip flattens out and divides into concentric whorls (rings) of cells (Figure 14). In a species with perfect flowers the outer most whorl develops into sepals, the next inner whorl develops into petals, the next whorl develops into the stamen, and the inner-most whorl develops into the pistil (Video 4). Observations of the developmental sequences of vegetative tissue in shoot tips revealed that flowers are essentially leaves that have been modified into reproductive structures.

Although flower tissue is derived from vegetative tissue, the location and type of vegetative tissue which develops into flowers, and ultimately fruits, varies among tree fruit and nut crop species grown in California. An understanding of the bearing habit, or location of buds which form flowers and fruit in individual crop species, is vital to optimizing pruning and training practices in an orchard. The Pruning and Training section of this website includes illustrations and descriptions of the bearing habit of common California fruit and nut crop species.