XVI International Botanical Congess

Spontaneous mutations can be reproductively isolated when they occur in the shoot apical cell layers that do not give rise to gametes and, therefore, have no impact on evolution. A characterized genetic mosaic was subjected to different degrees of simulated herbivory to determine the fate of cells in shoot apices of axillary buds. Destruction of terminal and primary axillary buds resulted in the outgrowth of secondary axillary buds present in the same node as the primary bud. Seed derived from secondary buds was not always descended from the second apical cell layer of the terminal shoot meristem as was true for terminal and primary buds. Vegetative and reproductive analysis indicated that secondary buds did not maintain the same order of cell layers present in the other buds. Cells were repositioned into gamete-forming layers. Herbivores feeding on shoots and buds may influence plant evolution by causing the outgrowth of secondary buds.