FLOWER INITIATION IN ‘MANZANILLO’ OLIVE

To date, the accumulated data on flower initiation in olive point to factors occurring during or after dormancy and winter chilling of the undifferentiated buds. We have investigated flowering in ‘Manzanillo’ olive trees using anatomical and quantitative cytochemical methods to determine the timing of floral initiation as indicated by structural changes in the axis of the buds and in levels of cellular RNA within the apical meristem of these buds. Material was collected weekly from nonbearing trees, with heavily bearing trees that did not flower the following spring serving as controls. Buds were prepared for standard anatomical and morphological analyses, and for quantitative cytochemical analysis using Cuprolinic Blue-staining for RNA. Results showed increases in bud size and number of nodes within buds from nonbearing trees, development of lateral buds on the inflorescence axis, as well as a two-fold increase in cellular RNA in cells of the central zone of the shoot apical meristem of buds from nonbearing as compared to bearing trees.