FLOWERING OF AVOCADO (Persea Americana Mill.). I. INFLORESCENCE AND FLOWER DEVELOPMENT

Abstract

A study of inflorescence and flower development of the ‘Hass’ avocado (Persea americana Mill.) was undertaken in California, USA. Eleven macroscopic stages of external bud and subsequent inflorescence development were correlated with microscopic organogenesis for subsequent use in predicting specific stages of inflorescence development to schedule cultural practices in a commercial orchard. Transition from vegetative to reproductive growth on summer shoots occurred in July-August and was followed by inflorescence initiation from August to October. Anthesis occurred seven months later. A period of dormancy was not required for transition to flowering. At the time of transition, apical buds of mature vegetative shoots consisted of a convex primary axis meristem with two lateral, secondary axis inflorescence meristems lacking apical bracts. Under floral-promoting conditions (low temperature), apical buds fully committed to flowering were not distinguishable anatomically from those that were not committed to flowering. Avocado inflorescence development was correlated with night temperature £ 15 ºC. Crop load influenced the proportion of determinate and indeterminate floral shoots and vegetative shoots produced during spring bloom.