Water deficit effects during olive tree Inflorescence and flower development

Abstract

An initial step for achieving good fruit production is the formation of a sufficient number of flowers capable of pollination, fertilization and fruit set. We examined the influence of the time of water stress on floral development and quality by withholding water supply during successive periods from winter dormancy until flowering and initial fruit set. The experiments were carried out with three-year-old 'Picual' olive trees growing in a soil peat mixture in 50-L pots, in which control periods were irrigated to replace evapotranspirative loss and soil water content was monitored continuously. Inflorescences and flowers were evaluated at different levels of morphogenetic organization, including inflorescence, ovary and ovule development, and final fruit number and weight determined. Stress during winter dormancy produced no lasting effect and the plants recovered rapidly in response to rewatering. Water deficit during inflorescence development reduced many different flowering parameters, including inflorescence number, flower number, imperfect flower number and percentage, and ovule development, whereas prior to bloom it produced mild or no effects. When water deficit occurred during flowering and initial fruit set, the petals of many flowers dried closed and abscised as a unit, exposing a senescent stigma which was no longer receptive to pollination. Fruit production closely followed flowering parameters, with fruit number low either when flower number was reduced or fertilization inhibited. Fruit size increased with low crop load but not enough to compensate for yield reduction.