Influence of water deficits at different times during olive tree inflorescence and flower development

Abstract

Sufficient flower number and quality is a prerequisite for subsequent fruit set, and, in the case of commercial fruit crops, for fruit production. In the olive tree, Olea europaea L. flower development constitutes an extensive process which requires two to three months and includes the elongation and branching of the inflorescence axis and the formation of the individual flowers. We applied controlled water deficit to young olive trees in successive periods from winter dormancy until flowering and initial fruit set, and determined inflorescence, flower, ovary and ovule development and final fruit yield at both morphological and histological levels. Water deficit during winter dormancy had no effect on either flowering or fruiting parameters. Fruit production was reduced in all other treatments, but due to different timing-related causes. Deficit during inflorescence development reduced many different flowering parameters, including inflorescence number, flower number, perfect flower number and percentage, and ovule development. When applied two weeks prior to bloom little change was noted in floral development, but ovary and ovule starch content were reduced as was fruit set. Finally, deficit during bloom-initial fruit set produced a drastic effect in which many flowers remained closed and fertilization was prevented. Overall the results indicated developmental plasticity and compensation among flowering and fruiting parameters, and high sink priority for the ovary tissues.