Endogenous free abscisic acid in floral, bark and leaf tissues of olive during anthesis and early fruit development

Abstract

Endogenous free abscisic acid (ABA) concentrations in floral, bark and leaf tissues of three 20-year-old olive trees ( Olea europaea L. cv. ‘Konservolia’) were determined. The fresh and dry weight per inflorescence reached a maximum with the approach of full bloom. The percentage of perfect flowers between trees varied from 4 to 9.5%. Statistically significant differences were found in the ABA content of olive inflorescence and bark tissues relative to time, but not between trees. The ABA content of the inflorescences was consistently more than 40 nmol per 100 g fresh weight (FW) from early anthesis until full bloom, reaching a maximum 1 week before full bloom. The ABA concentration changes are thought to be due to the shedding of bracts and imperfect flowers, during the period of inflorescence development prior to full bloom. Endogenous ABA concentrations within the inflorescence fell to less than 20 nmol per 100 g FW after full bloom. The ABA content of bark tissues was about 30 nmol per 100 g FW before full bloom. An increase in ABA concentration in bark tissues in late May is attributed to intense shedding of old olive leaves. The ABA content of mature leaves was barely detectable (less than 10 nmol per 100 g FW).