Abscisic acid content of Citrus flavedo in relation to colour development

Summary

The relationship between endogenous abscisic acid concentrations and the development of colour was examined in six cultivars of Citrus sinensis. Abscisic acid content increased throughout the course of colour development and reached a maximum at time of colour break. Late-maturing cultivars accumulated substantially more abscisic acid and development of colour occurred visibly later than in ‘Navel’ selections. A decline in abscisic acid concentration occurred concomitantly with full expression of colour. Analysis of the pigment composition of flavedo from Citrus sinensis cv. Midknight revealed that development of orange colour was associated with a decline in levels of β,β-carotenoids, an increase in violaxanthin monoesters and formation of xanthophyll acyl esters.