A comparative study of early fruit abscission on ‘Marsh’ grapefruit and ‘Valencia’ orange under cuban tropial conditions. II. Endogenous approach

Abstract

When studying early fruitlet abscission on ‘Marsh’ grapefruit (<em>Citrus paradise </em>Macf.) and ‘Valencia’ orange (<em>Citrus sinensis </em>L. Osbeck) under Cuban Tropical conditions, gibberellin as well as cellulose peak activities in distal © abscission layer were found. Furthermore, differences between ‘Marxh’ and ‘Valencia’ were also identified, consisting of gibberellin peak delay up to 93.7 days after anthesis (DAA) in ‘Marsh’ grapefruit, at which time fast, exponential fruit growth was coming to an end. Gibberellins peaked in ‘Valencia’ distal zone prior to cellellases. In contrast, maximal cellullase activity levels in ‘Marxh’ distal abscission zone displayed long before gibberellin peak values. On the other hand, high contents of free and conjugated abscisic acid, as well as free jasmonic acid were also found in distal and proximal abscission layers of ‘Marsh? Grapefruit at early stages of fruit development. At the same time, fruitlet abscission through both distal and proximal abscission zones still showed high levels. Whole results obtained could suggest xome cause-effect relationships between endogenous status along fruit pedicel (Gibberellin and cellullase activities, abscisic and jasmonic acid contents, cellullase activity) and delayed ‘Marsh’ fruitlet abscission as compared to ‘Valencia’ orange under Cuban tropical conditions.