Poster: Integrated Plant Biology

Abs # 75: Mechanical wounding and abscission in citrus

Presenter:	Kostenyuk, Igor A, kostenyuk@lal.ufl.edu
Authors	Kostenyuk, Igor A (A)   Burns, Jacqueline K (A)
Affiliations:	(A): University of Florida, CREC

Mechanical wounding causes numerous physiological and molecular reactions in plants related to stress, including abscission. Abscission is a complex process involving a number of genes and signaling pathways that culminates in the removal of organs. Ethylene is considered to be one of the major components involved in the initiation and amplification of abscission. In this study, we have demonstrated that wounding of the fruit peel causes mature fruit loosening and abscission in Citrus sinensis cvs. Valencia and Hamlin. However, wounding of leaves across the blade or abscission zone, or wounding of immature fruit peel had no effect on abscission of these organs. Removal of 27, 51 or 77% of leaf area did not cause leaf abscission. Mechanical injury of the pedicel or calyx did not have a significant effect on fruit detachment force and fruit abscission. Ethylene production was markedly elevated in wounded leaves and fruit. 1-MCP, an inhibitor of ethylene perception, did not prevent wound-induced abscission in mature citrus fruit, although a slight delay in fruit drop was observed. 1-MCP treated wounded fruit produced 3-times the amount of ethylene compared to wounded mature fruit alone, indicating negative feedback regulation of ethylene production in wounded mature citrus fruit. Exposing mature fruit or leaves to continuous ethylene caused abscission in both organs. Application of 1-MCP prior to ethylene treatment prevented leaf abscission but failed to prevent mature fruit abscission. Taken together, the results demonstrate that mature fruit abscission, whether induced by mechanical wounding or ethylene, is insensitive to 1-MCP, suggesting that ethylene plays a minor role in citrus mature fruit abscission.