Date of Award

1996

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Plant, Environmental Management and Soil Sciences

First Advisor

Carl E. Motsenbocker

Abstract

Two genotypes of cayenne pepper, Capsicum annuum L., were identified that differ significantly in ease of fruit detachment. Both greenhouse and field-grown plants of these genotypes, Cajun 1-9027 and Cap-9004, were investigated for differences in cell type and organization at the fruit-receptacle junction. Scanning electron microscopy revealed that mature fruit of Cajun 1-9027, which did not separate, exhibited a distinct region of sclerified cells that extended from the periphery of the fruit into the receptacle for at least 15 cell layers. In contrast, mature fruit of the more readily detachable Cap-9004 had fewer sclerified cells at the region of detachment. Both histochemical and stereological techniques indicated Cajun 1-9027 had a greater volume of sclereids than Cap-9004. Neither genotype exhibits a well-defined abscission zone at maturity in the detachment region. The presence of more sclerified cells and increased lignification in Cajun 1-9027 compared to Cap-9004 probably contributed to the differences in ease of detachment between the two genotypes. The usefulness of ethephon, an ethylene releasing compound, as a potential tool in increasing ease of fruit detachment between the receptacle and fruit was also investigated. Ethephon treatments to mature fruit resulted in enhanced maturation, as indicated by fruit color changes, in both genotypes. There were no differences however in fruit detachment force between ethephon treated and untreated fruit. Examination of sclereid development indicated differentiation by two weeks after anthesis in both genotypes. Sclereid development continued as fruits matured with an increasing trend for both genotypes through nine weeks after anthesis. However, genotypic differences were observed after week nine. In Cajun 1-9027 sclereid volume density increased reaching a sclereid volume density higher than 50% at maturity, thirteen weeks after anthesis. Cap-9004, in contrast, did not increase in sclereid volume density beyond nine weeks after anthesis and sclereid volume density remained near 35%. There were significant differences in sclereid volume density between the two genotypes by thirteen weeks after anthesis.

ISBN

9780591133561

Pages

109

DOI

10.31390/gradschool_disstheses.6251

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