Cuticular cracking in pepper fruit. I. Effects of night temperature and humidity

The objective of the present study was to characterize some of the anatomical and physiological characteristics of fruit cracking in bell pepper (Capsicum annuum L.). Scanning-electron micrographs show that initiation of fruit cracking in bell pepper is by formation of mini-cracks on the cuticle layer; these then enlarge into cracks and traverse the epidermal cells. Pepper cultivars differ in their sensitivity to cracking, partly because of differences in fruit pericarp thickness. Limitation of night transpiration by high humidity or low temperature increased the turgor potential of the fruit pericarp and enhanced cracking. Likewise, leaf pruning suppressed night transpiration and concomitantly increased cracking. Fruit cuticle transpiration was found to be low in the early stages of fruit development and to increase as the fruit became susceptible to cracking. Environmental conditions which enhanced cracking also increased cuticle transpiration in a sensitive pepper cultivar but not in a less sensitive one. We suggest that fruit cracking in bell pepper occurs because reduction in night transpiration causes high turgor pressure in the fruit. As the cuticle becomes permeable to water, the inner turgor pressure causes the cuticle to crack. Differences in cultivar sensitivity may be partly due to differences in pericarp thickness and cuticle properties, but additional factors may be involved.