Cuticular cracking in bell pepper fruit: II. Effects of fruit water relations and fruit expansion

The objective of this research was to study the role of fruit expansion and turgor in the formation of cuticular cracking in bell pepper (Capsicum ann uum L.). Fruit was artificially cracked by filling detached hollowed pepper fruits with distilled water. However, when isotonic mannitol solution was used, cracking did not occur. Similarly, immersion of intact red fruits in tap water caused formation of cuticular cracks following a delay of 30 h du ring which the turgor potential of the red pericarp and the expansion of th e fruit diameter increased to critical threshold values of 0.65 MPa and 1-2 %, respectively. On the other hand, in the greenhouse, attached red fruits underwent diameter change of only 0.2% and, when most expanded, the fruit h ad a turgor potential of only 0.3 MPa. In greenhouse grown plants, pepper f ruits become susceptible to cracking at the stage of colour turning, a stag e at which they also become susceptible to artificially induced cracking by immersion in water. Under greenhouse conditions both young and mature frui ts exhibited growth independent of diurnal diameter fluctuations. Larger di ameter fluctuations were observed in mature fruit, under conditions which e ncouraged cracking. Based on these results, we suggest that it is the magni tude of the diurnal fluctuations in fruit turgor and diameter, continuing o ver a long period which may cause the splitting of the cuticle.