Cracking of bell pepper fruits is one of the most severe problems affecting their marketable yield. Repeated shrinkage and expansion weakens the fruit cuticle and causes cracking. This study investigated the effects of climatic factors and water stress on the diurnal fluctuation in pepper fruit diameter. Two experiments were conducted in three controlled greenhouses with different air temperatures and relative humidities. The results indicated that the factors affecting leaf transpiration, such as solar radiation, vapour pressure deficit (VPD), air temperature and water stress, affect the timing and amplitude of diurnal fluctuations in diameter of bell pepper fruit. Earlier fruit shrinkage start time (FSST) in the morning, earlier fruit shrinkage ending time (FSET) in the afternoon and larger shrinkage amount were observed in fruits grown in the greenhouse with high night air temperature and low night vapour pressure deficit. Plant root water stress resulted in earlier FSST. Higher incoming radiation increased fruit shrinkage. Sunlit fruits shrank more than those in shade under the same environmental conditions, which is a possible mechanism for more cracking in sunlit fruits. However, no differences of FSST and FSET were observed between fruits in sun and in shade.
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