Effects of climatic factors and water stress on the diurnal fluctuation indiameter of bell pepper fruit

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 climat ic factors and water stress on the diurnal fluctuation in pepper fruit diam eter. Two experiments were conducted in three controlled greenhouses with d ifferent air temperatures and relative humidities. The results indicated th at the factors affecting leaf transpiration, such as solar radiation, vapou r pressure deficit (VPD), air temperature and water stress, affect the timi ng and amplitude of diurnal fluctuations in diameter of bell pepper fruit. Earlier fruit shrinkage start time (FSST) in the morning, earlier fruit shr inkage 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 conditi ons, which is a possible mechanism for more cracking in sunlit fruits. Howe ver, no differences of FSST and FSET were observed between fruits in sun an d in shade.