Flower production, fruit set, and physiology of bell pepper during elevated temperature and vapor pressure deficit

High temperature reduces fruit set in bell pepper [Capsicum annuum L. var. annuum (Grossum Group)], and reduction of pepper productivity, resulting fr om high temperature, may be a direct effect of temperature or an indirect e ffect of water stress induced by increased vapor pressure deficits (VPDs) a t high temperature. We evaluated responses of plant growth, reproduction, n et photosynthesis (P-N), chlorophyll fluorescence, predawn respiration, lea f water potential, and stomatal conductance of 'Ace' and 'Bell Boy' bell pe pper to elevated temperature (33 degreesC) with increased VPD (2.1 kPa) or elevated temperature with no increase in VPD (1.1 kPa). VPD had no effect o n flower number or fruit set and did not adversely influence the physiologi cal processes measured. Therefore, deleterious effects of high temperature on pepper fruit set does not appear to be temperature induced water stress, but is more likely a direct temperature response. Elevated temperature dec reased fruit set but not flower production. Gas exchange measurements sugge st failure to set fruit was not due to reduced leaf photosynthesis.