| A reduction in fruit set has been attributed to high temperature for many plant species, including sweet, bell pepper (Capsicum annuum L.). Researchers have associated the reduction in fruit set of pepper to an increase in flower bud and flower abscission at high temperatures. The objectives of this thesis were to: (1) characterize the effects of high temperature and vapor pressure deficit (VPD) on flower production, pepper fruit set and plant physiology; (2) determine whether high temperature inhibits flower initiation, increases flower bud abscission or increases flower abscission; (3) identify the stage(s) of flower development sensitive to high temperature and the duration of exposure which inhibits fruit set; (4) distinguish between injury to the pistil and/or stamen versus the inhibition of post pollination events. An increase in VPD, from 1.1kPa to 2.2kPa, at 33°C did not affect leaf gas exchange or leaf water relations. All peppers grown at 33°C produced flower buds, which generally reached anthesis, but failed to set fruit. Pepper flowers exposed to high temperature for 48 hours or longer at different stages of development were sensitive during early flower development, when microspore mother cells (MMC) are undergoing rneiosis, and during anthesis. Damage to the stamen by high temperature during early flower development, resulting in nonviable pollen, was responsible for the reduction in fruit set, fruit size, and seed number. Damage to the pistil by high temperature was minimal, and resulted in reduced seed number, only. I identified through morphological examination that microspore tetrads are formed during the five-day, high temperature exposure, but dissolution of the tetrads after the high temperature treatments resulted in mostly clumped, aborted microspores. Reduced fruit set of flowers exposed to high temperature during anthesis was not attributed to damage of the stamen or pistil prior to pollination, but caused by inhibition of fertilization and early fruit development. |
