Flower developmental stage and organ sensitivity of bell pepper (Capsicum annuum L.) to elevated temperature

High temperatures adversely affect crop productivity of several plant species including bell pepper (Capsicum annuum L. var. annuum). The objectives of this study were: (1) to determine whether flower ontogeny is adversely affected by high temperature during different phases of development, including pre- and post-pollination events; (2) to determine the duration of high temperature exposure necessary to cause reduction in fruit set; and (3) to determine whether injury to the pistil or stamen during development is responsible for reduced fruit set during big temperature. We determined that flower buds at <2.5 mm in length, corresponding to microspore mother cell meiosis to tetrad dissolution, and flowers that reached anthesis during the high temperature exposure had reduced fruit set when exposed to 33 degrees C for 48 or 120 h. Flower buds at <2.5 min in length also had reduced pollen viability when exposed to 33degreesC for 120 h. Morphological examination demonstrated that meiocytes initiated tetrad formation, but after dissolution the microspores remained small and clumped a thick exine. High temperature exposure at a late-development, pre-anthesis stage did not affect pistil or stamen viability, but high post-pollination temperatures inhibited fruit set, suggesting that fertilization is sensitive to high temperature stress.