Response of ovule development and post-pollen production processes in male-sterile tomatoes to chronic, sub-acute high temperature stress

In order to determine the effects of high temperature on ovule development and reproductive processes subsequent to pollen production, nine day/night temperature combinations were imposed over a 9 month period as four separate experiments, each with three treatments, including one common treatment. In order to eliminate known effects of high temperatures on pollen production and stylar position, high temperature treatments were applied only to male-sterile tomatoes (Lycopersicon esculentum Mill.). Pollen was obtained from male-fertile plants given optimal growth conditions. This allowed comparison of mean daily temperatures from 25-29 degrees C; day/night temperature differentials (DIFs) of 2, 6, and 10 degrees C; day temperatures of 28, 30 and 32 degrees C at night temperatures of 22, 24, and 26 degrees C; and night temperatures of 22, 24 and 26 degrees C at day temperatures of 28, 30 and 32 degrees C. Average weight per fruit and flower number did not demonstrate a consistent pattern of response to high temperature. Other reproductive characteristics (% fruitset, total number and weight of fruit per plant, and seediness index) decreased as mean daily temperature rose from 25 degrees C to 26 degrees C and from 28 degrees C to 29 degrees C. The primary parameter affecting these variables was mean daily temperature, with day temperature having a secondary role. thus, in determining reproductive responses of tomato to temperatures within this range, day temperature, night temperature and DIFs do not need to be considered independently of their effect on mean daily temperature. If this relationship holds true in other species, and for pre-pollen production processes as well, modelling the effects of projected climate change should be simplified.