RESPONSE OF OVULE DEVELOPMENT AND POST-POLLEN PRODUCTION PROCESSES INMALE-STERILE TOMATOES TO CHRONIC, SUBACUTE HIGH-TEMPERATURE STRESS

In order to determine the effects of high temperature on ovule develop ment 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 on e common treatment. In order to eliminate known effects of high temper atures on pollen production and stylar position, high temperature trea tments were applied only to male-sterile tomatoes (Lycopersicon escule ntum Mill.). Pollen was obtained from male-fertile plants given optima l growth conditions. This allowed comparison of mean daily temperature s 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 temperature s of 22, 24 and 26 degrees C at day temperatures of 28, 30 and 32 degr ees C. Average weight per fruit and flower number did not demonstrate a consistent pattern of response to high temperature. Other reproducti ve characteristics (% fruitset, total number and weight of fruit per p lant, and seediness index) decreased as mean daily temperature rose fr om 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 temper ature, with day temperature having a secondary role. thus, in determin ing reproductive responses of tomato to temperatures within this range , day temperature, night temperature and DIFs do not need to be consid ered independently of their effect on mean daily temperature. If this relationship holds true in other species, and for pre-pollen productio n processes as well, modelling the effects of projected climate change should be simplified.