Cotton (Gossypium hirsutum L.) requires warm days and relatively warm nights for optimum growth and development. However, in many areas of the cotton belt, sub- and super-optimal temperatures frequently occur, both early and late in the season, resulting in altered growth and development. The purpose of this research was to quantify plant responses to temperature, so that these responses could be incorporated into plant growth models used to manage cotton crops. Plants, initially grown out of doors in pots, were moved into sunlit, temperature-controlled growth chambers 5 d prior to initial bloom. Growth and development were studied in 20/10,25/ 15,30/20,3S/25, and 40/30 °C day/night temperature regimes from initial bloom. Temperature significantly affected phenology, leaf expansion, internode elongation, biomass production and the partitioning of assimilates to different plant parts. Optimum temperature for biomass production was 30/20 °C, with 40 and 50% less biomass at 20/10 and 40/30 °C, respectively. By 49 d after initial bloom, 13, 15 and 43% of the biomass had been partitioned to bolls and squares at 20/10,25/15 and 30/20 °C, respectively, reflecting to some extent slower development at the temperatures lower than 30/20 °C. Above 30/20 °C, most of the squares and bolls were aborted. The growth of the main-stem and its successive leaves at 30/20 °C was rapid initially, but was restricted later due to competition with bolls for available carbohydrates. The quantification of growth and developmental rates over a wider range of temperatures will enable us to predict crop performance if temperature increases as a result of global climate change.
Contribution from Dep. of Agric. Eng., Clemson Univ., Clemson, SC 29634; Dep. of Agronomy, Mississippi State, MS 39762; and the USDA:ARS Crop Simulation Res. Unit, Crop Sci. Res. Lab., Mississippi State, MS 39762