Temperature effects on early season cotton growth and development

Temperature is a primary environmental factor controlling growth and developmental rates of plants, yet little specific information is available regarding cotton (Gossypium hisutum L.) responses to temperature. Information covering a wide range of temperatures would be useful for predicting both developmental and growth rates in cotton. Therefore, an experiment was conducted in naturally lit, temperature- and CO2-controlled cabinets from soon after emergence until 56 d after emergence (DAE). The cabinets were maintained at 20/12, 25/17, 30/22, 35/27, and 40/32C day/night cycles. Plant heights, number of nodes, and leaf areas were determined weekly throughout the experiment, and dry weight measurements were obtained at three intervals. Mainstem elongation, leaf area growth, and biomass accumulation rates were very sensitive to temperature about 3 wk after emergence. Prior to that time, they were relatively insensitive to temperature. The temperature optimum for stem elongation, leaf area expansion, and biomass accumulation was 30/22 C. Developmental rates, as depicted by number of mainstem nodes produced, number of fruiting branches, and fruiting branch nodes, were not as sensitive to temperatures above 30/22 C as were growth rates. Four times as many fruiting branches were produced at 30/22 C as at 20/12 C; whereas more vegetative branches were produced at low temperatures. All flower buds abscised from plants grown at 40/32 C. Essentially, all bolls and squares were retained at 30/22 C while a 10% boll and square loss was observed at 35/27 C during the early reproductive period. Less time was required for this cultivar to produce squares at any temperature, suitable for growing cotton, than was suggested by previous experiments