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Temperature Effects on Pima Cotton Growth and Development

Dep. of Agronomy

J. M. McKinion and G. W. Wall

USDA-ARS Crop Simulation Res. Unit, Crop Sci. Res. Lab., Mississippi State, MS 39762.

^* Corresponding author.

An understanding of genetic and environmental factors affecting plant growth and development is needed for accurate yield predictions by crop models. At present there is little information about how Pima cotton, Gossypium barbadense L., a species known for its excellent lint quality, will respond to various temperatures. The objective of this experiment was to determine the growth and developmental rates of Pima cotton plants grown at different temperatures. Pima cotton was grown in 20/12, 25/17, 30/22, 35/27, and 40/32°C day/night temperature cycles in sunlit controlled-environment chambers soon after emergence to 64 d under optimum water and nutrient conditions. Plant heights and mainstem nodes were determined at weekly intervals. Mainstem elongation rates were very sensitive to temperature after about 3 wk following emergence. Prior to that time, the differences were small but measurable. Mainstem node addition rate increased as temperature increased to 40/32°C. The temperature optimum for fruiting branch growth, and square and boll production and retention was 30/22°C. Above 30/22°C, there was an imbalance between vegetative and reproductive growth. Plants became less reproductive at 35/27°C and lost their reproductive ability at 40/32°C. Heat tolerance, as depicted by heat units required to produce first square, is much superior to that reported for Pima, cv. S-2, but slightly less than Upland cotton, cv. DES 119.

Received for publication May 21, 1991.