Temperature Effects on Cotton Growth, Reproductive Performance and Fiber Quality.

Temperature is one of the most important abiotic stress factors that affect cotton (Gossypium hirsutum L.) growth and yield. Quantitative functional relationships between temperature and cotton growth, yield, and fiber parameters are needed to improve predictive capability of cotton models. An experiment was conducted in sunlit plant growth chambers to determine the influence of temperature stress on cotton, cv. TM-1, growth, yield and fiber parameters for plants grown at optimum water and nutrient conditions. Four day/night temperature treatments imposed from flowering to maturity comprised of 22/14, 26/18, 30/22, and 34/26 °C representing the boll maturation temperature conditions across the US Cotton Belt. Stem lengths and node numbers were recorded weekly. Cell membrane thermostability, chlorophyll stability, pigments, pollen germination and viability were recorded on recently fully-expanded leaves. Flowers and bolls were tagged to estimate boll maturation period. Plant-component dry weights and boll numbers were recorded at end of the experiment. Relative injury to cell membranes increased with higher temperature treatments while pigments especially carotenoids decreased with increase in temperature. The optimum temperature for total biomass is 26/18 °C and declined at low and high temperatures. The open boll numbers were higher at 30/22 °C and declined sharply at the high temperature. Boll-component weights were greater at 26/18 °C and declined at high and low temperature treatments. Fewer bolls retained at the high temperature were due poor pollen viability and germination. Micronaire, strength, and uniformity increased with increase in temperature up to 26°C and declined at the high temperature except fiber strength which remained the same at the high temperature. Fiber length, on the other hand, increased linearly from 18 to 22 °C, and declined linearly with temperature. The functional relationships between temperature and boll growth and fiber properties will be useful to build fiber models under optimal water and nutrient conditions.