Temperature regime and carbon dioxide enrichment alter cotton roll development and fiber properties

Temperature and atmospheric carbon dioxide concentration [CO2] affect cotto n (Gossypium hirsutum L.) growth and development, but the interaction of th ese two factors on boil and fiber properties has not been studied. An exper iment aas conducted in naturally lit plant growth chambers to determine the influence of temperature and atmospheric [CO2] on cotton (cv. DPL-51) boll and fiber growth parameters. Five temperature regimes were evaluated: the 1995 temperature at Mississippi State, MS; the 1995 temperature minus 2 deg rees C; and the 1995 temperature plus 2, 5, and 7 degrees C. Daily and seas onal variation and amplitudes were maintained. Atmospheric [CO2] treatments were 360 (ambient) and 720 mu L L-1. Boll number, bell growth, and fiber p roperties were measured. Boll size and maturation periods decreased as temp erature increased. Boll growth increased with temperature to 25 degrees C a nd then declined at the highest temperature. Boll maturation period, size, and growth rates were not affected by atmospheric [CO2]. The most temperatu re-sensitive aspect of cotton development is boll retention. Almost no bell s were retained to maturity at 1995 plus 5 or 7 degrees C, but squares and bells were continuously produced even at those high temperatures. Therefore , the upper limit for cotton boil survival is 32 degrees C, or 5 degrees C warmer than the 1995 U.S. Mid-South ambient temperatures. The 720 mu L L-1 atmospheric [CO2] had about 40% more squares and bells across temperatures than the 360 mu L L-1 [CO2], Fibers were longer when bells grew at less tha n optimal temperatures (25 degrees C) for boll growth. As temperature incre ased, fiber length distributions were more uniform. Fiber fineness and matu rity increased linearly with the increase in temperature up to 26 degrees C , but decreased at 32 degrees C. Short-fiber content declined linearly from 17 to 26 degrees C, but was higher at higher temperature. As for boll grow th and developmental parameters, elevated atmospheric [CO2] did not affect any of the fiber parameters. Changes in temperature, however, had a dramati c effect on boll set and tiber properties. The relationships between temper ature and boll growth and developmental rate functions and fiber properties provide the necessary functional parameters to build fiber models under op timum water and nutrient conditions.