Response of Carbon Metabolism to Night Temperature in Cotton
- Donn A. Warner,
- A. Scott Holaday and
- John J. Burke
Cotton (Gossypium hirsutum L.) is sensitive to low temperatures during all phases of growth. Throughout the cotton growing season on the High Plains of Texas, days provide optimal sunlight and temperature for metabolism followed hy nights with temperatures of 15 to 20°C, well below the optimum. The present growth chamber study compared the response of specific components of C metabolism in vegetative cotton grown with 28°C/28°C and 28°C/20°C day/night regimes. Photosynthesis for cool-night (20°C) plants measured at 28°C the following day was only 77% of 28°C night plants. Less starch accumulation occurred during the day in the cool-night plants, yet their predawn starch levels were approximately 2.5-fold higher than the 28°C plants. Pools of triose phosphate and fructose 1,6-bisphosphate were lower at night at 20°C than at 28°C. The glucose 6-phosphate/fructose 6-phosphate ratio was higher for the cool-night plants, however, indicative of an apparent limitation in sucrose synthesis subsequent to cytosolic fructose 1,6-bisphosphatase. The most interesting observation is the maintenance of equal sucrose pools in both treatments, even though the amount of starch catabolized at night was different. This study shows that cool night temperatures alone alter cotton C metabolism throughout each 24-h period.
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