The detrimental effects of cool temperatures on cotton fiber development have been known for many years. In plant grown fibers, cold temperatures have been reported to affect the rate of boll maturation, rate of fiber elongation [7], final accumulation of cellulose, and various fiber properties [summarized in 3]. At the molecular level, fiber development at cold temperatures has been correlated with decreased crystallinity and molecular weight of cellulose [for example, 5]. Our studies are directed towards understanding the cellular mechanism by which low temperatures affect fiber development. We are particularly interested in the effects of cycling temperatures, such as those encountered by field crops. Such diurnal temperature fluctuations have been correlated with the occurrence of "growth rings" that are visible in swollen cross sections of field grown fibers (e.g., 1, 6].