Cool Temparature Effects on Cotton Fiber Initiation and Elongation Clarified Using In Vitro Cultures

An understanding of the mechanistic basis of adverse environmental effects on cotton fiber development is a prerequisite to future improvement through genetic engineering and aids in field management to minimize such adverse effects. In order to clarify previous results from field studies on the effects of cool temperatures on initiation, early elongation, and later elongation of cotton fibers, cotton ovules ( Gossypium hirsutum L.) cultured in vitro were used as a manipulable and reproducible experimental system based on previous evidence that they provide a valid model. Culture temperature varied from a control of 34 °C constant to 34/15 °C cycling (12/12 h) to mimic a typical diurnal temperature cycle. Fiber initiation and early elongation were analyzed by scanning electron microscopy, and the progress of later elongation was determined by ruler measurements. The results demonstrated that fiber initiation and early elongation (up to about 0.5‐mm length) were independently delayed by cycling cool temperatures, but that later elongation preceded in a temperature‐independent manner. The early delay in fiber development caused by cycling cool temperatures was associated with a longer elongation period during which fibers could attain the control length. Therefore, the results suggest that there are three stages of fiber elongation as distinguished by different temperature responses: initiation, early elongation, and later elongation to attain the genetically determined potential. Consequently, the field temperature during fiber initiation and early elongation may have a profound effect on the final fiber length attained in a limited growing season.