9. What is most common use of PGR's? What might be some other ways to accomplish the same goal?
Editor's Notes
(Image of cotton from the 14 th century) Cotton is a soft fiber that grows around the seeds of the cotton plant (Gossypium spp.), a shrub native to the tropical and subtropical regions of both the Old World and the New World. The fiber is most often spun into thread and used to make a soft, breathable textile, which is the most widely used natural-fiber cloth in clothing today. The English name descends from the Arabic word al qutun, (whence also came the Spanish word algodón) meaning cotton fiber. Africa and South America are large providers of cotton. Cotton fiber (once processed to remove seeds and traces of wax, protein, etc.) consists of nearly pure cellulose, a natural polymer. Cotton production is very efficient, in the sense that, ten percent or less of the weight is lost in subsequent processing to convert the raw cotton bolls into pure fiber. The cellulose is arranged in a way that gives cotton fibers a high degree of strength, durability, and absorbency. Each fibre is made up of twenty to thirty layers of cellulose coiled in a neat series of natural springs. When the cotton boll (seed case) is opened the fibres dry into flat, twisted, ribbon-like shapes and become kinked together and interlocked. This interlocked form is ideal for spinning into a fine yarn.