填空题

Instead of using dye to color cotton, a woman cotton breeder is letting nature do the work. Through crossbreeding ( 杂交 ), Sally Fox of Natural Cotton Colours in Wickenberg is creating plants that yield fiber in a variety of colors. Because no dye is required, production of the naturally colored cotton conserves water and reduces pollution. Fox recently received a United Nations award for her work.
Organically farmed brown and green cottons are already being used to make clothing sold by Levi Strauss, Esprit, and L. L. Bean. The naturally colored cottons are more expensive than conventional cottons, but they do not fade in the laundry.
Fox is also developing a white cotton that can be grown organically. Normally, harvesting white cotton without a chemical defoliant (脱叶剂 ) is extremely difficult, because resin (树脂) on the leaves will stain the fibers. But Fox is growing a variety that naturally sheds (脱去) its leaves prior to harvest. The cotton, close to commercialization, bears long fibers that will be used to make high-quality textile.
Sally Fox plants cotton by (46) to yield color cotton.
The production of naturally colored cotton can (47) and reduce pollution.
The colored cottons are (48) than conventional cottons.
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The white cotton developed by Fox bears (50) .