Plant fibers: Initiation, growth, model plants, and open questions

Fibers, which are used as a major raw material in the paper industry, as structural components in timber for building, and in the manufacture of wooden items, are among the most important renewable resources. Billions use wood as a major energy source, and fibers are an energy-rich component of wood. They are used for various textiles and as raw material for composites. In this review, I describe the basic characters of fibers, their structure, development, uses, and some of the current major model plants for fiber formation. I discuss open developmental questions and various aspects of further research. Most of the recent progress in the biology of fiber formation, especially in their cell-wall chemistry, emerged from studies of several model plants: Arabidopsis thaliana, Populus sp., Eucalyptus sp., flax, and hemp. I stress the critical need to combine the use of modern methods of research with classical botany. Approaching the issue of fiber formation only by molecular or only by classical methods will not only limit the progress, but may result in critical mistakes. Considering the importance of fibers to humanity, it is surprising how little we know about the biology of fiber formation and how little it is studied as compared, for instance, to the effort to study the genetics and cell biology of flower organ identity.