ABSTRACT
D. P. DELMER Hebrew University o f Jerusalem, Jerusalem , Israel
I. INTRODUCTION
Microfibrils of cellulose are a fundamental component of the cell walls of higher plants, but the process by which 1 ,4 -3-glucan chains are synthesized and then assembled into the cellulose micro fibrils of the wall remains one of the major mysteries of plant bio chemistry. It is still not possible to make preparations from higher plant cells that are able to synthesize, convincingly and reproducibly, either true microfibrillar cellulose Or even appreciable quan tities of any 1 ,4 -3 -glucan shown to be related to cellulose. To a reader from outside this field it may therefore seem that nothing has altered in the last decade, for a review one of us (D . P. D .) wrote 12 years ago (1 ) contains these same comments. However, in spite of the continuing inability to measure any activity of higher plant cellulose synthase in v itro , there is now a considerably clearer understanding of the regulation of the synthesis of this polysac charide in vivo and of the polymeric products that plant membranes do make when provided with the substrate uridine diphosphoglucose (UDP-glucose). In this chapter we present the current state of understanding of plant cellulose synthesis and, in addition, show that a knowledge of how plants change the nature of the polysac charide synthesized at their cell surface is directly relevant to achieving the synthesis of cellulose in v itro .
