ABSTRACT
Cell walls o f red algae are prim arily polysaccharide with a variety o f poly mers represented including galactans, cellulose, m annans, xylans, and com plex mucilages containing glucuronsyl, galactosyl, xylosyl, a variety o f Omethylated glycosyls, and m any other residues [1,2]. As red algae inhabit aquatic environs quite different from those typical o f land plants, it is, perhaps, not unexpected to discover th a t the com position and organization o f their extracellular m atrices are distinct from those com m only encoun tered in the la tter. The m ajority of red algae exam ined share with higher plants the general cell wall form , including cellulosic m icrofibrils embedded in m atrix polysaccharides and other m aterial; however, cellulose is not a m ajor com ponent o f the red algal cell wall. In three instances, cellulose has been found to be not present. Cellulose is replaced with xylan m icrofibrils in one life cycle phase o f Bangia and Porphyra [3-5], and a crystalline m icrofibrillar com ponent appears to be absent from one o f the few unicel lular red algal genera, Porphyridium [6]. In the economically im portan t m arine red algae, the “m atrix” polysaccharide is alm ost entirely m ade up of galactan (carrageenans or agars), which may be highly substituted with sulfate ester groups [1]. M uch discussion has centered on the physiological significance o f this extracellular m atrix in m echanical, hydration, and os m otic regulation in m arine environm ents [2].
