INFLUENCE OF HYDRODYNAMIC ENVIRONMENT ON COMPOSITION AND MACROMOLECULAR ORGANIZATION OF STRUCTURAL POLYSACCHARIDES IN EGREGIA-MENZIESII CELL-WALLS

To test whether secondary and tertiary structures of marine-algal stru ctural polysaccharides may be altered during adaptive responses to hyd rodynamic stresses, juvenile Egregia menziesii (Turn.) Aresch. sporoph ytes were cultured under three different regimes: (i) low-energy (LE) specimens were subjected to water motion produced by standard bubbling and circulation of tank water; (ii) high-energy (HE) specimens receiv ed additional movement in pumped streams of water; and (iii) stretched (STR) specimens were grown under low-energy conditions but also were subjected to constant, longitudinal tension (0.7 N). After 6-10 weeks growth, cell-wall structural polysaccharides from specimen blades were isolated by solubilizing less-ordered matrix polysaccharides. Neutral -sugar and uronic acid contents of these isolates were measured, and s amples were analyzed by x-ray diffraction and by Raman and C-13-nuclea r magnetic resonance (NMR) spectroscopy. On average, structural polysa ccharides formed about 7.2% of dry-weight biomass. The portion of isol ated mass accountable to neutral sugars ranged from an average of 85% for STR sporophytes to 94% for both LE and HE specimens. For all speci mens, glucose composed an average of 99% of this fraction. Uronic acid s could not be detected in isolates from any treatment group. Cellulos e dominance in each isolate was indicated clearly in x-ray diffraction patterns and in Raman and C-13-NMR spectra. These data further demons trated that both the cellulose I allomorph and the disordered form of the polymer were present in each isolate and that the STR isolate cont ained small quantities of the cellulose II allomorph. In general, the LE and HE samples had very similar crystallinity; lateral order was sl ightly more developed in LE samples. However, the STR treatment produc ed cellulose with lowest crystallinity and least lateral order. Result s suggest that mechanical stress modified cellulose crystallinity in t hese kelps by altering levels of disordered cellulose and lateral dime nsions of cellulose crystallites and, in one instance, changed the cry stallinity qualitatively. Physical disturbances to cell plasma membran es may have instigated these trends. In the STR specimens in particula r, such disturbances might have been supplemented by fundamental chang es to kelp physiology, affecting both substantial decreases in crystal linity and production of the cellulose II allomorph. Changes in the na ture of the cellulose cannot, however, account for changes in the elas tic moduli.