Comparison of cell wall composition of tissues from the seagrasses Halophila and Halodule

Abstract

Cell walls from immature and mature roots, leaves and rhizomes of Halophila ovalis (R. Br.) Hook.f., Halophila stipulacea (Forssk.) Aschers. and Halodule uninervis (Forssk.) Aschers. were analysed. Except in roots of Halodule uninervis, all tissues exhibited an increase in the dry weight-fresh weight ratio on ageing, and this was reflected in the yield of cell wall material and cell wall carbohydrate. When expressed as a function of fresh weight, the rhizomes of Halodule uninervis contained approximately twice as much cell wall carbohydrate as any other seagrass tissue analysed. Cell wall carbohydrates consisted mainly of cellulose and uronic acid, the proportions of which increased and decreased respectively as tissue matured. Non-cellulosic neutral sugars contributed between 8 and 15% of the cell wall carbohydrate except in rhizomes of Halodule uninervis where large quantities of non-cellulosic glucose resulted in values between 23 and 31%. In both species of Halophila, tissue maturation led to a decrease in the ratio of non-conjugated phenolics to conjugated ones. Such trends were not easily recognized in the tissues of Halodule uninervis.