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The block composition of alginate from a number of Phaeophyceae from Nova Scotia, Canada, has been determined by circular dichroism analysis. Laminaria longicruris from three different ecological locations shows appreciable morphological variation, which is reflected in differences in alginate composition of the blades. Stipe material shows less variability, but is higher in polyguluronate, consistent with the greater mechanical rigidity of this tissue. Similarly, differences in alginate composition with tissue type and growth location have been observed for L. digitata. Agarum cribrosum shows little tissue-to-tissue variation in alginate composition, material from both blades and mid-ribs being very similar in block structure to commercially available alginate from Macrocystis pyrifera and Ascophyllum nodosum. Stilophora rhizodes and Leathesia difformis , from the order Ectocarpales, both yield alginate of very high polyguluronate content, consistent with the brittle texture of both species. Stilophora rhizoides harvested during two consecutive growing seasons showed no appreciable variation in alginate block structure. Two alginate samples analysed in this work (from Leathesia difformis and from blades of Laminaria longicruris from one of the populations studied) show respectively higher and lower levels of the structure-forming polyguluronate sequences than any previously reported alginate samples from mature plant tissue. |
