Structural studies of Chondrus crispus: the effect of extraction of carrageenan

Birefringence, energy-dispersive x-ray analysis (EDX), and ultrastructural studies were performed on control and on extracted carposporic and tetrasporic Chondrus crispus Stack. thalli.EDX analysis of untreated carposporic and tetrasporic plants revealed the presence of sulphur primarily in the intercellular matrix and cell walls. The sulphur levels detected were greater in tetrasporic than in carposporic plants. EDX analysis of tetrasporic and carposporic plants after extraction with hot aqueous bicarbonate, which should remove most of the sulphated polysaccharide carrageenan, showed little sulphur in walls and intercellular matrices.The microfibrils visible with transmission electron microscopy in cell walls of both generations of C. crispus appeared to run parallel to the cell surface, i.e. circumferentially. Some areas of the intercellular matrix were entirely granular, while others contained microfibrils. After extraction, microfibrils in cell walls and intercellular matrix were disorganized but were still present, perhaps in reduced amounts.The birefringence which characterized the walls of untreated cells was greatly reduced by 2 h extraction, and matrix birefringence was entirely removed. Cortical cell walls could still be identified and stained metachromatically with toluidine blue, but they were no longer birefringent. Further extraction (5 h) removed residual birefringence, but rhizoid cell walls were still metachromatic, as were the remnants of small cells believed to be cortical in origin.