CHEMICAL-COMPOSITION OF PROTOPLASTS OF LAMINARIA-DIGITATA (PHAEOPHYCEAE)

High numbers of protoplasts were isolated from Laminaria digitata. Pho tosynthetic ability measured by DCMU-enhanced in vivo fluorescence was used as a viability criterium to assess the quality of protoplast iso lation. A new extraction method was developed in order to achieve memb rane disruption and a complete extraction. Seasonal variation in prote in, total carbohydrate and mannitol content was observed in accordance with the variation found in the corresponding plant tissue. Glucose, mannose and galacturonic acid were identified as the major carbohydrat es. Dialysis indicates that 17% of the carbohydrates are polymers. A s urprisingly large fraction of the glucose was dialyzable, 20% of which was found to be free glucose. The most prominent free amino acids are asparagine/glutamic acid, glutamine, alpha-aminoadipinic acid, and al anine. Active peroxidase was detected in all the protoplast isolations .