Changes in growth rate, anatomy and polysaccharide content of a sterile form of Tichocarpus crinitus (Gmel.) Rupr. (Rhodophyta, Tichocarpaceae) grownunder differing photon irradiances in the Sea of Japan, Russia

Variations in growth rate, thickness of the internal cortical and medullary cell walls, and carrageenan yield of the red alga Tichocarpus crinitus gro wn under differing. irradiances were studied from June to October, when the algae were present in the non-reproductive sterile form. Growth rates were related to irradiance and seasonal patterns in water temperature. The high est growth rate (2.42% d(-1)) was found in the temperature range 20 - 24 de greesC in August. Optimal irradiance was found to be in the range of 10 - 1 5 % of the incident PAR, i.e. approximately 150-160 muE m(-2) s(-1) at midd ay. Irradiance of approximately 90 % of the incident PAR induced a large de crease in growth rate plus bleaching and tissue necrosis. The thickness of the cortical cell walls showed lar-e variations between light treatments wi th high values being found at low irradiances. In contrast, medullary cell walls showed little change in thickness. Phycocolloid yield had the highest value (35.5 % DM) in August and the lowest value (11 % DM) in October, and was positively related to the growth rate of the algae during the main gro wing season. Data from C-13-NMR and FTIR spectroscopy indicated that the po lysaccharides extracted from the sterile form of T crinitus were predominan tly ii lp hybrid with,type carrageenans. They are localized in the internal cortical tissue of the T crinitus thalli and their accumulation is negativ ely correlated with photon irradiance, which leads to non-gelling polysacch arides predominating at low irradiances.