THE EFFECT OF PHOSPHATE CONCENTRATION ON GROWTH AND AGAR CONTENT OF GELIDIUM-ROBUSTUM (GELIDIACEAE, RHODOPHYTA) IN CULTURE

Phosphate concentration of the growth medium was found to affect the g rowth rate and agar yield of a clone of Gelidium robustum grown in the laboratory. To study differences in growth we used phosphate concentr ations from 0 to 200 mu M. To determine the effect of phosphate on aga r yield and its properties we used concentrations from 0 to 20 mu M. G rowth rates generally increased with increasing phosphate concentratio n, with the highest growth rate (21% d(-1)) obtained at 150 mu M. Agar yield as percentage of fresh weight was highest (10%) in the algae gr own with low phosphate concentrations, but agar yield as percentage of dry weight was highest (43%) at 20 mu M of phosphate. Gel strength in creased with phosphate concentration with a maximum of 160 g m(-2) for 0.75% gels for the cultures at 20 mu M. Melting and gelling temperatu res of the gels were also affected by phosphate concentration of the g rowth medium. Starch yield was highest in algae grown in low phosphate concentrations.