Effects of temperature, irradiance level and nutritional history on the uptake of inorganic phosphorus in Hizikia fusiforme

To investigate the effects of temperature, irradiance level and nutritional history of nitrogen or phosphorus on inorganic phosphorus uptake in Hizikia fusiforme, we cultivated thalli under different conditions, measured the concentration of inorganic phosphorus in media at 0, 0.5^th, 1^st, 2^nd, 4^th, 6^th and 9^th hour, and determined the uptake rate. We set the temperature at 10 ℃, 20 ℃ and 30 ℃, and irradiance levels at 0, 1 500 lx and 6 500 lx in different experiments respectively. Different nutritional histories were obtained by growing thalli at different concentrations of nutrient for 96 h, including 3 levels of phosphorus (0, 5 μmol·L^-1and 50 μmol·L^-1) and 3 levels of nitrogen (0, 10 μmol·L^-1 and 200 μmol·L^-1), respectively. The results show that the uptake rate of inorganic phosphorus reaches maximum at 20 ℃, while the minimum at 10 ℃. With the enhancement of irradiance level, uptake rate increases. Thalli with nutritional history of lower phosphorus concentration show a higher uptake rate of phosphorus, and vice versa. For different nitrogen histories, higher uptake rate is found in alga with higher nitrogen history, and there is no significant difference between 0 and 10 μmol·L^-1 nitrogen histories.