中文摘要：

在实验室培养条件下，研究了不同氮、磷浓度及氮磷比结构对东海原甲藻生长和藻细胞硝酸还原酶活性（NRA）的影响．结果表明，各培养组藻细胞在接种后d2即进入指数生长期，但受氮、磷浓度及结构的影响，各培养组的比生长率和藻密度存在一定的差异．同东海原甲藻的生长类似，藻细胞的NRA也受氮、磷浓度及结构的影响．研究进一步发现，东海原甲藻硝酸还原酶活性的最大值（NRAmax）都出现在指数生长期，与最大比生长率出现时间基本一致，且当N／P=16时，酶活力有最大值，表明东海原甲藻的硝酸还原酶活性存在一定阈值．此外，藻的生长速率与营养盐的同化速率并不一致，存在一定的滞后效应．

英文摘要：

The growth and nitrate reductase activity （NRA） of Prorocentrum donghaiense were investigated under different levels and ratios of nitrate and phosphate. The results indicated that the cells of P donghaiense multiplied exponentially just in the second day after inoculation in all test groups. But, there were some differences between the specific growth rate and cell density in each group because of the different levels and ratios of N and E Similarly, the NRA of P donghaiense was also affected by both the levels and ratios of N and E The results also revealed that the appearing time of NRAmax and the maximum specific growth rate were basically consistent that both appeared in the period of exponential growth. The NRAmax was the largest at the level of N/P=16 which suggested that the NRA of P. donghaiense had a certain threshold. In addition, the growth of P donghaiense had a lagging effect which was not consistent with the assimilation of the nutrients.