Original paper

Impact of Ni, Zn and Cd on growth rate, photosynthetic activity, nitrate reductase and alkaline phosphatase activity of free and immobilized Scenedesmus quadricauda

Awasthi, Mamta; Das, Debanghshu Narayan


Toxicity of Ni, Zn and Cd has been studied on the green alga Scenedesmus quadricauda. Toxicity was considerably influenced by immobilization of the test organism. All the physiological variables were deleteriously affected in a concentration dependent manner and the metals were found to be more toxic to free state of cells than the immobilized ones. Ni was found to be more toxic to NR and Apase of the test alga compared to the other two metals. A significant variation in the photosynthetic activities in the two states of cells (free and immobilized) was found. A two-fold increase in carbon-fixation of immobilized cells over free cells has been observed specially when supplemented with LC50 of Ni and Cd. O2-evolution was found to be more sensitive to metal toxicity than carbon-fixation in both free and immobilized cells. Metal dependent variation in different processes of free and immobilized cells was also confirmed by the data of statistical analysis ('ANOVA', 3-way).


green algascenedesmus quadricaudacell immobilizationmetal toxicityapasenrphotosynthesis