The Response Of Nitzschia Palea To Light Quality And Lead

With the development of society and people’s lack of knowledge about lead pollution, the contamination of lead in the environment is getting increasing. Diatoms are widely present on Earth where there is water, and play a role in monitoring the extent of water pollution as biological indicators. This study selected the Nitzschia palea as experimental material, and tried to research the growth of Nitzschia palea with different light quality, so as to provide the basis about the supplymentary lighting in diatoms’ culture. In addition, we conducted tests about the effects of the diatom’s growth and physiology with different concentrations of lead, and the key piont is study the movement, so as to provide the basis for the evaluation of lead’s ecological risk in water scientificly. The main conclusions were as follows:（1）Effects of different light quality on N. palea growth: light intensity was 100 lux, blue light can promote the growth of N. palea, and is conducive to the accumulation of chlorophyll a content of diatoms, then followed by red light.（2）The effect of different Pb²⁺ concentration on N. palea growth and chlorophyll a content: the low concentration of Pb²⁺ can promote the growth of N. palea, the high concentration of Pb²⁺ can inhibit the growth of N. palea. In this study,the value of 96 h EC50 of N. palea was 27.26 mg/L. According to the toxicity grading standards evaluation of algae growth inhibition in "water and wastewater monitoring and analysis methods the fourth edition", it was the middle toxicity level. The results of experiments showed that, when the Pb²⁺ concentration was less than 10 mg/L, it was good for the accumulation of chlorophyll a content of N. palea. However, it would destroy chloroplasts of diatom cells with excess Pb²⁺, and inhibit the synthesis of chlorophyll, which led to chlorophyll a content decreased, thereby reduced the efficiency of the cells’ photosynthetic.（3）The effect of different concentrations of Pb²⁺ on the living cells’ morphology of N. palea: low concentrations of Pb²⁺ had no effect on the morphology of N. palea, while the high concentration of Pb²⁺ made the living cells’ morphology distortion, the end position of algal cells turned into square from the circular shape, and the cell color deepened which was dark brown.（4）The effect of different concentrations of Pb²⁺ on the movement of N. palea: the low concentration of Pb²⁺ can maintain the velocity of N. palea or even promote the velocity, and the velocity changed rapidly, while the high concentration of Pb²⁺ decreased diatoms’ velocity, even inhibited their movement, and the velocity changed slowly. In each experimental group, the distance moved by diatoms in the culturation of high concentration of Pb²⁺ was less than the control group.