The effects of UV-B radiation on some physiological and biochemicalprocesses of DunaliellaSalina, salt waters algae

Faraji, Zahra (2019) The effects of UV-B radiation on some physiological and biochemicalprocesses of DunaliellaSalina, salt waters algae. Masters thesis, University of Mohaghegh Ardabili.

Text پایان نامه نهایی.pdf Download (849kB)

Abstract

Research Aim:The purpose of this study is to investigate the physiological responses of green algae Dunaliella salina to four different doses of UV_B radiation (0.3, 1, 3 and 9 kj/m2), to evaluate the degree of resistance of the above-mentioned algae to this environmental stress. Research methods:100ml of media containing algae is transfered to a 1000ml algoa free media, the new culture medium was cultured in germinator with 16 hours of lighting period, 8 hours of darkness period and a temperature of 15 °C and the light of 6000 Lux. After 40 days, medium was divided into a control group and four experimental groups. Eech group was exposed to a specific level of UV_B. Group I: 0.3, group II: 1 , group III: 3 and group IV 9 kj/m2 respectively. The treatment was repeated 2 days in a row. All the experiments were performed in three replications. Findings:Experimental results showed that UV-B had its effect on photosynthetic parameters such as increase in Fo and carotenoids and decrease in photochemical efficiency of photosystem II,comparison of decrease in chlorophyll a and chlorophyll b showed that the decrease in chlorophyll b was more than chlorophyll a. The Fm also decreased significantly from control to 1 kJ / m2 UV-B treatment and increased significantly in the above treatments (3 and 9 kJ / m 2). On the other hands, evaluation of the results of UV-B-treated biochemical assays resulted in a decrease in total protein content. The content of soluble sugars, total free amino acids and proline content under UV-B treatment showed a significant increaseindicating the mechanisms by which the algae Dunaliella salina cope with stress. Regarding enzymatic activity as the intensity of UV-B stress increased, the catalase activity decreased and ascorbate peroxidase, protease and polyphenol oxidase enzymes significantly increased. The increase in UV-B also caused a significant decrease in the growth and OD of Dunaliella salina algae. Conclusion:Growth and photosynthetic function of Dunaliella algae decreased due to high intensities of UV-B radiation. However, UV-B radiation increased the activity of antioxidant enzymes such as ascorbate peroxidase, protease and polyphenol oxidase, the accumulation of soluble sugars and free amino acids such as proline, as well as the accumulation of carotenoids in the algae Dunaliella salina. This will be accompanied by increased resistance of the algae to oxidative stress and protection of its photosynthetic systems. As a result, Dunaliella salina relatively tolerats high doses of UV-B.

Actions (login required)

View Item