Primary Study Of Effects Of UV-B Radiation On Cytology And Physiology In Marine Microalgae

Under experimental condition, we simulate the process of enhanced UV-B irradiation on marine microalgae. The physiological and biochemical responses of enhanced UV-B irradiation on marine microalgae and the changes of ultrastructure of Platymanas subcordiformis using biochemical methods and transmission electron microscopy, in order to provide theory basis for the mechanisms of UV-B irradiation on marine microalgae. Through experiment, we obtain the following results:1. Through the experiment of biochemical response of UV-B irradiation on marine microalgae, we got the following conclusions: (1) UV-B irradiation can inhibit the growth and photosynthetic rate of Nitzschia closterium, and the inhibiting effects was more significant when the time was prolonged. (2) UV-B irradiation decreased soluble sugar. In the initial 2 days, soluble sugar of Nitzschia closterium decreased rapidly, the soluble sugar on the 4th day has no major change compared with the soluble sugar on the 2nd day, on the 6th day, the soluble sugar decreased again. (3) the protein content of UV-B treated group significantly increased on the 2nd day, rapidly decreased subsequently; (4) GSH content of control group increased as time prolonged, the GSH content on the 2nd day has no major change with initial time (0 d), after the 2nd day, the GSH content decreased rapidly; (5) POD activity of control group increased as time prolonged, the POD activity on the 2nd day increased significantly compared with POD activity on the initial time (0 d), after the 2nd day, POD activity rapidly decreased as time prolonged.2. From the changes of enhanced UV-B radiation on the ultrastructure of Platymanas subcordiformis, we obtain the conclusion that (1) the chloroplast structure changed significantly. The thylakoid of chloroplast was lost, the chloroplast was shrinked and composed into several discontinuous parts, which suggest that the function of chloroplast was destroyed; (2) the cell wall was thickened clearly,plasmolysis was found in most of Platymanas subcordiformis cells; (3) the number of mitochondria increased, some cristae of mitochondria were dissolved; (4) the number of vacuolar increased and the size of vacuolar was not uniform, the shape was deformed; (5) the nucleus was deformed and part of the nucleus membrane was dissolved; (6) Golgi dicytosomes accompanied with a loose arrangement of cisternae and the peripheral tips of the dictyosome cisternae are not especially swollen.3.The study of POD isozyme zymogram of Chlorella. sp indicated that the POD activity decreased after irradiated by UV-B, at the same time, POD isozyme lost the enzymatic strips of Rf=0.469 and 0.864, after UV-B irradiation .4. The protein composition between the control group and treated group of Platymanas sp. using the method of native polyacrylamide gel eletrophoresis (PAGE) indicated that, in the Platymanas sp. protein, content of molecule of polypeptide more than 14.4kD is a little more than that of molecule of polypeptide less than 14.4RD. The eletrophoresis strip of UV-B treated group was dyed deeper than control group, which suggested that UV-B radiation increased soluble protein of Platymanas sp.