Study On Effects Of Compensation In Pavlova Viridis Under UV-B Stress

In order to characterize the compensation and overcompensation mechanism of microalgae, as well as the bioactive substances variation during the compensation process, effects of UV-B stress on Pavlova viridis was studied, 4 treatment groups were set up for this study. The group â… (10min radiation) and group â…¡(15min radiation) had 5 different radiation levels, which were 4, 6, 8, 10, and 12μw·cm^-2 respectively. Group â…¢ was radiated under 2μw·cm^-2 UV-B for 15, 30, and 45min respectively. Group â…£ was radiated under 12μw·cm^-2 UV-B for 9, 12, 15, and 18min respectively. And also set up the control. After the radiation, all treatments were incubated for another 12 days, and the biomass, OD, concentrations of chlorophyll a, carotenoid, cellular protein, and carbohydrate were measured, meanwhile, some other correlative parameters were calculated and compared. The results show that UV-B stress significantly inhibited (P<0.05) the growth of P.viridis. The inhibition effect increased with the radiation intensity and duration. The growth compensation was also observed after the UV-B stress, and the parameters of OD, average relative growth rate and biomass were all significantly higher than the control's. The highest OD and biomass increase were 26.55% and 29.87% of the control. P.viridis did not show the irreversible damage under all UV-B stress conditions in this study, and the content of chlorophyll a, carotenoid, cellular protein and carbohydrate were all higher than control treatment during the compensation process, the highest increase were 1.29, 1.29, 1.15, and 1.34 times of control. However, the lag time for the compensation growth occurred 3⁵ days after UV-B radiation and it increased with the radiation intensity and duration. There was no lag phase under 4 or 6μw·cm^-2 radiation for 15 min, while 3 days under 8 or 10μw·cm^-2 radiation, 5 days under 12μw·cm^-2 radiation. When the radiation intensity was 12μw·cm^-2, the lag phase was 3 days when the radiation duration was 9 or 12min, while 5 days when radiation duration was 15min, 9 days when radiation duration was 18min. Overall, this study showed that the compensation growth of P.viridis after UV-B stress could increase thecellular contents of carotenoid, protein, and carbohydrate, which provided the valuable information for bioactive substances production.