CO2加富对UV-B辐射胁迫下亚心形扁藻光合作用和膜脂过氧化以及抗氧化酶活性的影响

在CO2浓度分别为当今CO2浓度(360 μL/L)和加富浓度(5 000 μL/L)条件下,研究了UV-B胁迫对亚心形扁藻(Platymonas subcordiformis(Wille)Hazen)的光合作用、膜脂过氧化和抗氧化酶活性的影响.实验结果表明:(1)UV-B单独作用下,亚心形扁藻的干重、光合速率、叶绿素a(Chl a)和类胡萝卜素(Car.)含量显著降低,CO2加富单独作用下,亚心形扁藻的干重和光合速率显著升高,叶绿素a和类胡萝卜素含量与对照相比没有显著变化,而UV-B与CO2共同作用则使亚心形扁藻的干重和光合速率与对照相比没有显著变化,叶绿素a和类胡萝卜素含量显著降低.(2)UV-B单独作用和CO2加富单独作用都使可溶性蛋白含量显著降低,UV-B与CO2共同作用下的可溶性蛋白含量比UV-B单独作用的要高.高CO2对藻的可溶性蛋白含量的变化在很大程度上归因于Rubisco蛋白的降低.(3)UV-B单独作用下,O-.2产生速率、H2O2含量和MDA含量显著升高,而CO2加富单独作用下,O-.2产生速率、H2O2含量和MDA含量显著降低,与UV-B单独作用相比,UV-B与CO2共同作用使O-.2产生速率、H2O2含量和MDA含量显著降低.说明CO2加富可以减少活性氧对亚心形扁藻的氧化胁迫,同时减少UV-B对亚心形扁藻的膜脂过氧化伤害.(4)UV-B单独作用下,SOD、POD、CAT、GR和GPx活性显著升高,高CO2单独作用使SOD、POD和GR活性显著降低,而CAT和GPx活性与对照相比稍有所降低,但降低不明显,而UV-B与CO2共同作用则使SOD、POD、CAT、GR和GPx活性比UV-B单独作用少得多.结果表明,高CO2对UV-B胁迫所造成的氧化胁迫具有一定的改善作用,因此CO2浓度升高可能对增强海洋微藻的抗逆能力有利.

Effects of CO2 Enrichment on Photosynthesis,Lipid Peroxidation and Activities of Antioxidative Enzymes of Platymonas subcordiformis Subjected to UV-B Radiation Stress

When the CO₂ concentration was kept at 360 mL/L (ambient) and 5 000 mL/L (elevated), the effects of UV-B stress on photosynthesis, lipid peroxidation and antioxidative enzymes of marine microalgae Platymonas subcordiformis (Wille) Hazen were examined. The experiment indicated that: (1) UV-B alone significantly decreased dry weight, photosynthetic rate, chlorophyll a (Chl a) and carotenoid (Car.) contents; CO₂ enrichment alone enhanced dry weight and photosynthetic rate, but Chl a content and Car. content had no major difference compared with those of ambient UV-B and ambient CO₂; the dry weight and photosynthetic rate of P. subcordiformis grown under the combination of UV-B and CO₂ had no major difference compared with that under ambient UV-B and ambient CO₂; while the Chl a content and Car. content significantly decreased compared to those of P. subcordiformis grown under ambient UV-B and ambient CO₂. (2) Both UV-B alone and CO₂ enrichment alone significantly decreased soluble protein content, when UV-B and CO₂ were in combination, the soluble protein content was higher than that of UV-B alone. Changes in soluble protein content of algae grown in high CO₂ could be largely due to a decline in Rubisco protein. (3) UV-B alone significantly increased the rate of O₂-. production, H₂O₂ and malondialdehyde (MDA) content, CO₂ enrichment alone significantly decreased the rate of O₂-. production, H₂O₂ and MDA contents, when UV-B and CO₂ were in combination, the rate of O₂-. production, H₂O₂ and MDA contents were significantly lower than those of UV-B alone. The results suggested that CO₂ enrichment could reduce oxidative stress of reactive oxygen species to P. subcordiformis, and reduce the lipid peroxidation damage of UV-B to P. subcordiformis. And (4) UV-B alone significantly increased SOD, POD, CAT, GR and GP_X activities, CO₂ enrichment alone significantly decreased the activities of SOD, POD and GR, while the CAT and GP_X activities were decreased a little but not changed significantly compared to ambient UV-B and ambient CO₂. The SOD, POD, CAT, GR and GP_X activities of P. subcordiformis grown under the combination of UV-B and CO₂ were much lower than those of P. subcordiformis grown under UV-B alone. The results indicated that CO₂ enrichment showed a protective effect against the oxidative damage of UV-B-induced stress. Therefore, elevated CO₂ can be favor of enhancing the capacity of stress resistance.