title: Evaluation of radical scavenging system in two microalgae in response to interactive stresses of UV-B radiation and nitrogen starvation.
abstract: The effects of UV-B radiation and/or deprivation of nitrogen stresses on growth rate, some antioxidant compounds, and activities of some antioxidant enzymes, superoxide dismutase (SOD; EC1.15.1.1), ascorbate peroxidase (APx; EC1.11.1.11), guaiacol peroxidase (GUPx; EC1.11.1.7) and glutathione reductase (GR, EC 1.6.4.2), as well as the levels of total glutathione pool, UV-B absorbing pigments, malondialdehyde (MDA) and H2O2concentrations were studied inSpirulina platensisandDunaliella salina.Less damage was observed in response to the combined UV-B and nitrogen deprivation as shown by growth rate and photosynthetic pigments especially inDunaliella salina. A significant increase in flavonoids and phenolics under dual stress was observed. Conversely, a great reduction in malondialdehyde (MDA) and H2O2concentrations were recorded under the combined stress compared to the effect of each stress. Furthermore, a significant increase in GSH/GSSG ratio toward the control was recorded in response to combined stresses, whereas a significant reduction in this ratio was observed in both microalgae in response to each stress. Increased activities of antioxidant enzymes were recorded under UV-B and nitrogen deprivation stresses.
authors.affiliation: King Saud University, Science College, Botany and Microbiology Department, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Al-Rashed
authors.affiliation: King Saud University, Science College, Botany and Microbiology Department, P.O. Box 2455, Riyadh 11451, Saudi Arabia; Alexandria University, Faculty of Science, Botany and Microbiology Department, 21511 Alexandria, Egypt.
authors.forename: Mohamed M
authors.initials: MM
authors.lastname: Ibrahim
authors.affiliation: King Saud University, Science College, Botany and Microbiology Department, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Gehan A
authors.initials: GA
authors.lastname: El-Gaaly
authors.affiliation: King Saud University, Science College, Botany and Microbiology Department, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Sameha
authors.initials: S
authors.lastname: Al-Shehri
authors.affiliation: King Saud University, Science College, Botany and Microbiology Department, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
authors.forename: Ahmed
authors.initials: A
authors.lastname: Mostafa
keywords: Abiotic stresses; Antioxidant enzymes; Dunaliella salina; Oxidative damage; Spirulina platensis