Deschampsia antarctica Desv. is one of two vascular plants that live in the Maritime Antarctic Territory and is exposed to high levels of ultraviolet-B (UVB) radiation. In this work, antioxidant physiology of D. antarctica was studied in response to UVB induced oxidative changes. Samples were collected from Antarctica and maintained in vitro culture during 2 years. Plants were sub-cultured in a hydroponic system and exposed to 21.4 kJ m −2 day −1 , emulating summer Antarctic conditions. Results showed rapid and significant increases in reactive oxygen species (ROS) at 3 h, which rapidly decreased. No dramatic changes were observed in photosynthetic efficiency, chlorophyll content, and level of thiobarbituric acid reactive species (MDA). The enzymatic (superoxide dismutase, SOD and total peroxidases, POD) and non-enzymatic antioxidant activity (total phenolic) increased significantly in response to UVB treatment. These findings suggest that tolerance of D. antarctica to UVB radiation could be attributed to its ability to activate both enzymatic and non-enzymatic antioxidant systems.

Uric acid is the most important non-enzymatic antioxidant present in human saliva. There is a great variability among individuals, both in salivary uric acid content and saliva total reactive antioxidant potential (TRAP). The uric acid present in saliva correlates with plasma uric acid, suggesting that the former is imported from plasma. There are not statistical differences between uric acid or TRAP values in saliva of smokers and nonsmokers. Also, smoking a cigarette does not modify the levels of antioxidants present in saliva.

Background One of the most extreme environments on our planet is the Maritime Antarctic territory, due to its low-water availability, which restricts the development of plants. Sanionia uncinata Hedw. (Amblystegiaceae), the main colonizer of the Maritime Antarctic, has effective mechanisms to tolerate this environment. It has been described that the tolerance to desiccation is mediated by the hormone abscisic acid (ABA), antioxidants systems, accumulation of compatible solutes and proteins of the late embryogenesis abundant (LEA). However, to date, these mechanisms have not been described in S. uncinata . Therefore, in this work, we postulate that the tolerance to desiccation in the Antarctic moss S. uncinata is mediated by the accumulation of ABA, the osmolytes proline and glycine betaine, and dehydrins (an LEA class 11 proteins). To demonstrate our hypothesis, S. uncinata was subjected to desiccation for 24 h (loss in 95% of water content), and the effects on its physiological, photosynthetic, antioxidant and biochemical parameters were determined. Results Our results showed an accumulation of ABA in response to water loss, and the activation of protective responses that involves an increment in levels of proline and glycine betaine, an increment in the activity of antioxidant enzymes such as SOD, CAT, APX and POD, and the accumulation of dehydrins proteins. Conclusion The results showed, suggest that S. uncinata is a  desiccation-tolerant moss, property mediated by high cellular plasticity regulated by ABA.

No abstract

BackgroundIn field, C. quitensis is subjected to many abiotic extreme environmental conditions, such as low temperatures, high UV-B, salinity and reduced water potentials, but not metal or metalloid high concentrations in soil, however, other members of Caryophyllaceae family have tolerance to high concentrations of metals, this is the case of Silene genre. In this work, we hypothesize that C. quitensis have the same mechanisms of Silene to tolerate metals, involving accumulation and induction of antioxidant systems, sugar accumulation and the induction of thiols such as phytochelatins to tolerate.ResultsThe results showing an effective antioxidant defensive machinery involving non-enzymatic antioxidants such as phenolics, GSH and ascorbic acid, in another hand, GSH-related oligomers (phytochelatins) and sugars was induced as a defensive mechanism.ConclusionsColobanthus quitensis exhibits certain mechanisms to tolerate copper in vitro demonstrating its plasticity to tolerate several abiotic stress conditions.