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Maintaining a strong antioxidant system is essential for preventing drought-induced oxidative stress. Thus, in the present study we investigated the role of some non-enzymic and enzymic antioxidants in desiccation tolerance of Haberlea rhodopensis. The effects of high light upon desiccation on antioxidant capacity was estimated by comparing the response of shade and sun plants. The significant enhancement of the antioxidant capacity at 8% RWC corresponded to an enormous increase in flavonoid content. The important role of ascorbate-glutathione cycle in overcoming oxidative stress during drying of H. rhodopensis was established. The antioxidant capacity increased upon dehydration of both shade and sun plants but some differences in non-enzymatic and enzymatic antioxidants were observed. Investigations on the role of polyphenols in desiccation tolerance are scarce. In the present study the polyphenol profiles (fingerprints) of the resurrection plant Haberlea rhodopensis, including all components of the complex are obtained for the first time. It was clarified that the polyphenol complex of H. rhodopensis includes only two types of glycosides - phenylethanoid glucosides and hispidulin 8-C-glucosides. Upon desiccation the polyphenol content increase and the main role of phenylethanoid glucosides in the protection of H. rhodopensis was revealed., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Sunflower plants (Helianthus annuus L.) cv. 1114 were used as test plants to investigate the combined toxicity effect of heavy metals present in soils collected from three different locations of a polluted area near a non-ferrous metal smelter. Soils were designated as highly contaminated, moderately contaminated and non-contaminated (control) based on the content analysis of soil samples. The photosynthetic performance was assessed by the changes in the functional activity of PS1 (photosystem 1) and PS2 (photosystem 2). Evidence for accelerated electron flow beyond the first qiunone acceptors in PS2 (QA) but not related with accelerated reduction of the first acceptor of light in PS1 (P700) is presented. The retarded rate of the slower (IDP) increase of the rapid phase of Kautsky effect (OIDP) as well as the lower level of QB-nonreducing PS2 reaction centers in HCS plants suggested an accelerated rate of electron flow in the PS2 acceptor side. The response of the antioxidant defense system included enhancement of superoxide dismutase (SOD) activity, total antioxidant activity and content of flavonoids. Changes in thylakoid electron transport chain reactions accompanied with altered oxidative stress-related metabolic activity could be considered as a protective mechanism operating in conditions of combined heavy metal toxicity. [ABSTRACT FROM AUTHOR]