RESUMEN
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.
Asunto(s)
Antioxidantes/metabolismo , Sequías , Magnoliopsida/fisiología , Hojas de la Planta/metabolismo , Ascorbato Peroxidasas/metabolismo , Ácido Ascórbico/metabolismo , Bulgaria , Deshidratación , Glutatión/metabolismo , Glutatión Reductasa/metabolismo , Glutatión Transferasa/metabolismo , Luz , Estrés Oxidativo , Proteínas de Plantas/metabolismo , Polifenoles/metabolismoRESUMEN
The aim of the present work was to study the response of two sunflower genotypes (cultivated sunflower Helianthus annuus cv. 1114 and newly developed genotype H. annuus × Helianthus argophyllus) to Pb medium-term stress and the role of exogenously applied EDTA in alleviating Pb toxicity in hydroponics. Plant growth, morpho-anatomical characteristics of the leaf tissues, electrolyte leakage, total antioxidant activity, free radical scavenging capacity, total flavonoid content, and superoxide dismutase isoenzyme profile were studied by conventional methods. Differential responses of both genotypes to Pb supplied in the nutrient solution were recorded. Pb treatment induced a decrease in the relative growth rate, disturbance of plasma membrane integrity, and changes in the morpho-anatomical characteristics of the leaf tissues and in the antioxidant capacity, which were more pronounced in the cultivated sunflower H. annuus cv. 1114. The new genotype demonstrated higher tolerance to Pb when compared with the cultivar. This was mainly due to increased photosynthetically active area, maintenance of plasma membrane integrity, permanently high total antioxidant activity, and free radical scavenging capacity as well as total flavonoid content. The addition of EDTA into the nutrient solution led to limitation of the negative impact of Pb ions on the above parameters in both genotypes. This could be related to the reduced content of Pb in the roots, stems, and leaves, suggesting that the presence of EDTA limited the uptake of Pb. The comparative analysis of the responses to Pb treatment showed that the deleterious effect of Pb was more pronounced in the cultivated sunflower H. annuus cv. 1114. The new genotype H. annuus × H. argophyllus was more productive and demonstrated higher tolerance to Pb medium-term stress, which could indicate that it may possess certain mechanisms to tolerate high Pb concentrations. This character could be inherited from the wild parent used in the interspecific hybridization. The ability of EDTA to prevent Pb absorption by the plants could underly the mechanism of limiting of the negative impact of Pb ions. Hence, EDTA cannot be used to enhance Pb absorption from nutrient solution by sunflower plants for phytoremediation purposes.