Search

Plants have evolved mechanisms to avoid and repair UV radiation damage; it is not surprising that photomorphogenic responses to UV-B and UV-C are often assumed to be adaptations to harmful radiation. Free radicals generated by UV are likely to be involved in the induction of antioxidant defence system. In this study plants were grown for 5 weeks in controlled conditions. Plants were grown in vermiculite medium before applying the UV treatments, and irrigated daily by Hoagland solution for 5 weeks. After 5 weeks, plants were exposed to UV-A (320-390 nm), UV-B (312 nm), and UV-C (254 nm) irradiation with a density of 6.1 (Wm-2), 5.8 (Wm-2) and 5.7 (Wm-2) for 2 weeks. Each plant was exposed to UV in their light period for 27 min per day for 14 days. In each experiment 4 replicates were used. Data were analyzed using SPSS software, and averages were compared by Duncan's test. Activity of antioxidant enzymes could be found in the plant antioxidant defence system. The activity of antioxidant enzymes (namely, peroxidase, polyphenol oxidase, ascorbate peroxidase, catalase, and glutathione reductase) enhanced in leaves and roots of pepper plants in response to UV-B and UV-C radiation. The increase in the activity of antioxidant enzymes could minimise the effects of ultraviolet radiation. UV treatments induced significant increase in ascorbic acid in leaf and root of exposed plants. The present study was conducted to determine the role of antioxidant defence mechanism in UV-A, UV-B and UV-C treated plants of Capsicum annuum L. [ABSTRACT FROM AUTHOR]

Although ultraviolet radiation is potentially harmful, it is an important component of terrestrial radiation to which plants have been exposed since invading land. Since then, plants have evolved mechanisms to avoid and repair UV radiation damage. Therefore, it is not surprising that photomorphogenic responses to UV-B and UV-C are often assumed to be adaptations to harmful radiation. Most of the compounds accumulated are directly involved in UV-B and UV-C protection: they are either efficient in filtering excess radiation or in scavenging radicals. In this study plants were grown for 5 weeks in controlled environment room. The plants were grown in vermiculite medium using pots. Before UV treatments, plants were irrigated with nutrient solution (Hoagland solution) for 5 weeks. Then plants were exposed to UV-A (320-390 nm), UV-B (312 nm) and UV-C (254 nm) irradiation with a density of 6.1 (Wm-2), 5.8 (Wm-2) and 5.7 (Wm-2) for 2 weeks. Plants were treated with UV in their light period for 27 min per day for 14 days. The influence of UV-A, UV-B and UV-C radiation on chlorophyll, flavonoids, anthocyanin, proline, membrane permeability, lipid peroxidation and UV-absorbing compound was examined. Results showed that the contents of chlorophyll a, b and carotenoids of pepper leaves were reduced significantly in those plants which were exposed to UV-B and UV-C radiation and compared with control and UV-A treated plants. In contrast, UV-B and UV-C increased (P < 0.05) proline, quercetin, rutin and anthocyanin concentrations in leaves of Capsicum annuum L. Ultraviolet radiation induced oxidative stress in pepper by increasing lipid peroxidation and membrane permeability which indicating that limits of tolerance are much less than damaged caused by UV-radiation. [ABSTRACT FROM AUTHOR]