The Effects of Ultraviolet Radiation on the Contents of Chlorophyll, Flavonoid, Anthocyanin and Proline in Capsicum annuum L

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), 5.8 (Wm) and 5.7 (Wm) 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 UVradiation.