title: UV-B response of greening barley seedlings.
abstract: The relationship between the greening stage of barley seedlings and their response to UV-B irradiation was studied. Etiolated barley seedlings ( Hordeum vulgare L., cv. Alfa) greened 12, 24 and 48 h were exposed to UV-B irradiation (312 nm) for 5 h. As a result of UV-B treatment the rate of CO(2) fixation and chlorophyll contents decreased but flavonoids, UV-B-induced compounds and carotenoids increased. The inhibition of photosynthesis in green plants was lower in comparison to greening ones. The 12 h greening plants were more sensitive to UV-B treatment than the plants greening 24 h and particularly 48 h, estimated by the quantum efficiency of PSII photochemistry and the oxygen production rate. The levels of flavonoids and UV-B induced compounds enhanced with increasing the greening time. Activity of antioxidant enzymes catalase, peroxidase and superoxide dismutase increased during the seedlings greening and as a result of UV-B irradiation, but the pattern of isoforms remained similar to those found in the controls. UV-B preferentially induced Cu,Zn-superoxide dismutase. Increase of UVB induced synthesis of antioxidant enzymes is in line with their important role in the plant response to UV-B stress. Data presented show that the response of barley seedlings to UV-B irradiation is related to the development stage of photosynthetic apparatus.
authors: Department Plant Stress Molecular Biology, Academic Metodi Popov Institute of Plant Physiology, Bulgarian Academy of Sciences Academic Georgi Bonchev Street, Building 21, Sofia 1113, Bulgaria. fedina@obzor.bio21.bas.bg
authors: Ivanka
authors: I
authors: Fedina
authors: Maya
authors: M
authors: Velitchkova
authors: Katya
authors: K
authors: Georgieva
authors: Dimitrina
authors: D
authors: Nedeva
authors: H
authors: H
authors: Çakirlar
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D002374:Catalase / Q000737:chemistry; D002734:Chlorophyll / Q000737:chemistry; D005419:Flavonoids / Q000737:chemistry; D001467:Hordeum / Q000378:metabolism* / Q000528:radiation effects*; D006861:Hydrogen Peroxide / Q000737:chemistry; D008315:Malondialdehyde / Q000737:chemistry; D008856:Microscopy, Fluorescence / Q000379:methods; D010100:Oxygen / Q000737:chemistry; D009195:Peroxidase / Q000737:chemistry; D010777:Photochemistry / Q000379:methods; D010936:Plant Extracts / Q000378:metabolism; D012639:Seeds / Q000378:metabolism / Q000528:radiation effects*; D013482:Superoxide Dismutase / Q000737:chemistry; D013997:Time Factors; D014466:Ultraviolet Rays
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D010936:Plant Extracts; D002734:Chlorophyll; D008315:Malondialdehyde; D006861:Hydrogen Peroxide; D002374:Catalase; D009195:Peroxidase; D013482:Superoxide Dismutase; D010100:Oxygen