Responses of the Flavonoid Pathway and Antioxidant Ability to UV-B Radiation Stress in Reaumuria soongorica
Reaumuria soongorica is a dwarf shrub mainly found in desert areas of North-west China,and can survive severe environmental stress.Due to the depletion of ozone layer,enhanced UV-B radiation is becoming one most important component of terrestrial radiation that plants are exposed to.This study aimed to assess the responses of the flavonoid pathway and its antioxidant activity to UV-B radiation treatments and its correlation to the lipid peroxide and photosynthetic pigments in R.soongorica leaves.For UV-B treatment,the plants were planted under enhanced UV-B radiation with an intensity of 0.3 mW· cm-2(20％ higher than average natural UV-B radiation dose) at middy by hanging UV-B lamps above the plants.Contents of chlorophyll and carotenoid,levels of lipid peroxidation,activities of flavanone 3-hydroxylase (F3H) and dihydroflavonol 4-reductase (DFR),accumulations of total flavonoids and anthocyanins (ANS) and the scavenging 1,1-Diphenyl-2-picrylhydrazyl radical 2,2 diphenyl-1-(2,4,6-trinitrophenyl) hydrazyl (DPPH) ability and malondialdehyde (MDA) inhibition rate of total flavonoids under different UV-B radiation treatments were investigated.The correlations between key enzymes,products and antioxidant ability of flavonoids in the flavonoid pathway and the lipid peroxide and photosynthetic pigments were also analyzed.The results showed that:The chlorophyll contents decreased and carotenoid content significantly increased with the treatment time increased.The level of MDA increased.The contents of total flavonoids decreased within 4 days and then recovered to the same level as untreatmented.The contents of ANS,DFR activity and ability of scavenging DPPH increased under UV-B stress.The activities of F3H increased within 6 days and then decreased.The flavonoid products ANS,DFR activity and ability of scavenging DPPH and MDA inhibition had significant correlations with MDA level,as well as the photosynthetic pigments contents.Thus,we speculate that under enhanced UV-B radiation,the the flavonoid pathway played important role as antioxidant,and protected the R.soongorica from damaging by UV-B radiation stress.
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