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Jung S, Kim JS, Cho KY, Tae GS, Kang BG: Antioxidant responses of cucumber (Cucumis sativus) to photoinhibition and oxidative stress induced by norflurazon under high and low PPFDs. Plant Sci. 2000 Apr 25;153(2):145-154.
Photooxidative damage is exacerbated by norflurazon (NF), which blocks carotenoid biosynthesis. This study examined the influence of photosynthetic photon flux density (PPFD) on the overall responses of both non-enzymatic and enzymatic antioxidants to NF-caused oxidative damage in leaves of cucumber (Cucumis sativus). Seven-day-old cucumber plants were exposed to NF under either low PPFD (30 micromol m (-2) s (-1)) or high PPFD (300 micromol m (-2) s (-1)) for 3 days. The NF plants exposed at high PPFD had lower levels of F (v)/F (m) ratio, quantum yield of electron transport, and 33-kDa protein of photosystem II as compared with the NF plants at low PPFD. In the NF plants, there was a reduction in total chlorophylls and carotenoids except newly formed zeaxanthin in either PPFD. The NF plants at high PPFD resulted in less level of photochemical quenching, q (P), and Stern-Volmer quenching, NPQ, than those of the plants at low PPFD, whereas both plants had similar level of non-photochemical quenching coefficient, q (N). However, the level of PPFD did not significantly affect the NF-caused induction of antioxidant enzymes including peroxidase, superoxide dismutase, glutathione reductase, and ascorbate peroxidase. |
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