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The Effects of Far‐red Light on Plant Growth and Flavonoid Accumulation in Brassica napus in the Presence of Ultraviolet B Radiation
Author(s) -
Gerhardt Karen E.,
Lampi Mark A.,
Greenberg Bruce M.
Publication year - 2008
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.2008.00362.x
Subject(s) - flavonoid , kaempferol , quercetin , brassica , phytochrome , flavonols , botany , chemistry , cryptochrome , biology , biochemistry , antioxidant , gene , red light , circadian clock
Flavonoid induction is regulated by complex signal transduction pathways involving cryptochrome, phytochrome and UVB photoreceptors. Previously, we identified the UVB‐inducible flavonoids in Brassica napus cv. Topas leaves and showed that UVA affected accumulation of the quercetin (Q) and kaempferol (K) glycosides (Wilson et al. [2000] Photochem. Photobiol . 73, 678–684). In this study, we examined the effects of far‐red light (FR, 700–780 nm) on UVB‐mediated flavonoid accumulation in B. napus . Plants were grown under photosynthetically active radiation (PAR, 400–700 nm, 150 μmol m −2 s −1 ) plus a moderate level of FR (35 μmol m −2 s −1 ) for 14 days, and then transferred to five different irradiation regimes (PAR ± [UVA + UVB] + moderate, intermediate or low fluence FR) for 4 days. Kinetics of flavonoid accumulation were assessed via HPLC. Accumulation of flavonoids, in general, was suppressed by increasing the amount of FR in the spectrum. Furthermore, addition of UVB (290–320 nm) to the spectrum altered the flavonoid composition by causing significant changes in the quantities of individual flavonoids. The relative levels of acylated K glycosides were diminished whereas the relative levels of nonacylated Q glycosides increased dramatically. With UVB exposure there was a five‐fold increase in the Q:K ratio. In contrast, increasing the level of FR in the presence of UVB decreased the Q:K ratio by half.