The effects of far-red light on plant growth and flavonoid accumulation in Brassica napus in the presence of ultraviolet B radiation.
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 micromol m(-2) s(-1)) plus a moderate level of FR (35 micromol 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.
Gerhardt
Karen E
KE
Department of Biology, University of Waterloo, Waterloo, ON, Canada.
Lampi
Mark A
MA
Greenberg
Bruce M
BM
D029688:Brassica napus / Q000737:chemistry / Q000254:growth & development* / Q000378:metabolism* / Q000528:radiation effects; D002851:Chromatography, High Pressure Liquid; D005419:Flavonoids / Q000737:chemistry / Q000378:metabolism*; D007700:Kinetics; D015394:Molecular Structure; D018515:Plant Leaves / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects; D013050:Spectrometry, Fluorescence; D013379:Substrate Specificity; D014466:Ultraviolet Rays
D005419:Flavonoids