PAR modulation of the UV-dependent levels of flavonoid metabolites in Arabidopsis thaliana (L.) Heynh. leaf rosettes: cumulative effects after a whole vegetative growth period.
Long-term effects of ultraviolet (UV) radiation on flavonoid biosynthesis were investigated in Arabidopsis thaliana using the sun simulators of the Helmholtz Zentrum München. The plants, which are widely used as a model system, were grown (1) at high photosynthetically active radiation (PAR; 1,310 micromol m(-2) s(-1)) and high biologically effective UV irradiation (UV-B(BE) 180 mW m(-2)) during a whole vegetative growth period. Under this irradiation regime, the levels of quercetin products were distinctively elevated with increasing UV-B irradiance. (2) Cultivation at high PAR (1,270 micromol m(-2) s(-1)) and low UV-B (UV-B(BE) 25 mW m(-2)) resulted in somewhat lower levels of quercetin products compared to the high-UV-B(BE) conditions, and only a slight increase with increasing UV-B irradiance was observed. On the other hand, when the plants were grown (3) at low PAR (540 micromol m(-2) s(-1)) and high UV-B (UV-B(BE) 180 mW m(-2)), the accumulation of quercetin products strongly increased from very low levels with increasing amounts of UV-B but the accumulation of kaempferol derivatives and sinapoyl glucose was less pronounced. We conclude (4) that the accumulation of quercetin products triggered by PAR leads to a basic UV protection that is further increased by UV-B radiation. Based on our data, (5) a combined effect of PAR and different spectral sections of UV radiation is satisfactorily described by a biological weighting function, which again emphasizes the additional role of UV-A (315-400 nm) in UV action on A. thaliana.
Götz
Michael
M
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München-German Research Center for Environmental Health, 85764 Neuherberg, Germany.
Albert
Andreas
A
Stich
Susanne
S
Heller
Werner
W
Scherb
Hagen
H
Krins
Andreas
A
Langebartels
Christian
C
Seidlitz
Harald K
HK
Ernst
Dieter
D
D017360:Arabidopsis / Q000033:anatomy & histology / Q000254:growth & development / Q000528:radiation effects; D005419:Flavonoids / Q000378:metabolism*; D044949:Kaempferols / Q000378:metabolism; D010788:Photosynthesis / Q000528:radiation effects; D018515:Plant Leaves / Q000254:growth & development / Q000378:metabolism* / Q000528:radiation effects*; D013995:Time; D014466:Ultraviolet Rays
D005419:Flavonoids; D044949:Kaempferols; C006552:kaempferol