of foliar flavonoid composition induced by enhanced UV-B radiation in Pinus
ponderosa, Quercus rubra, Pseudotsuga menziesii and Populus
J.H. Bassman1, D.S. Mattinson2, J.K. Fellman2,
G.E. Edwards3, and R. Robberecht4. 2000.
North American Forest Biology Workshop in Merida, Mexico. July 16-20, 2000.
analyses of foliage from several common north temperate tree species
illustrate the species-specific effects of UV-B radiation on both quantity
and composition of foliar flavonoids.
Pinus ponderosa, Quercus rubra and Pseudotsuga
menziesii were field-grown under ambient (1X) and elevated (2X)
biologically effective UV-B radiation (UV-BBE) for Pullman, WA,
USA. A computer-controlled
modulated lamp system was used to supply the supplemental UV-B radiation.
Additionally, Populus tricocarpa was grown in a glasshouse under 0X, 1X and 2X UV-BBE
treatments. Foliage was
harvested seasonally over a three-year period, extracted, purified and
applied to a μBondapak/C18 column HPLC system sampling at
254 nm. Twelve standards were
applied for comparison and several flavonoids were identified; unknown
species are being elucidated via LC-MS.
Higher levels of foliar flavonoids were induced by UV-B radiation
in all species. The two
gymnosperms were less affected by the UV-B treatments than the two
rubra foliage flavonoid concentrations were more than twice that of
any other species, followed by P.
tricocarpa, P. menziesii and
P. ponderosa. Two-year-old
conifer foliage had higher levels of flavonoids than one-year-old tissue.
In addition, the composition of the flavonoids shifted as foliage
aged. Of the 27 flavonoid
peaks found in year-old pine foliage, 18 were higher and 3 were lower in
the 2X treatment as compared to the 1X treatment.
After two years, only 11 of the flavonoid peaks remained elevated
in the 2X treatment, while 7 flavonoids had higher levels in the 1X
treatment. Young tissue of P.
tricocarpa had higher concentrations of flavonoids than more mature
tissue, which also demonstrated reduced treatment effects.
of Natural Resource Sciences, Washington State University, Pullman, WA
of Horticulture and Landscape Architecture, Washington State University,
Pullman, WA 99164-6414 USA
of Botany, Washington State University, Pullman, WA 99164-4238 USA
of Rangeland Ecology, University of Idaho, Moscow, ID 83844-1135 USA