THE INFLUENCE OF ULTRAVIOLET-B LIGHT AND CARBON-DIOXIDE ENRICHMENT ONTHE GROWTH AND PHYSIOLOGY OF SEEDLINGS OF 3 CONIFER SPECIES

Anthropogenic production of CO2 and stratospheric ozone depleting chem icals is altering the plant growth environment. Numerous studies have examined the influence of increasing CO2 and UV-B levels on plant phys iology, but few studies examine their interaction. Jack pine (Pinus ba nksiana Lamb.), black spruce (Picea mariana (Mill.) B.S.P.), and white spruce (Picea glauca (Moench) Voss) were raised in growth rooms from seed for 16 weeks in air with either 350 or 700 mumol.mol-1 of CO2 in the presence or absence of supplemental UV-B irradiation. Classical an d functional growth analyses were performed to identify treatment effe cts. Biomass production in all three species was increased by high CO2 levels while UV-B light reduced it. Shade-intolerant jack pine showed a greater production of UV-B absorbing pigments in UV-B light than di d shade-tolerant spruce species. Overall, white spruce was the most se nsitive species to both treatment factors. The relative magnitude of t he effects in the three species caused by enhanced CO2 and UV-B levels indicate that future conifer seedling growth and competitive ability will be altered by the changing environment.