The effects of ultraviolet-B radiation on loblolly pine. I. Growth, photosynthesis and pigment production in greenhouse-grown seedlings

摘要: One-year old loblolly pine (Pinus taeda L.) seedlings were grown in an unshaded greenhouse for 7 months under 4 levels of ultraviolet-B (UV-B) radiation simulating stratospheric ozone reductions 16, 25 and 40% included a control with no UV-B radiation. Periodic measurements made growth gas exchange characteristics needle chlorophyll UV-B-absorbing-compound concentrations. The effectiveness on seedling physiology varied the irradiance level. Seedlings receiving lowest supplemental showed photosynthetic capacity after only 1 month irradiation. These persisted resulted lower biomass production, while increases UV-B-absorbing compounds needles observed. which simulated 25% reduction increase concentrations 6 months, paralleled recovery photosynthesis initial decrease these characteristics. at highest (40% reduction) more rapid concentration effects or until this irradiance. Changes probably result direct light-dependent processes, since observed either stomatal conductance. Further studies are necessary to determine whether responses persist accumulate over subsequent years.