Ameliorating effect of UV‐B radiation on the response of Norway spruce and Scots pine to ambient ozone concentrations

Abstract

Elevated levels of both ozone and UV-B radiation are typical for high-altitude sites. Few studies have investigated their possible interaction on plants. This study reports interactive effects of O3 and UV-B radiation in four-year-old Norway spruce and Scots pine trees. The trees were cultivated in controlled environmental facilities under simulated climatic conditions recorded on Mt Wank, an Alpine mountain in Bavaria, and were exposed for one growing season to simulated ambient or twice-ambient ozone regimes at either near ambient or near zero UV-B radiation levels. Chlorotic mottling and yellowing of current year needles became obvious under twice-ambient O3 in both species at the onset of a high ozone episode in July. Development of chlorotic mottling in relation to accumulated ozone concentrations over a threshold of 40 nL L(exp -1) was more pronounced with near zero rather than ambient UV-B radiation levels. In Norway spruce, photosynthetic parameters at ambient CO2 concentration, measured at the end of the experiment, were reduced in trees cultivated under twice-ambient O3, irrespective of the UV-B treatment. Effects on photosynthetic capacity and carboxylation efficiency were restricted to trees exposed to near zero levels of UV-B radiation, and twice-ambient O3. The data indicate that UV-B radiation, applied together with O3, ameliorates the detrimental effects of O3. The data also demonstrate that foliar symptoms develop more rapidly in Scots pine than in Norway spruce at higher accumulated ozone concentrations

Plant surface reactions: an opportunistic ozone defence mechanism impacting atmospheric chemistry

“…Reactive surface compounds might also contribute to the varying ozone sensitivity of different conifer species (Schnitzler et al, 1999;Landolt et al, 2000) when exposed to the same cumulative ozone concentrations under light conditions. We anticipate therefore that surface ozonolysis plays an important role for the ozone tolerance of certain conifer species, too.…”

The effect of ozone in Scots pine (Pinus sylvestris L.): gene expression, biochemical changes and interactions with UV‐B radiation

“…An alpine climate was simulated in the exposure chambers ( Thiel et al 1996 ) at GSF‐National Research Center for Environment and Health, according to data obtained at the Wank mountain near Garmisch‐Partenkirchen, Germany, at an elevation of 1170 m a.s.l. in the summer of 1990 ( Schnitzler et al 1999 ). Two‐hour means of half‐hourly measurements were used to simulate ambient ozone conditions in the exposure chambers.…”

“…However, little is known about the interaction of elevated ozone concentrations and UV‐B radiation at the molecular level ( Thalmair et al 1996 ; Zinser, Ernst & Sandermann 1998). Furthermore, reports of interactive effects on trees, using simulated outdoor conditions, are likewise rare ( Zeuthen et al 1997 ; Baumbusch et al 1998 ), and it has been shown that UV‐B radiation can ameloriate some detrimental effects of ozone ( Schnitzler et al 1999 ).…”

Seasonal accumulation of ultraviolet‐B screening pigments in needles of Norway spruce (Picea abies (L.) Karst.)

“…Several studies have focused on the effects of UV‐B radiation on coniferous tree species (Krupa & Kickert 1989; Sullivan & Teramura 1992; Schnitzler et al 1999). In Loblolly pine, enhanced UV‐B radiation had minimal effects on different parameters of photosynthesis (stomatal conductance, chlorophyll concentration, or quantum yield efficiency of photosystem II) (Sullivan & Teramura 1992; Naidu et al 1993).…”