The influence of ozone on the stomatal and non-stomatal limitation of photosynthesis in Norway spruce, Picea abies (L.) Karst, exposed to soil moisture deficit

Abstract

Summary. Norway spruce, Picea abies (L.) Karst., was exposed to charcoal-filtered air (CF) and non-filtered air + ozone (NF+) and periods of soil moisture deficit from 1985 to 1988 in open-top chambers. Net photosynthesis, stomatal conductance, needle water potential and various shoot properties were measured on 1-year-old shoots during a period of soil moisture deficit. The gas exchange was measured at saturating photosynthetic photon flux density and across a range of CO2 concentrations. The soil moisture deficit induced a mild drought stress in the plants, expressed by a pre-dawn needle water potential of approximately -0.9 MPa and a substantial reduction in net photosynthesis and gas phase conductance. In the CF treatment, intercellular CO2 concentration was reduced, but was unaffected in the NF+ treatment. Furthermore, net photosynthesis declined more in response to the soil moisture deficit in the NF+ treatment than in the CF treatment. This is suggested to be attributed to the carboxylation efficiency at the operating point, which was decreased by 47% and 64% in shoots from the CF and the NF+ treatments, respectively. Stomatal limitation of net photosynthesis was increased by drought by 24-45% in the CF treatment, while it was unaffected in the NF+ treatment. Thus, our results imply that the coupling between the stomatal conductance and the photosynthetic rate was changed and that the marginal cost of water per given amount of carbon gain will increase in trees exposed to ozone, during periods of drought.

Response to three seasons of elevated ozone in the progeny of healthy and unhealthy Norway spruce trees from a plantation with the ‘top dying’ syndrome

“…Hourly averages of ozone exceeded 75 nl l −" in 1989 in the area where the ' top dying ' disease of Norway spruce broke out in Denmark, and even higher levels were observed the year before the disease occurred (Hertel & Hovmand, 1991). Furthermore, elevated levels of ozone have been reported to reduce the ability of Norway spruce to resist water stress (Wallin & Ska$ rby, 1992 ;Mikkelsen & Ro-Poulsen, 1994 ;Ska$ rby et al, 1998).…”

Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Appalachian forest in the USA

“…There is some evidence that high ozone levels can cause stomatal closure and help protect plants from water loss (Tingey & Hogsett, 1985). However, many studies with seedlings and saplings in controlled exposures (Keller & Hasler, 1984; Reich & Lassoie, 1984; Skarby et al ., 1987; Lee et al ., 1990; Wallin & Skarby, 1992; Pearson & Mansfield, 1993; Matyssek et al ., 1995) indicate that, at near‐ambient ozone levels, stomatal control of water loss may be reduced, with stomata responding sluggishly to environmental stimuli including delayed stomatal closure at night.…”

Physiological and biochemical responses of two tree species in urban areas to different air pollution levels

“…The reduced translocation of carbon assimilates to leaves and roots appears to be due to the disruption of carbon partitioning after exposure to air pollution, according to Wallin and Skärby (1992) and Anttonen and Kärenlampi (1996). The thickened cell walls observed for trees in HP sites indicate an increased defense metabolism against air pollution, according to Oksanen et al (2003) and Pääkönen et al (1995).…”