Nighttime exposure to ozone reduces whole-plant production in Betula pendula

Abstract

For 20 weeks during the growing season, cuttings of one birch clone (Betula pendula Roth.) were exposed in the Birmensdorf fumigation chambers to O(3)-free air (control) or 75 nl O(3) l(-1). Ozone was supplied either from 1900 until 0700 h (nighttime regime), from 0700 until 1900 h (daylight regime), or all day (24-h regime). By autumn, reductions in whole-plant biomass production, root/shoot biomass and stem weight/length ratios were evident in all three O(3) regimes. The reductions in cuttings receiving the 24-h O(3) treatment were about twofold larger than in cuttings receiving the daylight O(3) treatment. Stomata were open at night, and stomatal conductance was about 50% of its maximum daytime value. We calculated that the rate of O(3) uptake into leaves in the dark approached 4 nmol m(-2) s(-1). Whole-plant production and carbon allocation were more sensitive to O(3) during the night than during the day; however, O(3) exposure caused similar visible leaf injury in both of the 12-h regimes, although the leaves exposed to O(3) at night exhibited delayed O(3)-induced shedding. Overall, changes in production and carbon allocation were determined by the external O(3) dose rather than by the kind of O(3) exposure, indicating that, at the seasonal scale, the internal dose of ozone that was physiologically effective was a constant fraction of the external O(3) dose. We conclude that nighttime O(3) exposures should be included in the daily time period for determining critical concentrations of O(3) causing injury in trees.

Carbon flux to woody tissues in a beech/spruce forest during summer and in response to chronic O<sub>3</sub> exposure

“…At the same time, the rate of stem CO 2 efflux was significantly increased under 2 × O 3 . Such a stimulation following O 3 exposure has been reported in several studies on herbaceous plants (Grantz and Shrestha, 2006;Reiling and Davison, 1992) and is known to sustain repair-and detoxification processes (Matyssek et al, 1995;Rennenberg et al, 1996). The slightly increased C allocation to such processes in spruce may relate to its overall lower O 3 sensitivity compared to beech (Kozovits et al, 2005a, b;Matyssek et al, 2010b;Pretzsch et al, 2010).…”

Foliage surface ozone deposition: a role for surface moisture?

“…These and other studies are based on estimation of g sto,wv from field water vapour exchange measurements during night, which are technically demanding (small fluxes close to detection limit) and uncertain. In addition, in order not to change the stomatal behaviour, the ambient temperature and RH are tracked inside the gas exchange enclosure (Matyssek et al, 1995;Snyder et al, 2003) and thus the potential film formation is not precluded. In our study, nocturnal water vapour flux measurement was discarded due to high RH interfering with the enclosure materials but we measured increase in the SW signal that we attributed to water film formation on the foliage surface.…”

Interactions of chronic exposure to elevated CO2 and O3 levels in the photosynthetic light and dark reactions of European beech (Fagus sylvatica)

“…Plant sensitivity to ozone has often been found to relate to the stomatal conductance, as high O $ influx through the stomata may increase the risk of injury (Reich, 1987 ;Barnes & Wellburn, 1998 ;Volin et al, 1998). Although both elevated CO # and chronic O $ exposure have the potential of reducing stomatal aperture (Ceulemans & Mousseau, 1994 ;Matyssek et al, 1995), interactions on and, thus, impact of O $ uptake, have rarely been investigated with respect to broad-leaf trees.…”