Chronic exposure to increasing background ozone impairs stomatal functioning in grassland species.

Mills, Gina; Hayes, Felicity; Wilkinson, Sally; Davies, William J.. 2009 Chronic exposure to increasing background ozone impairs stomatal functioning in grassland species. Global Change Biology, 15 (6). 1522-1533.

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Two species found in temperate calcareous and mesotrophic grasslands (Dactylis glomerata and Leontodon hispidus) were exposed to eight ozone treatments spanning preindustrial to post-2100 regimes, and late-season effects on stomatal functioning were investigated. The plants were grown as a mixed community in 14 L containers and were exposed to ozone in ventilated solardomes (dome-shaped greenhouses) for 20 weeks from early May to late September 2007. Ozone exposures were based on O3 concentrations from a nearby upland area, and provided the following seasonal 24 h means: 21.4, 39.9 (simulated ambient), 50.2, 59.4, 74.9, 83.3, 101.3 and 102.5 ppb. In both species, stomatal conductance of undamaged inner canopy leaves developing since a midseason cutback increased linearly with increasing background ozone concentration. Imposition of severe water stress by leaf excision indicated that increasing background ozone concentration decreased the ability of leaves to limit water loss, implying impaired stomatal control. The threshold ozone concentrations for these effects were 15–40 ppb above current ambient in upland UK, and were within the range of ozone concentrations anticipated for much of Europe by the latter part of this century. The potential mechanism behind the impaired stomatal functioning was investigated using a transpiration assay. Unlike for lower ozone treatments, apparently healthy green leaves of L. hispidus that had developed in the 101.3 ppb treatment did not close their stomata in response to 1.5 μm abscisic acid (ABA); indeed stomatal opening initially occurred in this treatment. Thus, ozone appears to be disrupting the ABA-induced signal transduction pathway for stomatal control thereby reducing the ability of plants to respond to drought. These results have potentially wide-reaching implications for the functioning of communities under global warming where periods of soil drying and episodes of high vapour pressure deficit are likely to be more severe.

Item Type: Publication - Article
Digital Object Identifier (DOI):
Programmes: CEH Programmes pre-2009 publications > Biogeochemistry > BG03 Quantifying the growing threat to plant and human health from ground level ozone
UKCEH and CEH Sections/Science Areas: Emmett
ISSN: 1354-1013
Additional Keywords: abscisic acid, Dactylis glomerata, drought tolerance, grassland species, Leontodon hispidus, ozone, rising background, stomata, stomatal conductance
NORA Subject Terms: Agriculture and Soil Science
Ecology and Environment
Date made live: 12 Aug 2009 09:42 +0 (UTC)

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