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The response of spring wheat ( Triticum aestivum L.) to ozone at higher elevations
Author(s) -
GRANDJEAN GRIMM A.,
FUHRER J.
Publication year - 1992
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1992.tb01105.x
Subject(s) - photosynthetically active radiation , microclimate , flux (metallurgy) , ozone , vapour pressure deficit , stomatal conductance , environmental science , atmospheric sciences , chemistry , transpiration , canopy , horticulture , botany , photosynthesis , biology , ecology , biochemistry , organic chemistry , geology
summary The flux of O 3 was determined in open‐top chambers (OTC) used to investigate its effect on spring wheat ( Triticum aestivum L., cv. Albis) in 1989 and 1990. The experimental site was located at 900 m above sea level at Zimmerwald, near Bern (Switzerland). The aims were to evaluate the use of OTCs for O 3 flux measurements under field conditions, to assess the role of stomata in controlling the O 3 fluxes, and to establish a quantitative relationship between radiation‐weighted O 3 concentrations and O 3 flux. Measurements were carried out from full expansion of flag leaves until the onset of senescence. Ozone flux was determined by mass balance using the concentrations of O 3 measured at the inlet and outlet of the OTC. The CO 2 exchange rate was corrected for soil‐borne CO O and used as a reference. Measurements of temperature, photosynthetically active radiation (PAR), saturated water vapour pressure deficit (SVPD), and boundary layer conductance were used to describe the microclimate inside OTCs. In the warmer microclimate in 1989, the plant canopy was characterized by a smaller leaf area index (LAI) than in 1990, while the fluxes of O 3 and CO 2 during daytime were generally larger in 1989. The diurnal patterns of fluxes of O 2 and CO 2 , in OTCs supplied with unfiltered air were similar. It is estimated that O 3 absorption via the stomata contributed 50–70% of its total flux. Identical relationships between leaf conductance for O 2 , measured by porometry and leaf conductance calculated from O 3 flux were found in both years, but measured leaf conductance during daytime was generally smaller in 1990 than in 1989. The results indicate that stomatal conductance largely controlled O 3 flux, and that the canopy structure has an influence on the overall conductance of the canopy. Different linear functions were obtained for the relationship between radiation‐weighted O 3 concentration and O 3 flux, using data from OTCs supplied with either charcoal‐filtered air, unfiltered air or unfiltered air enriched with O. (two levels). These relationships form the basis for the calculation of mean O 3 fluxes which can be used as an exposure index in the exposure‐response analysis.