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Effects of elevated O 3 and CO 2 concentrations on photosynthesis and stomatal conductance in Scots pine
Author(s) -
KELLOMäKI S.,
WANG K.Y.
Publication year - 1997
Publication title -
plant, cell and environment
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.646
H-Index - 200
eISSN - 1365-3040
pISSN - 0140-7791
DOI - 10.1111/j.1365-3040.1997.tb00676.x
Subject(s) - stomatal conductance , scots pine , photosynthesis , shoot , horticulture , conductance , vapour pressure deficit , botany , chemistry , carboxylation , respiration rate , respiration , zoology , pinus <genus> , biology , transpiration , mathematics , biochemistry , combinatorics , catalysis
Naturally regenerated Scots pines ( Pinus sylvestris L.), aged 28–30 years old, were grown in open‐top chambers and subjected in situ to three ozone (O 3 ) regimes, two concentrations of CO 2 , and a combination of O 3 and CO 2 treatments From 15 April to 15 September for two growing seasons (1994 and 1995). The gas exchanges of current‐year and 1‐year‐old shoots were measured, along with the nitrogen content of needles. In order to investigate the factors underlying modifications in photosynthesis, five parameters linked to photosynthetic performance and three to stomatal conductance were determined. Elevated O 3 concentrations led to a significant decline in the CO 2 compensation point (Г * ), maximum RuP 2 ‐saturated rate of carboxylation ( V cmax ), maximum rate of electron transport ( J max ), maximum stomatal conductance ( g smax ), and sensitivity of stomatal conductance to changes in leaf‐to‐air vapour pressure difference (∂ g s /∂ D v ) in both shoot‐age classes. However, the effect of elevated O 3 concentrations on the respiration rate in light ( R d ) was dependent on shoot age. Elevated CO 2 (700 μmol mol −1 ) significantly decreased J max and g smax but increased R d in 1‐year‐old shoots and the ∂ g s /∂ D v in both shoot‐age classes. The interactive effects of O 3 and CO 2 on some key parameters (e.g. V cmax and J max ) were significant. This may be closely related to regulation of the maximum stomatal conductance and stomatal sensitivity induced by elevated CO 2 . As a consequence, the injury induced by O 3 was reduced through decreased ozone uptake in 1‐year‐old shoots, but not in the current‐year shoots. Compared to ambient O 3 concentration, reduced O 3 concentrations (charcoal‐filtered air) did not lead to significant changes in any of the measured parameters. Compared to the control treatment, calculations showed that elevated O 3 concentrations decreased the apparent quantum yield by 15% and by 18%, and the maximum rate of photosynthesis by 21% and by 29% in the current‐year and 1‐year‐old shoots, respectively. Changes in the nitrogen content of needles resulting from the various treatments were associated with modifications in photosynthetic components.