The stomatal conductance (
gs) of rice leaves in vertical canopy layers was measured in both the ambient and FACE fields, where the concentration of ozone ([O
3]) was elevated artificially, during the heading and flowering stages, 2007. The
gs sub-model of rice was developed by a multiplicative approach with modifications of PAR, VPD, AOT40 and [O
3], while the multi-layer model of the O
3 uptake process in the rice canopy was developed by incorporating the
gs sub-model.
By the proposed model, vertical profiles of O
3 fluxes on a single leaf (
FO3) and in each canopy layer were calculated in the conditions 46.0, 40.2 and 43.6 ppb of [O
3] at
z = 280 cm at 1030, 1200 and 1530 h on August 30. O
3 uptake by a single leaf (-
FO3) in the upper canopy layer peaked at 1530 h and was smallest at 1200 h. The smallest -
FO3 at 1200 h was caused not only by the lowest [O
3] but also smaller
gs, while the smaller
gs at 1200 h was caused by smaller PAR on the flag leaf, even under the largest global solar radiation (SR) condition, because the leaf stands erect. The estimated O
3 uptakes in the paddy field were 14.9, 13.7 and 12.1 (nmol m
-2 s
-1) at 1030, 1200 and 1530 h, respectively.
The predicted
FO3 under different [O
3] conditions by the model revealed that
FO3 would exceed the threshold of -6 nmol m
-2 s
-1 in more than 60 ppb [O
3] at 1030 and 1200 h and in more than 50 ppb at 1530 h. The predicted
FO3 under different SR conditions with fixed [O
3] of 80 ppb revealed that
FO3 would reach the threshold in more than 400 W m
-2 of SR at 1030 and 1200 h and more than 200 W m
-2 at 1530 h under this relatively high [O
3] condition.
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