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The main goal of this study was to obtain detailed information on photosynthetic responses of evergreen broad-leaved tree species to ozone (O3). For this, two-year-old seedlings of Castanopsis sieboldii, Quercus glauca, and Q. myrsinaefolia were grown for one growing season, from 15 May to 27 October 2014 under three levels of gas treatments, charcoal-filtered air and 1.0 time and 1.5 times ambient O3 concentrations. We analysed the intercellular CO2 concentration-response curve of the net photosynthetic rate, i.e., the A/Ci curve, in July and October, and growth measurement was carried out at the end of the experiment in October. We observed a difference in O3 susceptibility among the species. Negative effects of O3 were observed on the growth and photosynthetic traits of C. sieboldii, while no significant effects on these traits were noted in the two Quercus species. The decrease in light-saturated net photosynthetic rate (Asat) of C. sieboldii under elevated O3 was accompanied with a significant decrease in the maximum rate of carboxylation (Vcmax). Decreases of leaf nitrogen content and nitrogen use efficiency to Rubisco are considered as factors contributing to lower Vcmax in C. sieboldii seedlings under elevated O3. In addition to the decrease in Vcmax, O3 exposure induced marginal increase of stomatal limitation of photosynthesis. These results indicate that both biochemical and diffusion processes in photosynthesis are responsible for the decrease in Asat of C. sieboldii under elevated O3.

Leaf ozone uptake through the stomata is an important index for the ozone risk assessments on trees. Stomatal conductance (g s ) and ozone concentration ([O 3 ]), determinants of the leaf ozone uptake, are known to show vertical gradients within a tree canopy. However, less is known about the within-canopy vertical gradient of leaf ozone uptake. This study was aimed to elucidate how the vertical gradient of [O 3 ] and g s affect needle ozone uptake within a canopy of mature Cryptomeria japonica trees in a suburban forest at Tokyo, Japan. For this purpose, a multilayer gas exchange model was applied to estimate the vertical gradient of needle g s and the accumulated ozone uptake during the study period (POD 1 , Phytotoxic Ozone Dose above a threshold of 1 nmol m -2 s -1 ). In addition, we also tested several scenarios of vertical gradient of [O 3 ] within the canopy for sensitivity analysis. The POD 1 was declined from the top to the bottom of the canopy. This tendency strongly depended on the vertical gradient of g s and was hardly affected by the changes in simulated vertical reductions of the [O 3 ]. We further assessed the photosynthesis of sunlit needles (needles absorbing both direct and diffuse light) and shaded needles (needles only absorbing diffuse light). The photosynthesis of shaded needles in the upper half of the canopy made a great contribution to the entire canopy photosynthesis. In addition, given that their POD 1 was lower than that of sunlit needles, ozone may affect sunlit and shaded needles differently. We concluded that these considerations should be incorporated into modeling of the calculation of ozone uptake for mature trees to make accurate predictions of the ozone effects on trees at the canopy scale., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Ozone uptake through the stomata in tree leaves is an important process for improving air quality by urban trees. Stomatal conductance (g s ) is a key determinant of stomatal ozone uptake. The parameterization of g s models for estimating stomatal ozone uptake of trees has mainly been carried out using g s data measured in seedling leaves although the leaf traits may differ between mature trees and seedlings. In the present study, we compared stomatal ozone uptake estimated by g s models parameterised with data from mature trees and seedlings of Zelkova serrata. We measured g s in leaves of mature trees and seedlings of Z. serrata using a leaf porometer for 3-4 growing seasons. The Jarvis-type g s model was parameterised with data from mature trees and seedlings, separately. The maximum g s , and the functions of the seedling g s estimation model regarding the response to air temperature, vapour pressure deficit and atmospheric ozone concentration were the factors inducing lower stomatal ozone uptake. In contrast, the function of the seedling g s estimation model regarding the response to irradiance resulted in a higher estimated stomatal ozone uptake. The estimated stomatal ozone uptake for one growing season (April-September) by the seedling g s estimation model was 27% lower than that by the mature tree g s estimation model. These results indicate that leaf gas exchange traits of Z. serrata were different between mature trees and seedlings, and that estimating ozone uptake in mature tree leaves using a model based on seedling g s measurements results in an underestimation., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Ozone (O 3 ) is a phytotoxic air pollutant, the adverse effects of which on growth and photosynthesis are modified by other environmental factors. In this study, we examined the combined effects of O 3 , elevated CO 2 , and soil nitrogen supply on Siebold's beech seedlings. Seedlings were grown under combinations of two levels of O 3 (low and two times ambient O 3 concentration), two levels of CO 2 (ambient and 700 ppm), and three levels of soil nitrogen supply (0, 50, and 100 kg N ha -1 year -1 ) during two growing seasons (2019 and 2020), with leaf photosynthetic traits being determined during the second season. We found that elevated CO 2 ameliorated O 3 -induced reductions in photosynthetic activity, whereas the negative effects of O 3 on photosynthetic traits were enhanced by soil nitrogen supply. We observed three-factor interactions in photosynthetic traits, with the ameliorative effects of elevated CO 2 on O 3 -induced reductions in the maximum rate of carboxylation being more pronounced under high than under low soil nitrogen conditions in July. In contrast, elevated CO 2 -induced amelioration of the effects of O 3 on stomatal function-related traits was more pronounced under low soil nitrogen conditions. Although we observed several two- or three-factor interactions of gas and soil treatments with respect to leaf photosynthetic traits, the shoot to root dry mass (S/R) ratio was the only parameter for which a significant interaction was detected among seedling growth parameters. O 3 caused a significant increase in S/R under ambient CO 2 conditions, whereas no similar effects were observed under elevated CO 2 conditions. Collectively, our findings reveal the complex interactive effects of elevated CO 2 and soil nitrogen supply on the detrimental effects of O 3 on leaf photosynthetic traits, and highlight the importance of taking into consideration differences between the responses of CO 2 uptake and growth to these three environmental factors., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The hypothesis of the present study is that not only distributions of leaf photosynthetic traits and shoot growth along light gradient within a canopy of forest trees, but also that of leaf anti-herbivory defence capacities are influenced by soil nutrient condition. To test this hypothesis, we investigated the distributions of photosynthetic traits, shoot growth, anti-herbivory defence and leaf herbivory rate throughout the canopy of Quercus serrata grown in two sites with different soil nutrient conditions. In both sites, photosynthetic traits, shoot growth, and anti-herbivory defence were greater in the upper canopy. The overall defence and herbivory rate in the lower nutrient condition were higher and lower than those in the higher nutrient condition, respectively. Although differences in leaf traits between upper and lower canopies in the higher nutrient condition were smaller than those in the lower nutrient condition, no difference was found for anti-herbivory defence. These results suggest that soil nutrient condition does not affect the distributions of leaf anti herbivory defence along light gradient within a canopy of Q. serrata., (© 2021. The Author(s).)

We aimed to clarify the effects of ozone (O 3 ) on photosynthetic ability of upper and lower canopy leaves of Fagus crenata Blume seedlings grown under different soil nutrient conditions. To accomplish this objective, we analyzed the response of photosynthetic parameters such as maximum carboxylation rate (V cmax ) to cumulative stomatal O 3 uptake (ΣF st ) and reduction rate of V cmax per unit ΣF st as an index of detoxification capacity for O 3 . The seedlings of Fagus crenata were grown for two growing seasons (2014-2015) in nine treatments comprised of a combination of three levels of gas treatments (charcoal-filtered air or 1.0- or 1.5-times ambient O 3 concentration) and three levels of soil nutrient treatments (non-fertilized or a supply of relatively low or high concentrations of compound fertilizer). The nutrient supply significantly increased the degree of O 3 -induced reduction in V cmax in September. However, nutrient supply did not significantly increase ΣF st and reduce the detoxification capacity for O 3 . On the other hand, the degree of O 3 -induced reduction in V cmax of upper canopy leaves was higher as compared with that of lower canopy leaves in August due to the higher ΣF st . However, the reduction rate of V cmax per unit ΣF st in lower canopy leaves was higher than that in upper canopy leaves, indicating lower detoxification capacity for O 3 in lower canopy leaves. Reduction rate of V cmax per unit ΣF st over the threshold, which is assumed to be proportional to gross photosynthetic rate, was similar between upper and lower canopy leaves. Therefore, capacity of photosynthetic CO 2 assimilation is likely to be associated with detoxification capacity for O 3 in upper and lower canopy leaves of F. crenata seedlings grown under different soil nutrient conditions., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Ground-level ozone (O3) concentrations are expected to increase over the 21(st) century, especially in East Asia. However, the impact of O3 has not been directly assessed at the forest level in this region. We performed O3 flux-based risk assessments of carbon sequestration capacity in an old cool temperate deciduous forest, consisting of O3-sensitive Japanese beech (Fagus crenata), and in a warm temperate deciduous and evergreen forest dominated by O3-tolerant Konara oak (Quercus serrata) based on long-term CO2 flux observations. On the basis of a practical approach for a continuous estimation of canopy-level stomatal conductance (Gs), higher phytotoxic ozone dose above a threshold of 0 uptake (POD0) with higher Gs was observed in the beech forest than that in the oak forest. Light-saturated gross primary production, as a measure of carbon sequestration capacity of forest ecosystem, declined earlier in the late growth season with increasing POD0, suggesting an earlier autumn senescence, especially in the O3-sensitive beech forest, but not in the O3-tolerant oak forest.

To assess the effects of O(3)on growth, net photosynthesis and yield of two African varieties of cowpea(Vigna unguiculata L.), Blackeye and Asontem were exposed as potted plants to air that was either filtered to remove O(3) (FA), non-filtered air (NF), non-filtered with added O3 of approximately 50 nL L(-1) (ppb) from 11:00 to 16:00 (NF + O(3)) for 88 days in open-top chambers. The mean O(3) concentration (11:00-16:00) during the exposure period had a range from 16 ppb in the FA treatment to 118 ppb in the NF + O(3) treatment. Net photosynthetic rate and leaf area per plant were significantly reduced by exposure to O(3), reducing the growth of both varieties. Exposure to O(3) significantly reduced the 100-seed weight and number of seeds per pod. As a result, cowpea yield was significantly reduced by long-term exposure to O(3), with no difference in sensitivity between the varieties.

To construct stomatal conductance models and estimate stomatal O3 uptake for Fagus crenata, Quercus serrata, Quercus mongolica var. crispula and Betula platyphylla, stomatal conductance (gs) was measured in seedlings of the four tree species. Better estimates of gs were made by incorporating the acute effects of O3 on gs into the models and the models could explain 34-52% of the variability in gs. Although the O3 concentration was relatively high in spring from April to May, COU of F. crenata, Q. serrata and Q. mongolica var. crispula were relatively low and the ratios of COU in spring to total COU in one year were 16.8% in all tree species because of low gs limited mainly by leaf pre-maturation and/or low temperature. The COU of B. platyphylla were relatively high mainly because of rapid leaf maturation and lower optimal temperature for stomatal opening., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A multiplicative stomatal conductance model was constructed to estimate stomatal O3 uptake of Fagus crenata exposed to O3 under different N loads to the soil. Our stomatal conductance model included environmental functions such as the stomatal responses of F. crenata to diurnal changes, chronic O3 stress (AOT0), acute O3 stress (O3 concentration), and nitrogen load to soil. The model could explain 62% of the variability in stomatal conductance. We suggest therefore that stomatal closure induced by O3 and N load-induced soil acidification must be taken into account in developing a stomatal conductance model for estimating stomatal O3 uptake for future risk assessment of O3 impact on Japanese forest tree species such as F. crenata., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

To evaluate the negative impact of ozone (O3) on Japanese crop plant yield based on cumulative stomatal O3 flux, a Japanese rice cultivar, Koshihikari, was exposed to O3 in O3-exposure chambers. Stomatal diffusive conductance to water vapour were measured during the experimental period. We parameterized and improved a stomatal diffusive conductance model by considering seasonal changes in stomatal diffusive conductance, as well as the acute effects of O3 on this variable. Our adjusted model accounted for 64% of the variation within the data set. Based on the results of linear regression analyses of the relationship between relative yield and cumulative O3 uptake, the negative impact of O3 on the yield of Koshihikari can be evaluated using cumulative O3 uptake with a threshold of 10 nmol O3 m(-2) projected leaf area s(-1) and an integration period of -300 to 100 °C days from anthesis., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

To assess the effects of tropospheric O3 on rice cultivated in Bangladesh, four Bangladeshi cultivars (BR11, BR14, BR28 and BR29) of rice (Oryza sativa L.) were exposed daily to charcoal-filtered air or O3 at 60 and 100 nl l(-1) (10:00-17:00) from 1 July to 28 November 2008. The whole-plant dry mass and grain yield per plant of the four cultivars were significantly reduced by the exposure to O3. The exposure to O3 significantly reduced net photosynthetic rate of the 12th and flag leaves of the four cultivars. The sensitivity to O3 of growth, yield and leaf gas exchange rates was not significantly different among the four cultivars. The present study suggests that the sensitivity to O3 of yield of the four Bangladeshi rice cultivars is greater than that of American rice cultivars and is similar to that of Japanese rice cultivars and that O3 may detrimentally affect rice production in Bangladesh., (Copyright (c) 2010 Elsevier Ltd. All rights reserved.)

To clarify the effects of O(3) on crop plants cultivated in Bangladesh, two Bangladeshi wheat cultivars (Sufi and Bijoy) were grown in plastic boxes filled with Andisol and exposed daily to charcoal-filtered air or O(3) at 60 and 100 nl l(-1) (10:00-17:00) from 13 March to 4 June 2008. The whole-plant dry mass and grain yield per plant of the two cultivars at the final harvest were significantly reduced by the exposure to O(3). Although there was no significant effect of O(3) on stomatal diffusive conductance to H(2)O of flag leaf, net photosynthetic rate of the leaf was significantly reduced by the exposure to O(3.) The sensitivity of growth, yield, yield components and leaf gas exchange rates to O(3) was not significantly different between the two cultivars. The results obtained in the present study suggest that ambient levels of O(3) may detrimentally affect wheat production in Bangladesh., (Copyright 2009 Elsevier Ltd. All rights reserved.)

The seedlings of Pinus armandi Franch. were exposed to ozone (O(3)) at 300 ppb for 8 h a day, 6 days a week, and simulated acid rain of pH 3.0 or 2.3, 6 times a week, alone or in combination, for 14 weeks from 15 June to 20 September 1993. The control seedlings were exposed to charcoal-filtered air and simulated rain of pH 6.8 during the same period. Significant interactive effects of O(3) and simulated acid rain on whole plant net photosynthetic rate were observed, but not on other determined parameters. The exposure of the seedlings to O(3) caused the reductions in the dry weight growth, root dry weight relative to the whole plant dry weight, net photosynthetic rate, transpiration rate in light, water-use efficiency and root respiration activity, and increases in shoot/root ratio, and leaf dry weight relative to the whole plant dry weight without an appearance of acute visible foliar injury, but did not affect the dark respiration rate and transpiration rate in the darkness. The decreased net photosynthetic rate was considered to be the major cause for the growth reduction of the seedlings exposed to O(3). On the other hand, the exposure of the seedlings to simulated acid rain reduced the net photosynthetic rate per unit chlorophyll a + b content, but did not induce the significant change in other determined parameters.