Effects of Elevated O<Subscript>3</Subscript> and/or Elevated CO<Subscript>2</Subscript> on Lipid Peroxidation and Antioxidant Systems in <Emphasis Type="Italic">Ginkgo biloba</Emphasis> Leaves

Four-year-old seedlings of Ginkgo biloba were exposed to elevated O₃, elevated CO₂ and elevated O₃ plus elevated CO₂ in open-top chambers (OTCs) to study the responses of antioxidant system in Ginkgo biloba leaves. No significant changes in reactive oxygen production and scavenging systems were detected in seedlings exposed to high CO₂. Significant increase in H₂O₂ and MDA content were induced by elevated O₃. The ascorbate content and antioxidative enzymes activity were increased significantly by exposure to high O₃ as well. But the promoted ability in scavenging did not prevent the increase in H₂O₂ content and cell membrane lipid peroxidation. The increase was mitigated by high CO₂ in the combined exposure, but the effect was hardly significant.     

The Influence of Air Pollution on the Concentration of Airborne Elements and on the Production of Stress-Ethylene in the Lichen Usnea hirta (L.) Weber em. Mot. Transplanted in Urban Sites in Oulu, N. Finland

The purpose of the present study was to examine the response, as indicated by the production of stress-ethylene, of the lichen Usnea hirta, to a buffered acidic solution and to a solution containing bisulfite ion, both at pH 4.0. In addition, the study investigated the accumulation capacity of U. hirta transplanted either to the vicinity of two streets with slow traffic, or to the vicinity of a highway in the city of Oulu, N. Finland for a short period (45 d), and to analyze the comparative production of stress-ethylene and the amounts of airborne elements accumulated in the thallus. Thalli of U. hirta manifested a high accumulation capacity for K, Ca, Na, Mg, Fe, Zn, and Mn in samples exposed in one of the two streets with slow traffic in Oulu, in comparison with thalli left at the control site in the forest outside of the city. Two of the observed elements, Pb and Ca, exhibited a positive correlation with the concentration of ethylene detected consecutive to the treatment of lichen thalli with H₂O (pH 6.8). The concentrations of stress-ethylene in lichen thalli retrieved from the streets with slow traffic and less cars (14,000 per day), soaked in solutions of NaHSO₃ (pH 4.0), were higher than those produced by thalli retrieved from a site near the highway (with 25,000 cars per day) and by thalli left in the forest. It is suggested that the streets with slow traffic and less cars are more polluted than the highway as a result of bad ventilation conditions and a slow rate of dispersion of airborne pollutants. Received: 28 June 1996/Revised: 11 September 1996     

Using estimates of metal bioavailability in the soil and genetic variation of allozymes to investigate heavy metal tolerance in the earthworm Eisenia fetida (Oligochaeta)

In a recent study, we showed that the earthworm species Eisenia fetida, inhabiting an extremely high metal polluted compost heap on a wine farm, did not have elevated body loads of the metals but exhibited genotoxic tolerance when exposed to Cd in the laboratory (Voua Otomo and Reinecke, 2010). To unravel the mechanism behind the surprisingly low metal body burdens on one hand and genotoxic tolerance on the other hand, we investigated the estimated bioavailability of these metals (Cu, Zn, Pb and Cd) using sequential extraction methods with CaCl₂ and di-ethylene-triamine-pentaacetic acid (DTPA) and allozyme polymorphism in this field population, a laboratory control as well as a long-term Cd exposed population. The amounts of mobile (extracted with CaCl₂) and mobilizable (extracted with DTPA) metals in relation to the total (extracted with nitric acid) metals were all below 0.05% for all four metals, suggesting low availability for uptake. The low availability of these metals could not be explained by physico-chemical properties of soil but by the phenomenon of aging of the metals. There was no difference in allozyme frequency between metal tolerant and non-metal tolerant populations of E. fetida. This suggested that the tolerance found in earlier studies could be a mere physiological adaptation     

Effects of Elevated Ozone on Photosynthetic CO<Subscript>2</Subscript> Exchange and Chlorophyll <Emphasis Type="Italic">a</Emphasis> Fluorescence in Leaves of <Emphasis Type="Italic">Quercus mongolica</Emphasis> Grown in Urban Area

The aim of this study was to determine the responses of photosynthesis in leaves of Quercus mongolica to elevated O₃ exposure in an urban area. The results showed that the photosynthesis parameters were all decreased by the elevated O₃ during the whole season. Especially, light-saturated net photosynthetic rate (A) was reduced about 72% after 45 days exposure, and over the whole growing season, the differences were significant (p < 0.05) compared with control. The reduction is related to both stomatal and non-stomatal factors, including a decrease (about 9%) in the maximum quantum yield of PSII photochemistry (F _v/F _m) detected after 90 days O₃ exposure.     

Influence of Elevated Carbon Dioxide and Ozone on the Foliar Nonvolatile Terpenoids in <Emphasis Type="Italic">Ginkgo Biloba</Emphasis>

The aim of this study was to determine the effects of elevated O₃ and elevated CO_2, singly and in combination, on the contents of nonvolatile terpenoids in leaves of Ginkgo Biloba. The results showed that elevated CO₂, alone and in combination with elevated O₃ increased concentrations of all the determined terpenoids, while elevated O₃ alone only increased concentration of bilobalide. These results demonstrated that the metabolism of terpenoids in ginkgo leaves was more sensitive to elevated CO₂ than elevated O₃.     

The impact of air pollution on the integrity of cell membranes and chlorophyll in the lichenRamalina duriaei (de not.) bagl. transplanted to industrial sites in Israel

The impact of air pollution on the integrity of cell membranes and chlorophyll in the lichenRamalina duriaei was studied. The lichen was transplanted from a relatively unpolluted site in Israel to a highly polluted area for a period of 10 months. The seasonal variation of the percentages of Mg as detected with the aid of scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDX) on/in the cortical cells of the lichen was compared with changes in the chlorophyll integrity as expressed by the ratio OD 435 nm/OD 415 nm. The rate of damage of air pollution to cell membranes in the lichen was compared with the increase of S as detected on the surface of the lichen thalli retrieved from industrial sites. The present study indicates that the electric conductivity parameter reflecting the integrity of lichen cell membranes was found to express the cellular damage caused to lichen thalli transplanted to a steel smelter and to oil refineries. Symptoms of damage to cell membranes are detectable inR. duriaei long before any indication of damage becomes apparent in the photobiont chlorophyll. Magnesium seems to represent a significant leakage from intracellular sites of the thallus. The accumulation of sulfur on/in the cortical cells ofR. duriaei indicates that the biomonitoring sites at the Haifa Bay are contaminated by SO₂.     

Physiological and chemical response of lichens transplanted in and around an industrial area of south Italy: relationship with the lichen diversity

The lichen Evernia prunastri (L.) Ach. has been exposed for 3 months in and around an industrial area of Mediterranean Italy for monitoring physiological (photosynthetic efficiency, membrane lipids peroxidation and cell membrane integrity) and chemical (bioaccumulation of the heavy metals Cr, Ni, Pb, V and Zn) effects and investigate the consistency with the environmental quality status depicted by the diversity of epiphytic lichens (index of lichen diversity (ILD)).The results showed that thalli transplanted close to the industrial area exhibited early stress symptoms, as revealed by the increase in electrical conductivity indicating a damage endured by lichen cell membranes. The electrical conductivity was inversely correlated with the diversity of epiphytic lichens recorded at the same sites. The ILD negatively correlated also with membrane lipid peroxidation and the rate of accumulation of Pb, V and Zn. Reciprocal correlations found among trace elements pinpointed vehicular traffic and metal processing in the industrial area as main sources. The damage endured by cell membranes was the best physiological indicator consistent with the air quality status depicted by the diversity of epiphytic lichens.     

Integrity of Lichen Cell Membranes in Relation to Concentration of Airborne Elements

This study dealt with the impact of air pollution on the integrity of cell membranes in the lichen Ramalina duriaei. The lichen was transplanted from a relatively unpolluted site in Israel to more polluted sites, adjacent to a 40-year-old town, for a period of 10 months. The concentrations of K, B, Al, Cr, Fe, Si, Ti, Zn, P, Ba, Cu, Mg, Na, Pb, Ca, Mn, Sr, and S in lichen thalli were compared with injury caused to the cell membranes. The study indicates that electric conductivity reflects adequately cellular injury to lichen thalli transplanted to sites near a motorway, an oil-fueled power plant and a rural community (a kibbutz). The concentrations of S, B, Al, Cr, Fe, Si, Ti, and Zn correlated with injury in cell membranes of R. duriaei retrieved from the biomonitoring sites, whereas the concentration of K in the thalli correlated inversely with the electric conductivity parameter. Leakage of K from lichen thalli as a result of air pollutants is suggested. This K leakage correlates positively with concentrations of S and Cr in transplants of R. duriaei to the Ashdod region. Received: 14 May 1996/Accepted: 26 March 1997     

The role of urban air pollutants on the performance of heavy metal accumulation in Usnea amblyoclada

Lichens incorporate heavy metals according to a selectivity sequence; therefore, their uptake rate can be affected when elements with a high affinity for cell wall exchange sites or that provoke harmful alterations to the metabolism of lichen thalli are present in the environment. The aim of this study was to examine the effect of urban pollutants on the accumulation of some heavy metals in Usnea amblyoclada. Lichen samples were transplanted for 1 month to both a polluted and a nonpolluted area in Cordoba, Argentina. They were then collected and soaked in tridistilled water or in solutions containing different concentrations of Cu, Ni, Pb, and Zn salts. The uptake of Cu2+, Ni2+, Zn2+, and Pb2+, and other parameters indicative of lichen damage were measured in all the lichen samples. The thalli retrieved from the polluted area showed significant increases in both the malonaldehyde content and the electrical conductivity of the water in which they had been immersed. These results indicate that the atmospheric pollutants could be responsible for the significant damage to the lichen's cellular membranes, thus altering several mechanisms related to the uptake of heavy metals. Both the area of transplantation and the concentration of the metallic solutions had significant effects on the levels of Cu, Ni, and Pb measured in lichen thalli; however, no significant differences were observed in Zn concentrations. The highest uptakes corresponded to Pb and Cu, suggesting that they probably have a higher affinity with the lichen cell wall exchange sites. This study confirms the fact that, although lichens can be useful biological indicators, the physiological mechanisms involved in metal uptake should be carefully analyzed. Therefore, when estimating the heavy metal content of an environment, the competitive mechanism for cation uptake should be considered especially in areas where the presence of high levels of metals with a strong binding affinity is suspected. The presence of secondary products in the lichens could be responsible for the selective uptake of cations and for a possible tolerance to their presence.     

Elemental composition and source characterization of airborne PM10 at residences with relative proximities to metal-industrial complex

Objectives: Exposure estimates based solely on proximity to air pollution sources are not robust and require confirmation. Consequently, the present study was designed to scientifically evaluate the atmospheric particulate pollution in residences relative to their proximity to a Korean major metal-industrial complex (MIC). Methods: This purpose was achieved by concurrently measuring the concentrations and elemental composition of particulate matter with aerodynamic diameters equal to or less than 10 μm (PM₁₀) and characterizing the PM₁₀ source types in industrial ambient air from MIC and residential ambient air with relative proximities to MIC. Trace metals were analyzed using an inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The elemental composition data were employed to calculate enrichment factors and statistically analyzed using a principal component analysis (PCA) to characterize the PM₁₀ source types. The source contributions were quantitatively analyzed using an absolute PCA (APCA). Results: The most enriched elements for which a significant anthropogenic origin can be suggested were Cd, Cu, Pb, Sb, Tl, and Zn. For PCA, four or five factors with eigenvalues greater than unity were obtained for each sampling site, and those having high loadings with the same variables represented similar source types. The APCA result yielded significant regression coefficients, explaining 74–85% of the variability in the PM₁₀, which depends on the sampling site. The industrial mean values exceeded the Korean year/70 μg/m³ standard for PM₁₀, whereas the residential mean values did not. However, the maximum residential values did exceed or were close to the Korean PM₁₀ year standard. For individual elements, the ambient concentrations ranged widely from values in the order of a few ng/m³ to thousands of ng/m³. The residential mean mass concentrations in the PM₁₀ measured in the present study were higher than or similar to those reported in earlier studies. Conclusions: The present study confirmed that residents in neighborhoods near the MIC are exposed to elevated particulate and metal levels compared to residents living further away from such a source, thereby supporting that proximity to air pollution sources can be employed to indicate environmental exposure.     

The role of lichens in the cycling of metals in the Negev Desert

The epilithic fruticose lichen Ramalina maciformis (Del.) Bory which grows in the Central Negev Highlands of Israel is grazed by the black dwarf goat of the Bedouins. In order to study the role of R. maciformis in the cycling of metals in the Negev Desert, epilithic thalli growing on flintstones on western aspects of a hill were detached, put in fiberglass window-screen litterbags, and secured on the soil surface of western, southern, and northern aspects of the hill. Simultaneously, flintstones carrying lichen thalli were transferred from west-facing slopes of the hill to adjacent south-facing slopes, where epilithic thalli of R. maciformis were observed to grow in very small quantities. The concentration of the heavy metals were determined in the original lichen material at the beginning of the experiment, and in in situ and relocated thalli after a period of 14 months. The concentrations of Fe, Zn, Mn, Cu, and Pb in the upper soil layer on the different aspects were determined at the end of the experimental period. A comparison of the concentration of heavy metals in epilithic thalli of R. maciformis examined in the same study site a decade ago, and of present findings, reveals a regional increase of airborne Mn and Zn derived from local traffic. The concentration of heavy metals in thalli detached from stones and kept in litterbags was higher than in epilithic thalli. Thalli detached from stones and exposed on northern aspects of the hill contained less heavy metals than those kept on south-facing slopes. It is suggested that detached thalli derive heavy metals from the upper soil layer in addition to elements derived from airborne dust. The decreased concentration of Fe and Mn in epilithic thalli in the experiment period is explained by the enhanced number of washing and freezing actions in the two unusually cold and wet winters of 1990/1991 and 1991/1992. It is suggested that extreme climatic fluctuations regulate the accumulation of minerals in in situ epilithic thalli of desert lichens.     

Respiratory health of bus drivers in Hong Kong

Objective: We conducted a cross-sectional study to evaluate the lung function and respiratory symptoms of Hong Kong bus and tram drivers exposed to air pollutants. Methods: Demographic information, vital signs, pulmonary function, respiratory symptoms and blood lead levels in 358 male drivers of air-conditioned buses (ACB) were compared with 129 male drivers of non-air-conditioned buses and trams (NACB). Particulate matter (PM₁₀), carbon dioxide (CO₂) and carbon monoxide (CO) levels were measured in 16 air-conditioned and 15 non-air-conditioned trams along the same route. Results: Forced vital capacity, forced expiratory volume in 1 s and maximal voluntary ventilation were lower but blood lead levels were higher in the NACB drivers compared with ACB drivers. More NACB drivers compared to ACB drivers reported frequent productive cough, dry cough, as well as sore throat. The measured lung function parameters in the NACB drivers were lower than a cohort of personnel working in an academic environment. The work-year duration was longer and scheduled days off per month were shorter for NACB (13.4±8.8 years and 4.3±1.3 days) compared to ACB drivers (11.5±9 years and 5.4±0.8 days), respectively (P<0.001). The PM₁₀ and CO₂ levels were higher in ACB (265±83 μg/m³ and 2,114±69.6 ppm) compared to non-air-conditioned trams (161±103 μg/m³ and 500 ppm, respectively) (P<0.005). Conclusion: We hypothesise that prolonged exposure to air pollutants adversely affects lung function in our NACB drivers but air recirculation could result in higher blood lead levels in ACB drivers.     

The influence of location, source, and emission type in estimates of the human health benefits of reducing a ton of air pollution

The benefit per ton ($/ton) of reducing PM_2.5 varies by the location of the emission reduction, the type of source emitting the precursor, and the specific precursor controlled. This paper examines how each of these factors influences the magnitude of the $/ton estimate. We employ a reduced-form air quality model to predict changes in ambient PM_2.5 resulting from an array of emission control scenarios affecting 12 different combinations of sources emitting carbonaceous particles, NO _x , SO _x , NH₃, and volatile organic compounds. We perform this modeling for each of nine urban areas and one nationwide area. Upon modeling the air quality change, we then divide the total monetized health benefits by the PM_2.5 precursor emission reductions to generate $/ton metrics. The resulting $/ton estimates exhibit the greatest variability across certain precursors and sources such as area source SO _x , point source SO _x , and mobile source NH₃. Certain $/ton estimates, including mobile source NO _x , exhibit significant variability across urban areas. Reductions in carbonaceous particles generate the largest $/ton across all locations.     

Nickel Exposure Enhances the Susceptibility of Lichens <Emphasis Type="Italic">Usnea amblyoclada</Emphasis> and <Emphasis Type="Italic">Ramalina celastri</Emphasis> to Urban Atmospheric Pollutants

In the present study, the effect of nickel incorporation on the chemical response of Ramalina celastri (Spreng.) Krog & Swinsc. and Usnea amblyoclada (Müll. Arg.) Zahlbr. exposed to urban atmospheric pollutants was assessed. Lichen thalli were treated with Ni solutions and then transplanted to two areas of the city of Córdoba with different levels of pollution. After exposure, the concentration of chlorophyll a, chlorophyll b, phaeophytin a, hydroperoxy conjugated dienes, malondialdehyde, sulphur content, electric conductivity of the immersion water, and nickel content were measured. Also, a Pollution Index was calculated for each lichen species. The exposure to Ni altered the physiological response to atmospheric pollutants in both lichen species, making them more sensitive to any damage caused by them. When the species were compared, it was observed that R. celastri accumulated more sulphur than U. amblyoclada.     

Evaluation of glyphosate drift and anthropogenic atmospheric trace elements contamination by means of lichen transplants in a southern Italian agricultural district

Ecophysiological biomarkers and atmospheric contamination due to glyphosate and trace elements were monitored in a southern Italian agricultural district by means of transplanted thalli of the lichen Pseudevernia furfuracea. Glyphosate exhibited a significant geographical pattern (east side?>?west side) and a drift source area equal to 32% of the monitoring sites. Moreover, based on the surface area of the study area and a wind quantitative relationship (WQR) with glyphosate thalli concentrations, our data support the idea that pesticide drift extends over an area of several square kilometers. Of the eight elements preliminarily classified as enriched, four were considered prevalently of geogenic origin (Al, Ti, Ni, Co) and four of anthropogenic origin (Cu, Mn, Sn, Sb), although only Sb and Cu passed rigorous statistical testing supporting a real difference from pre-exposure levels. The contribution of local sources was evaluated based on the relative increase of Cu, Mn, Sb, and Sn versus Ti. Cu and Mn were associated mainly with a biomass power plant (BPP), with Cu showing extremely high levels of contamination involving 20% of the monitoring sites. Sb and Sn were associated with spatial variation of the traffic rate. The mycobiont and photobiont showed an evident zonation of the levels of their physiological parameters, with oxidative stress being significantly associated with both the biomass power plant and Cu/Ti. Our results suggest that croplands are potentially exposed to various hazards: over-exposure to pesticides due to drift processes, diffuse low traffic levels promoting Sb enrichment, and acute Cu pollution affected by BPP emissions.     

Impact of Elevated CO<Subscript>2</Subscript> and O<Subscript>3</Subscript> Concentrations on Biogenic Volatile Organic Compounds Emissions from <Emphasis Type="Italic">Ginkgo biloba</Emphasis>

In natural environment with ambient air, ginkgo trees emitted volatile organic compounds 0.18 μg g⁻¹ h⁻¹ in July, and 0.92 μg g⁻¹ h⁻¹ in September. Isoprene and limonene were the most abundant detected compounds. In September, α-pinene accounted for 22.5% of the total. Elevated CO₂ concentration in OTCs increased isoprene emission significantly in July (p < 0.05) and September (p < 0.05), while the total monoterpenes emission was enhanced in July and decreased in September by elevated CO₂. Exposed to elevated O₃ increased the isoprene and monoterpenes emissions in July and September, and the total volatile organic compounds emission rates were 0.48 μg g⁻¹ h⁻¹ (in July) and 2.24 μg g⁻¹ h⁻¹ (in September), respectively. The combination of elevated CO₂ and O₃ did not have any effect on biogenic volatile organic compounds emissions, except increases of isoprene and Δ3-carene in September. Foundation item: The National Natural Science Foundation of China (No. 90411019).     

Prostaglandin E2 production in mice is reduced by consumption of range-fed sources of red meat

Many view bison as a healthful alternative to other red meat sources, and as a way to decrease health risks, they associate it with meat consumption. Using mice as a model for immune function, we hypothesized that consumption of meat from range-fed bison would decrease prostaglandin (PG) E₂ and alter prostacyclin (PGI₂) release upon immune challenge when compared with mice fed meat from grain-finished bison, range-fed beef, feedlot steers, free-ranging elk, or chicken breast. After 2 weeks on an experimental diet and inflammatory stimulation, mouse peritoneal macrophage was isolated and analyzed in 12 animals per diet. Peritoneal cell arachidonic acid increased in response to a chicken-based diet (P < .05), which was likely attributable to higher arachidonic acid intake. Release of PGE₂ was lowest in mice consuming meat of range-fed beef, range-fed bison, and elk but was highest with meat of grain-finished beef and intermediate in mice fed chicken (P < .05). Mice fed elk meat had the greatest PGI₂, whereas PGI₂ was decreased in mice fed meat of either range bison, range beef, or chicken (P < .05) and intermediate in mice fed meat of steers or bison finished in a feedlot. We conclude that consumption of meats characteristic of range-fed ruminants or wild ungulates supports reduced PGE₂ and greater PGI₂ synthesis, indicating potentially greater immune health and lower blood clotting potential than meat from grain-finished cattle or bison in this model system.     

Investigation of CO2 production depending on physical activity of students

This paper aims to carry out measurements of indoor air temperature, relative humidity and carbon dioxide (CO₂) concentrations as well as to determine CO₂ production by students and teacher during various physical activities. Two classrooms of Technical University of Kosice were selected for the research. Results of objective measurements confirmed strong correlation between CO₂ concentration occupancy for all measurements. Recommended value for indoor CO₂ level according to Pettenkofer (1,000 ppm) was exceeding in 60.9%. Results of this study showed the insufficient ventilation intensity in classrooms as well as obvious rise of CO₂ concentration during the exams. The highest increase of CO₂ was recorded during harder physical activity (run on the spot, squats, right and left side lunges, and rotating of the hips). Regarding CO₂ production by respondents it can be see that it is visibly increased with increasing physical activity.     

Comparison of germination, growth, photosynthetic responses and metal uptake between three populations of Spartina densiflora under different soil pollution conditions

Spartina densiflora has demonstrated a high tolerance to heavy metal contamination and a high capacity for accumulating metal in its tissues. In the Gulf of Cadiz this species has colonized habitats with different degrees of metal pollution. The aim of this study is to analyse the responses of populations of Spartina densiflora to this pollution. Germination, growth, photosynthesis and metal uptake of two populations of Spartina densiflora collected from contaminated sites (Odiel and Tinto marshes) and of one population from a clean site (Piedras marshes) were examined through two reciprocal experiments, in which seeds and adult plants were exposed to metal-contaminated and uncontaminated soil under greenhouse conditions. The seeds of Spartina densiflora were able to germinate in all sediments with little differences between populations, even in more contaminated soils. However, these conditions decreased the growth and survival of the seedlings to a similar degree for all populations. Likewise, no differences were recorded in relation to physiological and metal uptake. Contrarily, in the adult experiment, we found that the Odiel population differed from the other populations in growth and metal uptake, with overall greater values. These differences in growth were strongly supported by lower photosynthetic rates and stomatal conductance in the Piedras and Tinto populations. The reduction in photosynthetic performance was largely due to the reduction in photosynthetic pigment concentration in both populations. Despite these differences, there was insufficient evidence to support that Spartina has evolved to heavy-tolerant ecotypes, since all Spartina densiflora populations proved to have a great capacity for accumulating heavy metals in its roots. Nonetheless, this finding suggests that the Odiel population could have a greater phytoremediation potential.     

Effects of Elevated CO<Subscript>2</Subscript> and O<Subscript>3</Subscript> on Phenolic Compounds in Spring Wheat and Maize Leaves

C₃ crops are generally considered more sensitive than C₄ crops to the elevated CO₂ and O₃, but it is unclear whether the concentrations of phenolic compounds in them are affected. In this paper, an enrichment experiment with open-top chamber was conducted to examine the effects of elevated CO₂, O₃, and their combination on the contents of total phenolic compounds and flavone in the leaves of spring wheat (C₃ crop) and maize (C₄ crop). The results showed for spring wheat, the total phenolic contents in its leaves at jointing stage was significantly higher under elevated CO₂ and/or O₃, with the sequence of CO₂ plus O₃ > O₃ > CO₂ > ambient, while at grain-filling stage, the total phenolic content was lower under CO₂ plus O₃ than under CO₂, O₃, and ambient. The total phenolic content in maize leaves at jointing stage had the similar variation trend with that for wheat, but at grain-filling stage, the total phenolic content was slightly affected by elevated CO₂ and/or O₃. The flavone content in spring wheat leaves was significantly lower under CO₂ and/or O₃ stress at jointing stage, but had lesser difference at grain-filling stage under the stress. The same variation trend was observed in the flavone content in maize leaves at jointing and grainfilling stages, i.e., CO₂ plus O₃ > CO₂ > ambient > O₃. C₃ plant was more sensitive than C₄ plant to the CO₂ and/or O₃ stress. Foundation item: The National Natural Science Foundation of China (No. 30570348 and 30500069).