Free-air Ozone Enrichment Research Articles

Interactive effect of ambient and elevated levels of tropospheric ozone, nutrition and PGPR on growth and yield of chickpea (Cicer arietinum)

An experiment was conducted during 2020 and 2021 at ICAR-Indian Agricultural Research Institute, New Delhi, to study the interactive effect of nutrient and PGPR (Plant growth promoting rhizobacteria) on growth and yield of chickpea (Cicer aeritinum L.) cv. Pusa 3043 under ambient and elevated levels of ozone in FAOE (Free air ozone enrichment). A loss of 15–16% in dry matter production was observed under elevated ozone (EO3) when compared to ambient ozone (AO3) conditions. Seed treatment with PGPR was found to compensate for this loss as an increase in seed yield 18–19% was observed over untreated seeds. In terms of seed yield, the PGPR treatments with 75% nitrogen showed significant improvement compared to the recommended dose of fertilizer (RDF) application. A yield increase of 12% and 14% was observed with PGPR like RPAN8 (Anabena laxa) and An-Rh (Anabena torulosa with Mesorhizobium ciceri) (chickpea rhizobium) respectively, suggesting an advantage of an–Rh over RPAN8 under EO3. A combination of both PGPRs outperformed the individual PGPR, showing a 19% yield increase over RDF. This proves the potential of seed treatment with PGPR (RPAN8 and An-Rh) in ameliorating tropospheric ozone-induced stress in chickpea plants.

Response of tropical trees to elevated Ozone: a Free Air Ozone Enrichmentstudy.

Tropospheric ozone (O3) has become one of the main urban air pollutants. In the present study, we assessed impact of ambient and future ground-level O3 on nine commonly growing urban tree species under Free Air Ozone Enrichment (FAOE)condition. During the study period, meanambient and elevated ozone (EO3) concentrations were 48.59 and 69.62ppb, respectively. Under EO3 treatment,stomatal density (SD) significantly decreased and guard cell length (GCL) increased in Azadirachta indica, Bougainvillea spectabilis, Plumeria rubra, Saraca asoca and Tabernaemontana divaricata, while SD increased and GCL decreased in Ficus benghalensis and Terminalia arjuna. Proline levels increased in all the nine plant species under EO3 condition. EO3 significantly reduced photosynthetic rate, stomatal conductance (gs), and transpiration rates (E). Only A. indica and N. indicum showed higher gs and E under EO3 treatment. Water use efficiency (WUE) significantlyincreased in F. benghalensis anddecreased in A. indica and T. divaricata. Air Pollution Tolerance Index (APTI) significantly increased in Ficus religiosa and S. asoca whereas it decreased in B. spectabilis and A. indica. Of all the plant species B. spectabilis and A. indica were the mostsensitive to EO3 (high gs and less ascorbic acid content) whileS. asoca and F. religiosa were the mosttolerant (lowgs and more ascorbic acid content). The sensitivity of urban tree species to EO3 is a cause ofconcern and should be considered for future urban forestry programmes. Our study should guidemore such studies toidentify tolerant trees for urban air pollution abatement.

Cultivar assortment index (CAI): a tool to evaluate the ozone tolerance of Indian Amaranth (Amaranthus hypochondriacus L.) cultivars.

The adverse impact of climate change on crop yield has accelerated the need for identification of crop cultivars resistant to abiotic stress. In the present study, a cultivar assortment index (CAI) was generated for the evaluation of forty Amaranthus hypochondriacus cultivars response to elevated ozone (EO) concentrations (AO + 30ppb) in Free Air Ozone Enrichment (FAOE) facility using the parameters viz. foliar injury, gaseous exchange attributes, namely, net photosynthetic rate, stomatal conductance, transpiration rate, intercellular carbon dioxide, and water use efficiency along with above ground biomass and grain yield attributes. The dataset was used to identify key indicator parameters responsive to EO through principal component analysis (PCA) and further transformed to obtain linear score and weighted score. The CAI varied from 70.49 to 193.43. Cultivars having CAI value less than 151 were ozone tolerant (OT) whereas cultivars with CAI values between 150 and 170 were moderately tolerant (MOT). The cultivars exhibiting CAI values above 170 were ozone sensitive (OS). The cultivars exhibited differential sensitivity to EO with IC-5994 (CAI = 187.26) being the most affected cultivar whereas IC-5576 (CAI = 83.38) and IC-5916 (CAI = 70.49) being the least affected ones. The CAI, based on linear score and weighted score, offers easy identification of ozone sensitive (OS) and ozone tolerant (OT) cultivars. This index could help researchers to define a clear and strong basis for identification of OT cultivars which will reduce the time required for preliminary screening and further evaluation of crop cultivars for the development of climate smart crops.

Effects of tropospheric ozone and elevated nitrogen input on the temperate grassland forbs Leontodon hispidus and Succisa pratensis

Atmospheric ozone (O3) and nitrogen (N) pollution have increased since pre-industrial times and pose a threat to natural vegetation. The implications of these pollutants for the perennial temperate grassland species Leontodon hispidus (Rough Hawkbit) and Succisa pratensis (Devil’s-bit Scabious) are largely unknown. Both species are important for pollinators and Succisa pratensis is the host plant for the threatened marsh fritillary butterfly (Euphydryas aurinia).We examine growth and physiological responses (leaf cover, leaf litter, flowering, chlorophyll index [Leontodon hispidus and Succisa pratensis]; photosynthesis and stomatal conductance [Succisa pratensis]) using an outdoor Free Air Ozone Enrichment system. Plants were exposed to Low, Medium and High ozone treatments over three growing seasons (treatment means: 24, 40 and 57 ppb, respectively), with and without the addition of nitrogen (40 kg ha−1 yr−1) during the first year.Decreases in leaf cover (p < 0.001) and chlorophyll index (p < 0.01) were observed with increased O3 for Leontodon hispidus. The addition of N resulted in a higher chlorophyll index only at the uppermost O3 level and also led to an overall increase in litter production of 6%. However, a stronger effect of both O3 and N treatments was observed with Succisa pratensis. Litter production increased with increasing O3 (p < 0.001) and an overall rise of 31% was recorded with added N (p < 0.05). However, O3 had the biggest impact on Succisa pratensis foliage leading to more damaged leaves (p < 0.05). During summer resources were prioritised to new leaves, maintaining stomatal conductance and photosynthesis rates. However, this was not sustained during autumn and accelerated senescence occurred with higher ozone, and rates declined faster with added nitrogen (p < 0.05). Elevated O3 also reduced Succisa pratensis flowering (p < 0.01).These effects have implications for inter- and intra-specific competition, seed establishment, nutrient cycling, as well as the provision of general pollinator resources with specific issues for butterfly larvae. Results highlight the need for concerted action to reduce pre-cursor ozone emissions to go alongside habitat management efforts to protect biodiversity.

Ozone tolerant maize hybrids maintain Rubisco content and activity during long-term exposure in the field.

Ozone pollution is a damaging air pollutant that reduces maize yields equivalently to nutrient deficiency, heat, and aridity stress. Therefore, understanding the physiological and biochemical responses of maize to ozone pollution and identifying traits predictive of ozone tolerance is important. In this study, we examined the physiological, biochemical and yield responses of six maize hybrids to elevated ozone in the field using Free Air Ozone Enrichment. Elevated ozone stress reduced photosynthetic capacity, in vivo and in vitro, decreasing Rubisco content, but not activation state. Contrary to our hypotheses, variation in maize hybrid responses to ozone was not associated with stomatal limitation or antioxidant pools in maize. Rather, tolerance to ozone stress in the hybrid B73 × Mo17 was correlated with maintenance of leaf N content. Sensitive lines showed greater ozone‐induced senescence and loss of photosynthetic capacity compared to the tolerant line.

Screening of forty Indian Amaranthus hypochondriacus cultivars for tolerance and susceptibility to tropospheric ozone stress

Tropospheric ozone stress adversely affects crop cultivars growth and productivity variably. The variable response of crop cultivars raised the need for identification of ozone (O3) stress-tolerant cultivars as an adaptive option. In the present study, forty cultivars of Amaranthus hypochondriacus were screened for susceptibility and tolerance to ozone stress. The cultivars were exposed to ambient (AO3) and elevated (EO3) ozone levels in free air ozone enrichment (FAOE) facility and monitored for foliar ozone injury symptoms appearance and yield attributes response. Foliar ozone injury symptoms on Amaranthus cultivars were interveinal yellow or black spots. Foliar ozone injury was observed in almost half of the cultivars and the maximum foliar injury (> 75%) was observed in cultivar IC-5527. The maximum yield reduction (> 90%) was observed in cultivars IC-4200 (94.9%) and IC-5569 (91.4%) compared to other cultivars. The results showed that Amaranthus cultivars exhibited variable response towards ozone stress where foliar ozone injury does not always correspond with grain yield reductions. Among the indices, Relative Yield Index (RYI), Stress tolerance (TOL), Abiotic Tolerance Index (ATI), Susceptibility Index (S) and Stress Susceptibility Index (SSSI) were positively correlated with relative yield loss in all the cultivars under ozone stress. With the help of cluster analysis and principal component analysis (PCA), the cultivars were categorized into ozone tolerant, moderately ozone tolerant and ozone susceptible category. The most tolerant cultivars were IC-5527 and IC-1733 which exhibited lower yield losses whereas the most susceptible cultivars were IC-3599 and IC-7924 having high foliar injury and maximum yield losses as compared to other cultivars. The most ozone tolerant cultivars of Amaranthus identified in this study may be recommended for cultivation to farmers in the areas experiencing EO3 during the Amaranthus crop growth period.

Litter decomposition and soil mesofauna in a free-air ozone enrichment system

Litter decomposition and soil mesofauna in a free-air ozone enrichment system

Impact of Elevated Ozone on Nutrient Uptake and Utilization of Chinese Hybrid Indica Rice (Oryza Sativa) Cultivars under Free-Air Ozone Enrichment

ABSTRACTTo assess the effects of ozone (O3) on uptake and utilization of nitrogen, phosphorus, and potassium nutrients in rice for planning rational fertilization under projected O3 elevation. Two hybrid indica cultivars were exposed to ambient and elevated O3 (E-O3) under a free-air O3 enrichment system. E-O3 differently affected the accumulation and distribution of biomass, and the absorption and distribution of nutrients between cultivars. These effects were related to rice cultivar and nutrient type. E-O3 led to significantly decreased partial factor productivity and grain production efficiency (GPE) of nitrogen in both cultivars; however, the effects of E-O3 on GPEs of phosphorus and potassium varied with cultivar. Responses of nutrients harvest indices between cultivars to E-O3 were adverse. Differences between cultivars and elements should be considered when examining E-O3 potentially affecting the nutrient dynamics for the purpose of reducing the amount of fertilizer applied in paddy systems to decrease potential environmental pollution.

Cultivar specific plant-soil feedback overrules soil legacy effects of elevated ozone in a rice-wheat rotation system

Tropospheric ozone has been recognized as one of the most important air pollutants. Many studies have shown that elevated ozone negatively impacts yields of important crops such as wheat or rice, but how ozone influences soil ecosystems of these crops and plant growth in rotation systems is less well understood. Using soil collected from a free-air ozone enrichment experiment running for 5 years, we carried out a plant-soil feedback experiment under greenhouse conditions to evaluate the influence of wheat cultivars (Triticum aestivum L.) with different ozone-tolerance on rice (Oryza sativa L.) grown in soils with or without a history of ozone exposure. Our results indicate that there were interactive effects of wheat cultivar and history of ozone exposure on soil respiration and the abundance of fungivorous nematodes. Moreover, the soil microbial community and the abundance of omnivorours-predatory nematodes varied in different wheat cultivars. These differences in the soil, in turn, had feedback effects on the succeeding growth of rice. Rice grown in soil in which previously the ozone-sensitive wheat cultivars Yangmai 2 or Yangmai 19 had grown, had lower shoot biomass than rice grown in the ozone-tolerant wheat cultivars Yangmai 16 soil. However, these cultivar specific effects on rice growth were independent from the previous ozone exposure of the soil. Our results suggest that, in rice-wheat rotation systems, when selecting wheat cultivars to cope with changing climatic conditions, such as elevated ozone, growers should consider the soil-feedback effects of these cultivars on the succeeding crop.

Legacy effects of elevated ozone on soil biota and plant growth

Many studies have examined how human-induced atmospheric changes will influence ecosystems. The long-term consequences of human induced climate changes on terrestrial ecosystems may be determined to a large extend by how the belowground compartment will respond to these changes. In a free-air ozone enrichment experiment running for 5 years, we reciprocally transplanted soil cores from ambient and elevated ozone rings to test whether exposure to elevated ozone results in persistent changes in the soil biota when the plant and soil are no longer exposed to elevated ozone, and how these legacy effects of elevated ozone influenced plant growth as compared to current effects of elevated ozone. After one growing season, the current ozone treatment enhanced plant growth, but in soil with a historical legacy of elevated ozone the plant biomass in that soil was reduced compared to the cores originated from ambient rings. Current exposure to ozone increased the phospholipid fatty acids of actinomycetes and protozoa, however, it decreased dissolved organic carbon, bacterivorous and fungivorous nematodes. Interestingly, numbers of bacterivorous and fungivorous nematodes were enhanced when soils with a legacy of elevated ozone were placed under elevated ozone conditions. We conclude that exposure to elevated [O3] results in a legacy effect in soil. This legacy effect most likely influenced plant growth and soil characteristics via responses of bacteria and fungi, and nematodes that feed upon these microbes. These soil legacies induced by changes in soil biotic community after long-term exposure of elevated ozone can alter the responses of ecosystems to current climatic changes.

Elevated ozone increases nitrifying and denitrifying enzyme activities in the rhizosphere of wheat after 5 years of fumigation

Backgrounds and aims Nitrogen (N) cycling in agroecosystems is likely to change under elevated O3 (eO3) as a result of changes in plant material inputs to soils. The objective of this study was to understand how eO3 could change key N cycling processes in soils. Methods Rhizosphere soils were collected from sensitive and tolerant wheat cultivars following a 5-year fumigation of O3at 60 ppb (eO3) and at ambient 40 ppb (aO3 )i n a free-air ozone enrichment platform. Soil nitrifying and denitrifying enzymeactivity(NEA andDEA), abundance of ammonia monooxygenase(amoA) and denitrifying bacteriagenes(nirSandnirK), and other related properties were quantified. Results Soil NEA, DEA, NH4 + and NO3 � were higher under eO3 than under aO3, whereas microbial biomass N (MBN) decreased under eO3 ,e specially with the O3sensitive cultivar. No clear eO3 effect was observed on the abundance of amoA and nirS and nirK. Grain yield and shoot to root ratios decreased as a result of eO3 in the O3-sensitive cultivar. Conclusions eO3 stimulates soil N availability, but suppresses grain yields after 5 years, especially for the O3sensitive cultivar. Adaptivestrategiesshould focus more on cultivar selection to retain N in soil and to assure the resilience of crop production in the future.

The interactive effects of elevated ozone and wheat cultivars on soil microbial community composition and metabolic diversity

Human-induced global changes have important impacts on terrestrial ecosystems. Although aboveground influences of elevated ozone have been widely studied, relatively little attention has been paid to the belowground subsystem, nevertheless it is critical to study belowground effects in determining the long-term consequences of ozone exposure to ecosystems. Here, we investigated the effects of elevated ozone on soil microbial community structure and functional diversity using the free-air ozone enrichment platform (FAOE). We detected that soil fungal phospholipid fatty acid and the fungal/bacterial ratio were significantly ower under elevated ozone than under ambient ozone at the wheat ripening stage. Through determining soil microbial metabolic diversity as evaluated by variations in the microbial utilization rates of different carbon sources among different wheat cultivars, we found that soil microbial communities inhabiting the rhizosphere of ozone-tolerant cultivars preferred to consume easily degradable carbon sources, while more complex carbon sources were preferably utilized by those associated with ozone-sensitive cultivars. These changes may in turn promote (ozone-tolerant wheat cultivars)/inhibit (ozone-sensitive wheat cultivars) plant growth through alterations in nutrient availability and resource distribution.

Elevated tropospheric ozone increased grain protein and amino acid content of a hybrid rice without manipulation by planting density

Rising tropospheric ozone affects crop yield and quality. Rice protein concentration, which is closely associated with eating/cooking quality, is of critical importance to nutritional quality. The ozone effect on amino acids of rice grains was little known, especially grown under different cultivation conditions. A hybrid rice cultivar Shanyou 63 was grown in 2010 and 2011 to investigate the interactive effect of ozone exposure and planting density on rice protein quality in a free-air ozone enrichment system. The content of protein, total amino acids (TAA), total essential (TEAA) and non-essential amino acids (TNEAA) in rice grain was increased by 12-14% with elevated ozone. A similar significant response to ozone was observed for concentrations of the seven essential and eight non-essential amino acids. In contrast, elevated ozone caused a small but significant decrease in percentage of TEAA to TAA. The year effect was significant for all measured traits; however, interactions of ozone with year or planting density were not detected. The study suggested that season-long elevation of ozone concentration to projected 2050 levels will increase protein and amino acids of Shanyou 63, and crop management such as changing planting density might not alter the impact.

Estimation of stomatal ozone uptake for Fagus crenata grown under free air ozone enrichment system

Estimation of stomatal ozone uptake for Fagus crenata grown under free air ozone enrichment system

開放系オゾン暴露実験を用いたブナ葉の気孔応答へのオゾンの影響‐光合成・気孔コンダクタンスモデルを用いた解析-

開放系オゾン暴露実験を用いたブナ葉の気孔応答へのオゾンの影響‐光合成・気孔コンダクタンスモデルを用いた解析-

Effects of ozone on stomatal response for Fagus crenata grown under free air ozone enrichment system

Effects of ozone on stomatal response for Fagus crenata grown under free air ozone enrichment system

Soil microbial food web responses to free-air ozone enrichment can depend on the ozone-tolerance of wheat cultivars

Soil processes are driven by soil organisms and their interactions with plants and soil abiotic conditions. Climate changes may directly or indirectly alter soil processes and the organisms mediating these processes. Although aboveground influences of ozone have been studied widely on agroecosystems, the effects on belowground processes are poorly understood. This study aimed to investigate the effects of elevated ozone concentration [O3] on the components of soil microbial food webs and compare their responses between ozone-sensitive and ozone-tolerant wheat cultivars. The responses of soil biota to elevated [O3] varied between the two wheat cultivars. Fungal PLFA and the fungi to bacteria ratio decreased following elevated [O3], especially in the rhizospheric soil of ozone-tolerant wheat. Nematode functional guilds were sensitive to elevated [O3] and cultivar effects. At wheat jointing stage, bacterivores belonging to K-strategies decreased following elevated [O3], while fungivores exhibited a reverse trend. The abundance of flagellates decreased in ozone-tolerant wheat, but increased in ozone-sensitive wheat following elevated [O3]. However, an opposite trend was found in the bacterivores belonging to r-strategies. In conclusion, wheat cultivars play an important role in determining the effects of elevated [O3] on soil food web. The responses of soil biota to elevated [O3] were greater in ozone-tolerant wheat than in ozone-sensitive wheat, which may in turn have influenced soil organic matter decomposition and nutrient turnover.

Interactive effects of elevated ozone and springtime frost on growth and physiology of birch (Betula pendula) in field conditions

We studied the impact of ozone enrichment and late frost, singly and interactively, on four birch (Betula pendula Roth) families selected from a naturally regenerated birch stand in southeastern Finland. Seedlings were exposed to 1.5× ambient ozone over one and a half growing seasons using free-air ozone enrichment system. Simulated springtime frost was implemented at the beginning of the second study year, 4 weeks after the bud burst. Plants were measured for timing of bud burst, visible ozone injuries, chlorophyll fluorescence, net photosynthesis and concentrations of photosynthetic pigments, as well as for growth and carbon allocation. Frost treatment caused a rapid 60% decline in net photosynthesis. The recovery of net photosynthesis from acute frost treatment was not complete during the subsequent 3 weeks, which led to significant growth reductions, decreased shoot/root ratio and accumulation of excess nitrogen in the leaves. Photosynthetic responses to ozone were very variable and family-specific. Concentrations of photosynthetic pigments were sensitive to both stress factors, while the maximum quantum yield of PSII was unaffected. Ozone exacerbated the effect of frost only on diameter increment. However, ozone and frost affected different seedling characters, e.g., ozone reduced pigments and frost collapsed net photosynthesis, and these effect combined appear to damage birch seedlings more than a single stress situation.

Oxygen and carbon isotopic signatures reveal a long-term effect of free-air ozone enrichment on leaf conductance in semi-natural grassland

The effect of ozone on leaf gas diffusion was investigated by analyzing the stable oxygen isotopic signatures (δ 18O) in leaves of Holcus lanatus L., Plantago lanceolata L., Ranunculus friesianus (Jord.), and Trifolium pratense L. grown in temperate, semi-natural grassland. Dried material from plants exposed to ambient or elevated ozone levels in a long-term free-air experiment was sampled in 2002 and 2003. A general increase in δ 18O in elevated ozone indicated increased limitation to gas diffusion, which was strongest during the driest and warmest period in 2003. In three out of four species, the increase in δ 18O paralleled an increase in δ 13C measured earlier in the same samples, meaning that the dominant effect of ozone was on gas diffusion and not on CO 2 fixation. Only in R. friesianus, ozone affected both processes simultaneously. It is concluded that elevated ozone not only affects productivity, but also the water status of important component species of grassland communities.