Ozone affects plant, insect, and soil microbial communities: A threat to terrestrial ecosystems and biodiversity

Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced. The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100

Ozone affects plant, insect, and soil microbial communities: a threat to terrestrial ecosystems and biodiversity

Elevated tropospheric ozone concentrations induce adverse effects in plants. We reviewed how ozone affects (i) the composition and diversity of plant communities by affecting key physiological traits; (ii) foliar chemistry and the emission of volatiles, thereby affecting plant-plant competition, plant-insect interactions, and the composition of insect communities; and (iii) plant-soil-microbe interactions and the composition of soil communities by disrupting plant litterfall and altering root exudation, soil enzymatic activities, decomposition, and nutrient cycling. The community composition of soil microbes is consequently changed, and alpha diversity is often reduced. The effects depend on the environment and vary across space and time. We suggest that Atlantic islands in the Northern Hemisphere, the Mediterranean Basin, equatorial Africa, Ethiopia, the Indian coastline, the Himalayan region, southern Asia, and Japan have high endemic richness at high ozone risk by 2100

Strategic roadmap to assess forest vulnerability under air pollution and climate change

Although it is an integral part of global change, most of the research addressing the effects of climate change on forests have overlooked the role of environmental pollution. Similarly, most studies investigating the effects of air pollutants on forests have generally neglected the impacts of climate change. We review the current knowledge on combined air pollution and climate change effects on global forest ecosystems and identify several key research priorities as a roadmap for the future. Specifically, we recommend (1) the establishment of much denser array of monitoring sites, particularly in the South Hemisphere; (2) further integration of ground and satellite monitoring; (3) generation of flux-based standards and critical levels taking into account the sensitivity of dominant forest tree species; (4) long-term monitoring of N, S, P cycles and base cations deposition together at global scale; (5) intensification of experimental studies, addressing the combined effects of different abiotic factors on forests by assuring a better representation of taxonomic and functional diversity across the similar to 73,000 tree species on Earth; (6) more experimental focus on phenomics and genomics; (7) improved knowledge on key processes regulating the dynamics of radionuclides in forest systems; and (8) development of models integrating air pollution and climate change data from long-term monitoring programs.</p

Wild plant species as subjects in O₃ research

Tropospheric ozone (O3) occurs in high concentrations nowadays and affects a many plant species in Northern hemisphere. Numerous wild plant species are known to be negatively affected by O3, and this may impact biodiversity and ecosystems in near future. Given the importance of O3 research with wild plants, we provide a list of 473 relevant taxa - that have been used as a subject of O3 research - as a research material, under various controlled-environment facilities, along with information about their response to O3. In addition, we include species which have been reported that they had developed ozone-like (but not confirmed) symptoms. This list of taxa along with the references is considered an important database, useful to researchers when planning their relevant investigations

Model-based estimation of the leaf area of ozone-indicator tobacco (Nicotiana tabacum L.) plants under ambient ozone conditions

Bel-W3 is an ozone-sensitive tobacco (Nicotiana tabacum L.) cultivar widely used worldwide for ozone biomonitoring. Despite its extensive use, there is no comprehensive predictive model to non-destructively estimate the leaf area using only a common ruler, yet leaf area is a major evaluative trait in plants under ozone stress and of economic value in tobacco plants. In this method, we aimed at developing a predictive model to estimate leaf area using the product between leaf length and leaf width. To this end, we conducted a field experiment with ground-grown Bel-W3 plants treated with different solutions under ambient ozone conditions. The solutions were water, the antiozonant ethylenediurea (EDU; 500 ppm), and the antitranspirant pinolene (Vapor Gard; 1%, 5%, 10%). The chemical treatments were introduced to enhance leaves pool and capture different conditions that can occur in ozone biomonitoring projects. • A simple linear predictive model was developed and validated using data from a previous chamber experiment with small seedlings. • Overestimation of the model led to the integration of data from both experiments and development of another simple linear predictive model. • This integrated model provides improved estimation of leaf area and can be used for representative estimation of the area of Bel-W3 leaves of any sizes

High doses of ethylenediurea (EDU) as soil drenches did not increase leaf N content or cause phytotoxicity in willow grown in fertile soil

Ground-level ozone (O₃) levels are nowadays elevated in wide regions of the Earth, causing significant effects on plants that finally lead to suppressed productivity and yield losses. Ethylenediurea (EDU) is a chemical compound which is widely used in research projects as phytoprotectant against O₃ injury. The EDU mode of action remains still unclear, while there are indications that EDU may contribute to plants with nitrogen (N) when the soil is poor in N and the plants have relatively small leaf area. To reveal whether the N content of EDU acts as a fertilizer to plants when the soil is not poor in N and the plants have relatively large total plant leaf area, willow plants (Salix sachalinensis Fr. Schm) were exposed to low ambient O₃ levels and treated ten times (9-day interval) with 200 mL soil drench containing 0, 800 or 1600 mg EDU L⁻¹. Fertilizer was added to a nutrient-poor soil, and the plants had an average plant leaf area of 9.1 m² at the beginning of EDU treatments. Indications for EDU-induced hormesis in maximum electron transport rate (Jmax) and ratio of intercellular to ambient CO₂ concentration (Ci:Cₐ) were observed at the end of the experiment. No other EDU-induced effects on leaf greenness and N content, maximum quantum yield of photosystem II (Fv/Fm), gas exchange, growth and matter production suggest that EDU did not act as N fertilizer and did not cause toxicity under these experimental conditions

Impacts of ethylenediurea (EDU) soil drench and foliar spray in Salix sachalinensis protection against O3-induced injury

It is widely accepted that elevated levels of surface ozone(O-3) negatively affect plants. Ethylenediurea (EDU) is a synthetic substance which effectively protects plants against O-3-caused phytotoxicity. Among other questions, the one still open is: which EDU application method is more appropriate for treating fast-growing tree species. The main aims of this study were: (i) to test if chronic exposure of Salix sachalinensis plants to 200-400 mg EDU L-1, the usually applied range for protection against O-3 phytotoxicity, is beneficial to plants; (ii) to evaluate the effects of chronic exposure to elevated O-3 on S. sachalinensis; (iii) to assess the efficacy of two methods (i.e. soil drench and foliar spray) of EDU application to plants; (iv) to investigate the appropriate concentration of EDU to protect against elevated O-3-induced damage in S. sachalinensis; and (v) to compare the two methods of EDU application in terms of effectiveness and EDU consumption. Current-year cuttings grown in infertile soil free from organic matter were exposed either to low ambient O-3 (AOZ, 10-h approximate to 283 nmol mol(-1)) or to elevated O-3 (EOZ, 10-h approximate to 65.8 nmol mol(-1)) levels during daylight hours. Over the growing season, plants were treated every nine days with 200 mL soil drench of 0, 200 or 400 mg.EDU L-1 or with foliar spray of 0, 200 or 400 mg EDU L-1 (in two separate experiments). We found that EDU per se had no effects on plants exposed to AOZ. EOZ practically significantly injured S. sachalinensis plants, and the impact was indifferent between the experiments. EDU did not protect plants against EOZ impact when applied as soil drench but it did protect them when applied as 200-400 mg.L-1 foliar spray. We conclude that EDU may be. more effective against O-3 phytotoxicity to fast-growing species when applied as a spray than when applied as a drench. Key message: Soil-drenched EDU was ineffective in protecting willow plants against O-3-induced injury, whereas foliar-sprayed EDU was effective even at the concentration of 200 mg L-1. (C) 2016 Elsevier B.V. All rights reserved

Ethylenediurea (EDU) as a protectant of plants against O₃

Ethylenediurea (EDU) is an anti-ozonant substance that is recognized as a versatile research tool, and　recently attracts increasing interest. As many wild plant species are forced into complex responses by tropospheric ozone (O3), these responses are crucial for the functioning of ecosystems and consequently for the biosphere; thus, countermeasures are required. A plethora of substances have been evaluated as to their effectiveness in protecting plants against O3. EDU is the most widely-used substance in O3 research, in order to moderate O3 effects on plant growth. We present a synoptic table with recent literature on EDU applications to plants as a protectant against O3. This table summarizes important information on these publications, and we hope to be usefull to researchers intended to employ EDU in their research with wild plants, but also to researchers working with air pollution control and other scientists

High doses of ethylene diurea (EDU) are not toxic to willow and act as nitrogen fertilizer

Ethylene diurea (EDU) is synthetic chemical which protects plants against damage caused by ground level O-3 and is used experimentally as a biomonitoring tool at doses usually ranging from 200 to 400 mg L-1 a.i. Although several studies have investigated the protective action of EDU, this mechanism remains unclear. Important uncertainties in EDU action are whether EDU acts as a source of nitrogen (N) to plants and whether high doses are phytotoxic. In order to answer these questions, we conducted an open-field experiment where potted willow (Salix sachalinensis Fr. Schm) plants were exposed to ambient O-3 conditions and treated with 0, 800 or 1600 mg L-1 EDU as a soil drench, every nine days, for about 2.5 months. We examined approximately 50 response variables. Based on N content in different plant organs, we found that (a) all EDU was transferred to the leaves and (b) high doses of EDU increased the leaf N content. However, EDU did not affect the C content and distribution within the plant body. Still, even at the highest dose, EDU was not toxic to this fast-growing species (however such a high dose should not be applied in uncontrolled environments); and there was no EDU persistence in the soil, as indicated by soil N content. Notably, our soil was free from organic matter and N-poor. Key message: EDU per se does not cause toxicity to willow plants when applied as drench to a soil with no organic matter, rather, high EDU doses may act as nitrogen fertilizer in a nitrogen-poor soil. (C) 2016 Elsevier B.V. All rights reserved