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Το φαινόμενο της όρμησης στην τοξικολογία (Hormesis phenomenon in Toxicology)

Book Chapter
Αγαθοκλέους Ε., Μαρκουίζου Α., Σαϊτάνης Κ.Ι. (Agathokleous E., Markouizou A., Saitanis C.J.)
Κεφάλαιο 6. Στο: Τσατσάκης Α. Τοξικολογία στο σύγχρονο κόσμο. Ιατρικές Εκδόσεις Νέον. (Chapter 6. In: Tsatsakis A. Toxicology in the modern world. Publisher: Medical Editions Neon ISBN: 978-618-84478-0-6
Publication year: 2020

Plant susceptibility to ozone: A Tower of Babel? 

Journal Paper
Agathokleous, E. and Saitanis, C.J., 
Science of the Total Environment,Volume 703, 134962
Publication year: 2020

Abstract

In a world with climate change and environmental pollution, modern Biology is concerned with organismic susceptibility. At the same time, policy and decision makers seek information about organismic susceptibility. Therefore, information about organismic susceptibility may have far-reaching implications to the entire biosphere that can extend to several forthcoming generations. Here, we review a sample of approximately 200 published peer-reviewed articles dealing with plant response to ground-level ozone to understand how the information about susceptibility is communicated. A fuzzy and often incorrect terminology was used to describe the responsiveness of plants to ozone. Susceptibility was classified too arbitrarily and this was reflected to the approximately 50 descriptive words that were used to characterize susceptibility. The classification of susceptibility was commonly based on calculated probability (p) value. This practice is inappropriate as p values do not provide any basis for effect or susceptibility magnitude. To bridge the gap between science and policy decision making, classification of susceptibility should be done using alternative approaches, such as effect size estimates in conjunction with multivariate ordination statistics.

Ozone Effects on Vegetation: A Walk from Cells to Ecosystems

Book Chapter
Burkey K.O., Agathokleous E., Saitanis C.J., Mashaheet A. M. , Koike T. and Hung Y.-T.
Chapter 10. Ozone Effects on Vegetation: A Walk from Cells to Ecosystems. In: Hung, Y.T., Wang, L.K., and N. Shammas eds. Handbook of Environment and Waste Management, Volume 3: Acid Rain and Greenhouse Gas Pollution Control, pp. 357-396 (ISBN-10: 9811207127). World Scientific Publishing Co. Inc, Singapore, 14 August 2020. DOI: 10.1142/9789811207136_0010
Publication year: 2020

Ozone biomonitoring: A versatile tool for science, education and regulation

Journal Paper
Agathokleous E., Saitanis C.J., Feng Z., De Marco A., Araminiene V., Domingos M., Sicard P., Paoletti E.
Current Opinion in Environmental Science & Health, 18:7-13
Publication year: 2020

Abstract

Ground-level ozone (O3) pollution can adversely affect human health and vegetation, thus being an important environmental issue nowadays. Ozone biological monitoring (biomonitoring) is a method of O3 monitoring by observing quantitative changes in living organisms physically present in a specific environment. Here, we provide a concise view of the field of O3 biomonitoring, along with recent advances that are expected to advance this field in the future. We also recommend that O3 biomonitoring is included in citizen science initiatives as well as in worldwide curricula of educational institutions. Policy-makers and general public may not understand biomonitoring data; hence, a major challenge is how to communicate the information to the audience in a way that permits the best comprehension.

Ozone affects plant, insect and soil microbial communities and threatens terrestrial ecosystems and biodiversity

Journal Paper
Agathokleous E., Feng Z., Oksanen E., Sicard P., Qi Wang1, Saitanis C.J.,  Araminiene V., Blande J.D., Hayes F., Calatayud V., Domingos M., Veresoglou S., Peñuelas J., Wardle D.A., De Marco A., Li Z., Harmens H., Yuan X., Vitale M., Kreft H., Sala O.E., Paoletti E
Science Advances, Vol. 6, no. 33, eabc1176 DOI: 10.1126/sciadv.abc1176
Publication year: 2020

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.

On the atmospheric ozone monitoring methodologies

Journal Paper
Saitanis J.C., Sicard P., De Marco A., Feng Z., Paoletti E., Agathokleous E.
Current Opinion in Environmental Science & Health, Volume 18, Pages 40-46
Publication year: 2020

Ozone (O3) is a natural component of the atmosphere. It occurs in the stratosphere, where it protects biota against ultraviolet radiation, but also in the lower troposphere, where it can directly harm biota. Because of its (i) high toxicological potential for biota, (ii) high reactivity and molecular instability, and (iii) difficult differentiation from other reactive oxygen species, O3 challenges scientists in a continuing effort to develop methods for its monitoring. We present here the operation principles of the most used techniques, along with some new technological developments for atmospheric O3 monitoring, with emphasis upon near surface. Huge amounts of scientific data have been produced thanks to progresses in O3 monitoring technologies. However, it remains a challenge to further develop reliable methods with rapid response and high sensitivity to ambient O3, which will also be free from the disadvantages of the current technologies.

Ground-Level Ozone Profile and the Role of Plants as Sources and Sinks

Book Chapter
Saitanis, C.J., Agathokleous, E., Burkey, K., and Hung, Y.T.
Chapter 8. In: Hung, Y.T., Wang, L.K., and N. Shammas eds. Handbook of Environment and Waste Management, Volume 3: Acid Rain and Greenhouse Gas Pollution Control, pp. 281-324. (ISBN-10: 9811207127). World Scientific Publishing Co. Inc, Singapore, 14 August 2020. DOI: 10.1142/9789811207136_0008
Publication year: 2020

Ambient Ozone Alternative Monitoring And Biomonitoring With Higher Plants

Book Chapter
Saitanis C.J., Burkey K.O., Agathokleous E., and Hung Y.-T.
Chapter 9. In: Hung, Y.T., Wang, L.K., and N. Shammas eds. Handbook of Environment and Waste Management, Volume 3: Acid Rain and Greenhouse Gas Pollution Control, pp. 325-356 (ISBN-10: 9811207127). World Scientific Publishing Co. Inc, Singapore, 14 August 2020. DOI: 10.1142/9789811207136_0009
Publication year: 2020

Study of the effect of different rootstocks on the growth and production of beans grown under increased salinity conditions

National Conference
Vougelekas V., Datsi G., Mylonas F., TabakakiA., Saitanis K.I., Savvas D.
Scientific Conference of EEEO. Research Applications and Leading Technologies in Plant Production. Patras 15-18 Oct. 2019. Book of Abstracts, p. 211
Publication year: 2019

Stress response and population dynamics: Is Allee effect hormesis?

Journal Paper
Saitanis C.J., and Agathokleous E.
Science of the Total Environment, 682, pp. 623-628
Publication year: 2019

Abstract

Hormesis is a fundamental notion in ecotoxicology while competition between organisms is an essential notion in population ecology and species adaptation and evolution. Both sub-disciplines of ecology deal with the response of organisms to abiotic and biotic stresses. In ecotoxicology, the Linear-non-Threshold (LNT), Threshold and Hormetic models are used to describe the dominant responses of a plethora of endpoints to abiotic stress. In population ecology, the logistic, theta-logistic and the Allee effect models are used to describe the growth of populations under different responses to (biotic) stress induced by population density. The per capita rate of population increase (r) measures species fitness. When it is used as endpoint, the responses to population density seem to perfectly correspond to LNT, Threshold and Hormetic responses to abiotic stress, respectively. Our analysis suggests the Allee effect is a hormetic-like response of r to population density, an ultimate biotic stress. This biphasic dose-response model appears across different systems and situations (from molecules to tumor growth to population dynamics), is highly supported by ecological and evolutionary theory, and has important implications in most sub-disciplines of biology as well as in environmental and earth sciences. Joined multi-disciplinary efforts would facilitate the development and application of advanced research approaches for better understanding potential planetary-scale implications.

Predicting the effect of ozone on vegetation via the linear non-threshold (LNT), threshold and hormetic dose-response models

Journal Paper
Agathokleous, E., Belz, R.G., Calatayud, V., De Marco, A., Hoshika, Y., Kitao, M., Saitanis, C.J., Sicard, P., Paoletti, E., Calabrese, E.J.
Science of the Total Environment 649: 61-74.
Publication year: 2019

Abstract

The nature of the dose-response relationship in the low dose zone and how this concept may be used by regulatory agencies for science-based policy guidance and risk assessment practices are addressed here by using the effects of surface ozone (O3) on plants as a key example for dynamic ecosystems sustainability. This paper evaluates the current use of the linear non-threshold (LNT) dose-response model for O3. The LNT model has been typically applied in limited field studies which measured damage from high exposures, and used to estimate responses to lower concentrations. This risk assessment strategy ignores the possibility of biological acclimation to low doses of stressor agents. The upregulation of adaptive responses by low O3 concentrations typically yields pleiotropic responses, with some induced endpoints displaying hormetic-like biphasic dose-response relationships. Such observations recognize the need for risk assessment flexibility depending upon the endpoints measured, background responses, as well as possible dose-time compensatory responses. Regulatory modeling strategies would be significantly improved by the adoption of the hormetic dose response as a formal/routine risk assessment option based on its substantial support within the literature, capacity to describe the entire dose-response continuum, documented explanatory dose-dependent mechanisms, and flexibility to default to a threshold feature when background responses preclude application of biphasic dose responses.

Effects of ozone and ammonium sulfate on cauliflower: emphasis on the interaction between plants and insect herbivores

Journal Paper
Agathokleous, E., WaiLi,  Y., Ntatsi, G., Konno, K., Saitanis, C.J., Kitao, M., and Koike, T.
 Science of the Total Environment 659: 995-1007
Publication year: 2019

Abstract

Ammonium sulfate [(NH4)2SO4] deposition and elevated ozone (O3) concentrations may negatively affect plants and trophic interactions. This study aimed to evaluate for the first time the interactive effects of high (NH4)2SO4 load and elevated O3 levels on cauliflower (Brassica oleracea L.) under field conditions. Cauliflower seedlings were treated with 0 (AS0) or 50 (AS50) kg ha−1 (NH4)2SO4 and exposed to ambient (AOZ, ≈20 ppb) or elevated (EOZ, ≈55 ppb) O3 for about one month, in a Free Air O3 Concentration Enrichment (FACE) system. The oligophagous diamondback moth (Plutella xylostella Linnaeus, 1758) showed a clear preference towards the seedlings treated with AS50, which intensively grazed. Plant-herbivore interactions were driven by (NH4)2SO4 availability, rather than O3, via increased nitrogen content in the leaves. Further laboratory bioassays were followed to confirm the validity of these observations using polyphagous Eri silkmoth larvae (Samia ricini) as a biological model in a standardized experimental setup. Choice assays, where larvae could select leaves among leaf samples from the different experimental conditions, and no-choice assays, where larvae could graze leaves from just one experimental condition, were conducted. In the choice assay, the larvae preferred AS50-treated leaves, in agreement with the field observations with diamondback moth. In the no-choice assay, larval body mass growth was inhibited when fed with leaves treated with EOZ and/or AS50. Larvae fed with AS50-treated leaves displayed increased mortality. These observations coincide with higher NO3 and Zn content in AS50-treated leaves. This study shows that plant-herbivore interactions can be driven by (NH4)2SO4 availability, independently of O3, and suggests that high N deposition may have severe health implications in animals consuming such plant tissues.

Key message: Plant-herbivore interactions are driven by high (NH4)2SO4 availability, independently of O3.

Effect of grafting on growth, production and biological nitrogen binding of Greek bean varieties

National Conference
Vougeleka V., Datsi G., Panagiotakis I., TabakakiA., Saitanis K.I., Savvas D.
Scientific Conference of EEEO. Research Applications and Leading Technologies in Plant Production. Patras 15-18 Oct. 2019. Book of Abstracts, p. 103
Publication year: 2019

Commentary: EPA’s proposed expansion of dose-response analysis is a positive step towards improving its ecological risk assessment

Journal Paper
Agathokleous, E., Anav, A., Araminiene, V., De Marco, A., Domingos, M., Kitao, M., Koike, T., Manning, W.J., Paoletti, E., Saitanis, C.J., Sicard, P., Vitale, M., Wang, W., and Calabrese, E.J.
Environmental Pollution 246: 566-570
Publication year: 2019

Abstract

The United States Environmental Protection Agency (US EPA) has recently proposed changes to strengthen the transparency of its pivotal regulatory science policy and procedures. In this context, the US EPA aims to enhance the transparency of dose-response data and models, proposing to consider for the first time non-linear biphasic dose-response models. While the proposed changes have the potential to lead to markedly improved ecological risk assessment compared to past and current approaches, we believe there remain open issues for improving the quality of ecological risk assessment, such as the consideration of adaptive, dynamic and interactive effects. Improved risk assessment including adaptive and dynamic non-linear models (beyond classic threshold models) can enhance the quality of regulatory decisions and the protection of ecological health. We suggest that other countries consider adopting a similar scientific-regulatory posture with respect to dose-response modeling via the inclusion of non-linear biphasic models, that incorporate the dynamic potential of biological systems to adapt (i.e., enhancing positive biological endpoints) or maladapt to low levels of stressor agents.

A quantitative assessment of hormetic responses of plants to ozone

Journal Paper
Agathokleous, E., Araminiene, V., Belz, R.G., Calatayud, V., De Marco, A., Domingos, M., Feng, Z., Hoshika, Y., Kitao, M., Koike, T., Paoletti, E., Saitanis, C.J., Sicard, P., Calabrese, E.J.
Environmental Research, 176, art. no. 108527.
Publication year: 2019

Abstract

Evaluations of ozone effects on vegetation across the globe over the last seven decades have mostly incorporated exposure levels that were multi-fold the preindustrial concentrations. As such, global risk assessments and derivation of critical levels for protecting plants and food supplies were based on extrapolation from high to low exposure levels. These were developed in an era when it was thought that stress biology is framed around a linear dose-response. However, it has recently emerged that stress biology commonly displays non-linear, hormetic processes. The current biological understanding highlights that the strategy of extrapolating from high to low exposure levels may lead to biased estimates. Here, we analyzed a diverse sample of published empirical data of approximately 500 stimulatory, hormetic-like dose-responses induced by ozone in plants. The median value of the maximum stimulatory responses induced by elevated ozone was 124%, and commonly <150%, of the background response (control), independently of species and response variable. The maximum stimulatory response to ozone was similar among types of response variables and major plant species. It was also similar among clades, between herbaceous and woody plants, between deciduous and evergreen trees, and between annual and perennial herbaceous plants. There were modest differences in the stimulatory response between genera and between families which may reflect different experimental designs and conditions among studies. The responses varied significantly upon type of exposure system, with open-top chambers (OTCs) underestimating the maximum stimulatory response compared to free-air ozone-concentration enrichment (FACE) systems. These findings suggest that plants show a generalized hormetic stimulation by ozone which is constrained within certain limits of biological plasticity, being highly generalizable, evolutionarily based, and maintained over ecological scales. They further highlight that non-linear responses should be taken into account when assessing the ozone effects on plants.

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