Assessment of Ethylene Diurea-Induced Protection in Plants Against Ozone Phytotoxicity

Abstract

Urbanization, industrialization and unsustainable utilization of natural resources have made tropospheric ozone (03) one of the world's most significant air pollutants. Past studies reveal that 0 3 is a phytotoxic air pollutant that causes or enhances food insecurity across the globe. Plant sensitivity, tolerance and resistance to 0 3 involve a wide array of responses that range from growth to the physiological, biochemical and molecular. Although plants have an array of defense systems to combat oxidative stress from 0 3 exposure, they still suffer sizable yield reductions. In recent years, the ground-level 0 3 concentrations to which crop plants have been exposed have caused yield loses that are economically damaging. Several types of chemicals have been applied or used to mitigate the effects produced by 0 3 on plants. These include agrochemicals (fungicides, insecticides, plant growth regulators), natural antioxidants, and others. Such treatments have been effective to one degree to another, in ameliorating Or generated stress in plants. Ethylene diurea (EDU) has been the most effective protectant used and has also served as a monitoring agent for assessing plant yield losses from 0 3 exposure. In this review, we summarize the data on how EDU has been used, the treatment methods tested, and application doses found to be both protective and toxic in plants. We have also summarized data that address the nature and modes of action (biophysical and biochemical) of EDU. In general, the literature discloses that EDU is effective in reducing ozone damage to plants, and indicates that EDU should be more widely used on 0 3 sensitive plants as a tool for biomonitoring of 0 3 concentrations. Biomonitoring studies that utilize EDU are very useful for rural and remote areas and in developing countries where 0 3 monitoring is constrained from unavailability of electricity. The mechanism(s) by which EDU prevents 0 3 toxicity in plants is still not completely known. EDU possesses great utility for screening plant sensitivity under field conditions in areas that experience high 0 3 concentrations, because EDU prevents 0 3 toxicity only in 0 3 sensitive plants. Ozone-resistant plants do not respond positively to EDU applications. However, EDU application dose and frequency must be standardized before it can be effectively and widely used for screening 0 3 sensitivity in plants. EDU acts primarily by enhancing biochemical plant defense and delaying Or induced senescence, thereby reducing chlorophyll loss, and maintaining physiological efficiency and primary metabolites; these actions enhance growth, biomass and yield of plants. We believe that future studies are needed to better address the EDU dose response relationship for many plant species, and to screen for new cultivars that can resist 0 3 stress. Although some research on the physiological and biochemical mechanisms of action of EDU have been performed, the new 'omics' tools have not been utilized to evaluate EDUs mechanism of action. Such data are needed, as is gene exp...

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

“…The harvest was done at the end of the growing season when plants stopped producing new leaves and, therefore, cannot be proved if plants treated with spray of 200 and 400 mg EDU L -1 compensated the accelerated leaf senescence by producing more leaves during the growing season (Kolb and Matyssek 2001). The reviews by Paoletti et al (2009) and Singh et al (2015) suggested that EDU delays the O 3 -induced accelerated senescence and this coincides with the findings of the present study. However, the fact that EDU soil drench protected against EOZ-induced accelerated senescence while did not protect against EOZ damage to all the other response variables (which are not related to the leaf number) indicates that either the EDU mode of action in protecting against O 3 injury is not upon protecting against O 3 -accelerated senescence -which is in agreement with suggestions by Eckardt and Pell (1996)-or EDU protection against EOZ injury was not completeas reported also by Paoletti et al (2007).…”

“…200-400 mg L -1 (Paoletti et al 2009, Feng et al 2010. EDU has been studied as a protectant of plants against O 3 , as an O 3 biomonitoring tool or as a comparative tool for screening other chemicals as to their efficacy to protect plants against O 3 impact (Paoletti et al 2009;Feng et al 2010;Manning et al 2011;Agathokleous et al 2015b;Singh et al 2015). EDU has been applied to plenty of agricultural crops.…”

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

“…More than 100 research articles about EDU role in plants exist in Science Citation Index (Thomson Reuters Co., New York). The mechanism through which EDU protects plants against O 3 injury has not been elucidated yet (Agathokleous, 2017;Agathokleous et al, 2015;Manning et al, 2011a;Oksanen et al, 2013;Paoletti et al, 2009;Singh et al, 2015).…”

“…It remains unknown if EDU high doses would contribute with N and cause toxicity when the plants have relatively large leaf area and the soil does not lack N, and this is an important issue (Agathokleous et al, 2015;Manning et al, 2011b;Singh et al, 2015). One important aspect is that EDU amounts in soil may vary over time, when EDU is applied as soil drench, because EDU may be adsorbed onto soil organic matter and released gradually through resolubilization by irrigation water, thereby potentially leading to greater amounts in the soil than the applied ones at random times (Pasqualini et al, 2016).…”

Assessing ambient ozone injury in olive (Olea europaea L.) plants by using the antioxidant ethylenediurea (EDU) in Saudi Arabia

“…There is a prevalent indication that EDU does not modify the stomatal conductance of plants in comparison with non-EDU treatment, suggesting that antiozonant activity of EDU is biochemical rather than biophysical in nature (Feng et al 2010), but conclusive proof of the intimate bases for the protective action remains elusive, and the mode of action of EDU remains disputed or unconfirmed. However-whatever its mode of action-EDU is a reliable, low-cost, and low-technology efficient tool for assessing O 3 effects on plant performances in the field, when EDU-treated and EDUuntreated individuals are exposed to ambient air in the presence of O 3 (Singh et al 2014). This is the first report dealing with EDU applications to olive trees (Feng et al 2010), and the main objective of this study was to evaluate the use of EDU as a possible, efficient, cost-effective tool to estimate O 3 effects on olive plants (Olea europaea L. cultivar Kalamata) under field conditions in an area subjected to relevant ambient O 3 pressure.…”