Effects Of Ethylenediurea Research Articles

Soil Microbial Community Involved in Nitrogen Cycling in Rice Fields Treated with Antiozonant under Ambient Ozone.

Ethylenediurea (EDU) can effectively mitigate the crop yield loss caused by ozone (O3), a major, phytotoxic air pollutant. However, the relevant mechanisms are poorly understood, and the effect of EDU on soil ecosystems has not been comprehensively examined. In this study, a hybrid rice variety (Shenyou 63) was cultivated under ambient O3 and sprayed with 450 ppm EDU or water every 10 days. Real time quantitative polymerase chain reaction (RT-qPCR) showed that EDU had no significant effect on the microbial abundance in either rhizospheric or bulk soils. By applying both metagenomic sequencing and the direct assembly of nitrogen (N)-cycling genes, EDU was found to decrease the abundance of functional genes related to nitrification and denitrification processes. Moreover, EDU increased the abundance of genes involved in N-fixing. Although the abundance of some functional genes did not change significantly, nonmetric multidimensional scaling (NMDS) and a principal coordinates analysis (PCoA) suggested that the microbial community structure involved in N cycling was altered by EDU. The relative abundances of nifH-and norB-harboring microbial genera in the rhizosphere responded differently to EDU, suggesting the existence of functional redundancy, which may play a key role in sustaining microbially mediated N-cycling under ambient O3. IMPORTANCE Ethylenediurea (EDU) is hitherto the most efficient phytoprotectant agent against O3 stress. However, the underlying biological mechanisms of its mode of action are not clear, and the effects of EDU on the environment are still unknown, limiting its large-scale application in agriculture. Due to its sensitivity to environmental changes, the microbial community can be used as an indicator to assess the environmental impacts of agricultural practices on soil quality. This study aimed to unravel the effects of EDU spray on the abundance, community structure, and ecological functions of microbial communities in the rhizosphere of rice plants. Our study provides a deep insight into the impact of EDU spray on microbial-mediated N cycling and the structure of N-cycling microbial communities. Our findings help to elucidate the mode of action of EDU in alleviating O3 stress in crops from the perspective of regulating the structure and function of the rhizospheric soil microbial community.

Ethylenediurea reduces grain chalkiness in hybrid rice cultivars under ambient levels of surface ozone in China.

High concentration of tropospheric ozone (O3) causes crop yield losses, which could be reduced by foliar application of ethylenediurea (EDU). Rice grain appearance is a major quality trait that determines the milling quality, white rice productivity and the market value. Grain chalkiness is one of the common defects that deteriorate the grain appearance in rice due to its negative effects on palatability and milling yield. Whether EDU could reduce grain chalkiness in rice which was usually increased by high concentration of O3 is not clarified. We report the grain chalkiness in 19 rice cultivars (CVs) of three types: indica (6 CVs), japonica (5 CVs) and hybrids (8 CVs), observed in an EDU application experiment in the field in China. The ambient O3 level as expressed by accumulated hourly O3 concentration over the threshold of 40 ppb (AOT40) for 80 days until maturity reached 12.8 ppm h at a near-by monitoring station. Fraction of the chalky grains (FCG) in the hybrid cultivars was 8% lower in EDU than that in the control treatments, whereas no significant effect of EDU on FCG was found in japonica or indica cultivars. The reduction of FCG due to EDU treatment in hybrid cultivars was attributed to the significant reduction of milky white grains followed by that of white belly grains. Thus, the application of EDU could ameliorate the decline of grain appearance quality in hybrid rice by decreasing the FCG and enhancing the fraction of perfect grains (FPG). Moreover, there were significant interactions between the EDU application and rice cultivars, indicating varietal difference in the protection of grain appearance quality by EDU. These results suggest the need for further studies on the mechanisms of the effects of EDU on grain chalkiness.

Ethylenediurea Reduces Grain Nitrogen but Enhances Protein and Carbon Yield in Rice Cultivars

Ethylenediurea (EDU) is an indicator of surface ozone (O3), has a high potential to be developed as an applicable protectant for crops against O3 phytotoxicity. Studies on the effects of EDU on grain quality are few, limiting evaluation of the efficiency of EDU protection. In order to understand the effects of EDU on grain quality in rice, a field study was conducted in a rice paddy, where EDU solutions were foliar applied to rice plants. At maturity, grain nitrogen concentrations (GN) in 21 rice cultivars and related traits were analyzed. Mean across 21 cultivars, GN was reduced by EDU by 3.81%, suggesting that O3 in ambient air is affecting grain quality. GN negatively correlated with grain weight and source/sink ratio, but positively correlated with spikelet density. Moreover, GN changes to EDU were rice type dependent, which were −0.43%, −0.72%, and 1.19% in indica, japonica, and hybrid rice, respectively. These results suggest that EDU promotes sink in rice, which helps to increase grain yield, but allocation of nitrogen is not enough to maintain GN in both indica and japonica cultivars. Rice types and cultivars’ variations in the responses of GN to EDU highlight a possibility to adjust grain quality by EDU, combining cultivar selection and agricultural management in response to surface O3 pollution.

Ethylenediurea (EDU) effects on hybrid larch saplings exposed to ambient or elevated ozone over three growing seasons

Ground-level ozone (O3) pollution is a persistent environmental issue that can lead to adverse effects on trees and wood production, thus indicating a need for forestry interventions to mediate O3 effects. We treated hybrid larch (Larix gmelinii var. japonica × L. kaempferi) saplings grown in nutrient-poor soils with 0 or 400 mg L−1 water solutions of the antiozonant ethylenediurea (EDU0, EDU400) and exposed them to ambient O3 (AOZ; 08:00 − 18:00 ≈ 30 nmol mol−1) or elevated O3 (EOZ; 08:00 − 18:00 ≈ 60 nmol mol−1) over three growing seasons. We found that EDU400 protected saplings against most effects of EOZ, which included extensive visible foliar injury, premature senescence, decreased photosynthetic pigment contents and altered balance between pigments, suppressed gas exchange and biomass production, and impaired leaf litter decay. While EOZ had limited effects on plant growth (suppressed stem diameter), it decreased the total number of buds per plant, an effect that was not observed in the first growing season. These results indicate that responses to EOZ might have implications to plant competitiveness, in the long term, as a result of decreased potential for vegetative growth. However, when buds were standardized per unit of branches biomass, EOZ significantly increased the number of buds per unit of biomass, suggesting a potentially increased investment to bud development, in an effort to enhance growth potential and competitiveness in the next growing season. EDU400 minimized most of these effects of EOZ, significantly enhancing plant health under O3-induced stress. The effect of EDU was attributed mainly to a biochemical mode of action. Therefore, hybrid larch, which is superior to its parents, can be significantly improved by EDU under long-term elevated O3 exposure, providing a perspective for enhancing afforestation practices.

Effects of ethylenediurea (EDU) on apoplast and chloroplast proteome in two wheat varieties under high ambient ozone: an approach to investigate EDU's mode of action.

Rising tropospheric ozone (O3) is a serious threat to plants and animals in the present climate change scenario. High tropospheric O3 has the capability to disrupt cellular organelles leading to impaired photosynthesis and significant yield reduction. Apoplast and chloroplast are two important cellular components in a plant system. Their proteomic response with ethylenediurea (EDU) treatment under tropospheric O3 has not been explored till date. EDU (an organic compound) protects plants exclusively against harmful O3 effects through activation of antioxidant defense mechanism. The present study investigated the mode of action of EDU (hereafter MAE) by identifying proteins involved in apoplast and chloroplast pathways. Two wheat varieties viz. Kundan and PBW 343 (hereafter K and P respectively) and three EDU treatments (0= control, 200, and 300 ppm) have been used for the study. In apoplast isolates, proteins such as superoxide dismutase (SOD), amino methyltransferase, catalase, and Germin-like protein have shown active role by maintaining antioxidant defense system under EDU treatment. Differential expression of these proteins leads to enhanced antioxidative defense mechanisms inside and outside the cell. Chloroplast proteins such as Rubisco, Ferredoxin NADP- reductase (FNR), fructose,1-6 bis phosphatase (FBPase), ATP synthase, vacuolar proton ATPase, and chaperonin have regulated their abundance to minimize ozone stress under EDU treatment. After analyzing apoplast and chloroplast protein abundance, we have drawn a schematic representation of the MAE working mechanism. The present study showed that plants can be capable of O3 tolerance, which could be improved by optimizing the apoplast ROS pool under EDU treatment.

Effects of ethylenediurea (EDU) on regulatory proteins in two maize (Zea mays L.) varieties under high tropospheric ozone phytotoxicity

Rising tropospheric ozone is a major threat to the crops in the present climate change scenario. To investigate the EDU induced changes in proteins, two varieties of maize, the SHM3031 and the PEHM5, (hereafter S and P respectively) were treated with three EDU applications (0= control, 50 and 200 ppm) (hereafter 0= A, 1 and 2 respectively) (SA, S1, S2, PA, P1, P2 cultivar X treatments). Data on the morpho-physiology, enzymatic activity, and protein expression (for the first time) were collected at the vegetative (V, 45 DAG) and flowering (F, 75 DAG) developmental stages. The tropospheric ozone was around 53 ppb enough to cause phytotoxic effects. Protective effects of EDU were recorded in morpho-physiologically and biochemically. SOD, CAT and APX together with GR performed better under EDU protection in SHM3031 variety than PEHM5. The protein expression patterns in SHM3031 at the vegetative stage (28% proteins were increased, 7% were decreased), and at the flowering stage (17% increased, 8% decreased) were found. In PEHM5, a 14% increase and an 18% decrease (vegetative stage) whereas a 16% increase and a 20% decrease (flowering stage) were recorded in protein expression. Some protein functional categories, for instance, photosynthesis, carbon metabolism, energy metabolism, and defense were influenced by EDU. Rubisco expression was increased in SHM3031 whereas differentially expressed in PEHM5. Germin like protein, APX, SOD, and harpin binding proteins have enhanced defense regulatory mechanisms under EDU treatment during prevailing high tropospheric O3. The present study showed EDU protective roles in C4 plants as proven in C3.

Ethylenediurea (EDU) mitigates the negative effects of ozone in rice: Insights into its mode of action.

Monitoring of ozone damage to crops plays an increasingly important role for the food security of many developing countries. Ethylenediurea (EDU) could be a tool to assess ozone damage to vegetation on field scale, but its physiological mode of action remains unclear. This study investigated mechanisms underlying the ozone-protection effect of EDU in controlled chamber experiments. Ozone sensitive and tolerant rice genotypes were exposed to ozone (108ppb, 7hrday-1 ) and control conditions. EDU alleviated ozone effects on plant morphology, foliar symptoms, lipid peroxidation, and photosynthetic parameters in sensitive genotypes. Transcriptome profiling by RNA sequencing revealed that thousands of genes responded to ozone in a sensitive variety, but almost none responded to EDU. Significant interactions between ozone and EDU application occurred mostly in ozone responsive genes, in which up-regulation was mitigated by EDU application. Further experiments documented ozone degrading properties of EDU, as well as EDU deposits on leaf surfaces possibly related to surface protection. EDU application did not mitigate the reaction of plants to other abiotic stresses, including iron toxicity, zinc deficiency, and salinity. This study provided evidence that EDU is a surface protectant that specifically mitigates ozone stress without interfering directly with the plants' stress response systems.

Responses of Zea mays L. cultivars ‘Buland’ and ‘Prakash’ to an antiozonant ethylene diurea grown under ambient and elevated levels of ozone

Increase in surface level of ozone (O3) in last 30 years is one of the major problems for global agriculture. Field experiment was conducted using open top chambers on two Indian maize cultivars (Buland and Prakash) grown under ambient (AO) and elevated (EO) O3 concentrations to evaluate the effect of an antiozonant ethylene diurea (EDU) given as soil drench. EDU application reduced the ROS production with concomitant decrease in lipid peroxidation. Inductions in activities of enzymatic antioxidants along with increased content of non-enzymatic antioxidants were observed in EDU-treated plants, though the response varied between the cultivars. Photosynthetic proteins (PEP carboxylase and RuBisCO large and small subunits) detected through SDS–PAGE analysis increased with EDU treatment. EDU also led to an increase in jasmonic acid and a decline in salicylic acid contents. The protective effect of EDU was further accompanied by increased pigments (chlorophyll and carotenoids), foliar carbohydrates (starch and total soluble sugars), enhanced biomass, and economic yield. Effectiveness of EDU was more evident at higher O3 concentration and cultivar Prakash exhibited a more positive response with EDU as compared to Buland.

Effects of the Antiozonant Ethylenediurea (EDU) on Fraxinus ornus L.: The Role of Drought

Ethylenediurea (EDU) is a synthetic chemical known to protect plants from the phytotoxic effects of tropospheric ozone (O3). Although many studies have proposed the use of EDU for studying the O3 effects under field conditions, its mechanism of action is not fully understood, and it is unclear whether it exerts a specific antiozonant action, or if it may also interact with other oxidative stresses. The aim of this work was to evaluate the effect of EDU on forest species in a Mediterranean environment where, during summer, vegetation is exposed to multiple oxidative stresses, such as O3 and drought. The experiment was conducted on Fraxinus ornus L. (Manna ash) plants growing in six mesocosms, three maintained under full irrigation, while the other three were subjected to drought for 84 days. In each mesocosm, three plants were sprayed every 15 days with 450 ppm EDU. Gas exchange and chlorophyll “a” fluorescence measurements carried out through the experimental period highlighted that EDU did not affect stomatal conductance and had an ameliorative effect on the functionality of drought-stressed plants, thus suggesting that it may act as a generic antioxidant. The implications of these findings for the applicability of EDU in field studies are discussed.

Ethylenediurea as a potential tool in evaluating ozone phytotoxicity: a review study on physiological, biochemical and morphological responses of plants.

Present-day climate change scenario has intensified the problem of continuously increasing ground-level ozone (O3), which is responsible for causing deleterious effects on growth and development of plants. Studies involving use of ethylenediurea (EDU), a chemical with antiozonant properties, have given some promising results in evaluating O3 injury in plants. The use of EDU is especially advantageous in developing countries which face a more severe problem of ground-level O3, and technical O3-induced yield loss assessment techniques like open-top chambers cannot be used. Recent studies have detected a hormetic response of EDU on plants; i.e. treatment with higher EDU concentrations may or may not show any adverse effect on plants depending upon the experimental conditions. Although the mode of action of EDU is still debated, it is confirmed that EDU remains confined in the apoplastic regions. Certain studies indicate that EDU significantly affects the electron transport chain and has positive impact on the antioxidant defence machinery of the plants. However, the mechanism of protecting the yield of plants without significantly affecting photosynthesis is still questionable. This review discusses in details the probable mode of action of EDU on the basis of available data along with the impact of EDU on physiological, biochemical, growth and yield response of plants under O3 stress. Data regarding the effect of EDU on plant 'omics' is highly insufficient and can form an important aspect of future EDU research.

Effects of a three-year exposure to ambient ozone on biomass allocation in poplar using ethylenediurea

We examined the effect of ambient ozone on visible foliar injury, growth and biomass in field-grown poplar cuttings of an Oxford clone sensitive to ozone (Populus maximoviczii Henry × berolinensis Dippel) irrigated with ethylenediurea (EDU) or water for three years. EDU is used as an ozone protectant for plants. Protective effects of EDU on ozone visible injury were found. As a result, poplar trees grown under EDU treatment increased leaves, lateral branches and root density in the third year, although no significant enhancement of stem height and diameter was found. Ambient ozone (AOT40, 24.6 ppm h; diurnal hourly average, 40.3 ppb) may finally reduce carbon gain by reducing the number of branches, and thus sites for leaf formation, in ozone-sensitive poplar trees under not-limiting conditions.

Effect of Ethylene Diurea on Oxygen-induced Ischemic Retinopathy in the Neonatal Rat

This study investigated the effect of N[2(2-oxo-1-imidazolidinyl) ethyl]-N-phenylurea (ethylene diurea, EDU) on oxygen-induced ischemic retinopathy (OIR) in a neonatal rat model. OIR was induced by maintaining daily cycles of 80% oxygen (20.5 h), ambient air (0.5 h), and a progressive return to 80% oxygen (3 h) for 12 days (postnatal day : P12). The rats were treated intraperitoneally with EDU (30 mg / kg body weight) or distilled water (DW) from P6 to P17. At P18, the percentage of avascular areas in the total retinal area (%AVA) was measured, and retinal neovascularization (NV) was scored in ADPase-stained retinas. Retinal superoxide dismutase (SOD) activity in the retina was also determined by a chemiluminescence method. The mean %AVA in the EDU-treated group (9.3±1.7%, n= 16) was lower than in the DW group (18.2 ± 4.7%, n = 17). EDU did not signi cantly affect NV, but significantly increased SOD activity (1.36±0.13 units / mg protein, n = 4) compared to DW treatment (1.04±0.01 units / mg protein, n = 4, P= 0.032) at P18. These results suggest that EDU treatment decreased the %AVA, accompanied by an increase in normal retinal vascular growth and / or a decrease in vessel proliferation. The increased SOD activity observed in the present study is likely to involve the EDU-mediated effects.

Ozone sensitivity and ethylenediurea protection in ash trees assessed by JIP chlorophyll a fluorescence transient analysis

The effect of ethylenediurea (EDU) was tested using the chlorophyll (Chl) a fluorescence transient analysis, performed with JIP-test, to assess ambient ozone (O3) effects on photosynthesis of adult trees under natural conditions. Twelve adult European ash (Fraxinus excelsior L.) trees, known to be sensitive or tolerant to O3, determined by presence symptomatic (S) or absence asymptomatic (AS) trees of foliar symptoms in previous years, were treated either with distilled water containing 450 g m-3 EDU or with distilled water. Once a month across the growing season [the accumulated exposure over a threshold of 40 nmol(O3) mol-1 was 32.49 µmol mol-1 h-1], Chl a fluorescence transients were measured in vivo on dark-adapted leaves of 1-year-old labeled shoots, from the lower crown part. Twenty-five parameters were calculated. The maximum quantum yield of primary photochemistry (ϕPo or Fv/Fm) did not differentiate between S-and AS-trees, while increased Chl content and de-excitation rates suggested compensation of O3 injury in S-trees. Seasonal reductions in absorbing fluxes and increase in heat and fluorescence dissipation processes was due to leaf ageing and drought, the latter suggesting water deficit influenced Chl a fluorescence stronger than ambient O3 exposure. AS-trees showed elevated probability of connectivity among photosystem 2 units, a mechanism to stimulate energy dissipation and reduce photo-oxidative injury. EDU prevented the inactivation of reaction centers. This slight effect does not warrant EDU as a tool to assess O3 effects on photosynthesis, while the JIP-test is suggested for a quantitative assessment in adult trees.

Factors affecting the effects of EDU on growth and yield of field-grown bush beans ( Phaseolus vulgaris L.), with varying degrees of sensitivity to ozone

The effects of foliar applications of ethylenediurea (EDU) on responses to ozone by field-grown bush bean ( Phaseolus vulgaris L.) lines ‘ S156’ (O 3-sensitive) and ‘ R123’ (O 3-tolerant), and cultivars ‘ BBL 290’ (O 3-sensitive) and ‘ BBL 274’ (O 3-tolerant) were investigated during the 2001 and 2002 growing seasons. EDU was applied weekly to designated plants between primary leaf expansion and pod senescence. Results were compared with control plants at harvests made at pod maturation and pod senescence. In 2001, average hourly ambient O 3 concentrations ranged between 41 and 59 ppb for a total of 303 h; in 2002, for 355 h. EDU applications prior to pod maturation significantly increased the number of marketable pods in ‘ R123’, but not for the other cultivars. Harvests at pod senescence showed significant improvements in crop yield production in EDU-treated ‘ S156’ plants, whereas for EDU-treated ‘ R123’ plants significant reductions were determined in above-ground biomass and seed production. In contrast, results from ‘ BBL 290’ and ‘ BBL 274’ at both harvest points were inconclusive. Growth and reproductive responses of O 3-sensitive and O 3-tolerant bush bean plants to EDU applications varied, depending on developmental stages, duration of EDU applications, and fluctuations in ambient O 3.

Effects of Ethylene diurea as a protective antiozonant on beans (Phaseolus vulgaris cv Lit) exposed to different tropospheric ozone doses in Catalonia (NE Spain)

A study to evaluate the effects of ethylene diurea (EDU) as a protective antiozonant for beans (Phaseolus vulgaris) submitted to different ambient ozone concentrations was performed in three stations of the rural Network for Air Quality Monitoring (Catalonia, NE Spain). The highest ozone concentrations were accompanied by significant reductions in fruit yield, number of fruits and shoot biomass. These reductions were lower in plants treated with EDU. The results showed toxic ozone effects on sensitive species such as beans and a protective antiozonant effect of EDU. The intensity of the EDU protective effect differed among the different stations characterised by different meteorological conditions and O3 concentrations.

Ethylene diurea (EDU) protection against ozone injury in tomato plants at Delhi.

Air pollution has become an increasingly serious problem in developing countries. Ozone is the most phytotoxic gaseous air pollutant. Ground level ozone measurements carried out at Delhi during 1990 -1992 show that the ambient concentration of ozone varies between 20 to 273 μg m , and the one hour WHO ozone standard of 110.74 μg m , was violated on many occasions (Varshney and Aggarwal, 1992). Heck et al., 1982 have shown that out of total crop loss caused by air pollution in USA, about 90% of the crop loss is attributed to ozone. Ethylene diurea (EDU) has been shown to be specific in protecting plants against ozone injury because it is an strong anti-oxidant (Carnahan et al., 1978). Exploratory studies have been carried out to evaluate the protective role of EDU against ozone damage in cereals, legumes and vegetables (Astorino et al., 1995; Brennan et al., 1990; Brunschon-Harti, 1995; Clarke et al., 1990; Hofstra et al., 1978; Kostaka-Rick and Manning, 1992, 1993; Tonneijck and Vandijk, 1997). In India Bambawale (1986) have shown that the leaf spot disease of potato reported from Punjab in 1978 was primarily due to ozone pollution and foliar spray of EDU was found to reduce about 25-30%leaf spot disease. Higher yield in EDU-treated plants in comparison to untreated plants has been attributed to the specific protective effect of EDU against ozone damage (Clarke et al., 1990; Saettler, 1981; Smith et al., 1987).

Effects of ambient ozone on injury and yield of Phaseolus vulgaris at four rural sites in the Netherlands as assessed by using ethylenediurea (EDU).

To assess adverse effects of ambient ozone on injury and yield, EDU (ethylenediurea) and non-EDU-treated plants of bean (Phaseolus vulgaris L. cv. Lit) were exposed to ambient air at four rural sites in the Netherlands in 1994. After 6 wk of exposure, the proportion of leaves injured in non-EDU-treated plants was higher than that in plants treated with the antioxidant. A maximal degree of 35 % injury was observed. The highest ozone levels accumulated at each site for three consecutive days before injury clearly exceeded the proposed short-term critical level for injury development. Both injury in untreated plants and the protective effect of EDU differed between sites and were not related to the measured ozone levels. EDU increased the d. wt of dry (mature) pods after 11 wk of exposure but not of green (marketable) pods after 6 wk. The effect of EDU in enhancing dry pod yield did not differ between sites and was 20% on average. The proportional yield increases in EDU-treated plants compared with those of non-EDU-treated plants at the sites were not correlated with the measured ozone levels known to adversely affect bean yield. The available evidence, however, suggests that ambient ozone was involved in the observed yield increase by EDU. When the dry pods were harvested, EDU-treated plants had more leaves than non-EDU-treated ones. The effect of EDU in delaying senescence appears to be an important factor to consider when attempting to evaluate the effect of ambient ozone on pod weight in beans using the EDU approach.

Effects of Ethylenediurea on Snap Bean at a Range of Ozone Concentrations.

Ethylenediurea (EDU) [N-[2-(2-Oxo-1-imidazolidinyl)ethyl]-N'-phenylurea] often protects plants from visible foliar injury due to the air pollutant O3 , and it has been used to demonstrate yield losses from O3 under field conditions. A few studies, however, have indicated that EDU can suppress plant growth and yield. Because of the potential value of EDU as a research and assessment tool, controlled field experiments with snap bean (Phaseolus vulgaris L. 'BBL-290') were performed to test the effectiveness of different EDU application rates across a range of O3 concentrations. Four O3 concentrations were used in open-top chambers in each of two experiments [charcoal-filtered (CF) air, nonfiltered (NF) air, and nominal O3 additions of 0.025 and 0.05 or 0.03 and 0.06 μL L-1 O3 to NF air]. Ethylenediurea was added biweekly to the potting medium (four applications per experiment) as a soil drench. The EDU treatment concentrations were 0, 14, 28, 56, and 120 and 0, 8, 16, and 32 mg EDU (active) L-1 of potting medium in experiments one and two, respectively. Ethylenediurea provided some protection against O3 -induced foliar injury and growth suppression in both experiments. Measurements of net carbon exchange rate (NCER) and carbohydrate status of the tissues reflected the protective effects of EDU. In the first experiment, however, EDU caused visible foliar injury at some growth stages and suppressed growth. In the second experiment, visible foliar injury was not caused by EDU at any concentration, but pod biomass (yield) was suppressed by EDU in CF chambers. The differences in response to EDU between the experiments may have been due to environmental conditions (i.e., hot and dry during the first experiment and cooler during the second). Ethylenediurea also affected biomass partitioning in the plants grown in CF air (relative biomass was increased in leaves and decreased in pods). The results indicate that although EDU does protect or partially protect snap bean against O3 injury, it may also affect physiology and growth.

Dose-response studies with the antiozonant ethylenediurea (EDU), applied as a soil drench to two growth substrates, on greenhouse-grown varieties of Phaseolus vulgaris L.

To study plant growth and yield effects of the antiozonant ethylenediurea (EDU), which is frequently used for ozone crop loss assessments, dose-response studies were carried out with potted bean plants under greenhouse conditions in winter and spring. Two cultivars of Phaseolus vulgaris L., differing in sensitivity to ozone (O 3), were grown in unfiltered air on a sandy loam rich in organic matter and on a vermiculite-clay mixture. Four treatments of EDU at concentrations from 300 to 800 mg liter −1 were given as a soil drench during plant development. Foliar symptoms of EDU phytoxicity were observed at all doses, and plant biomass, particularly pod dry weight, was considerably reduced to increasing doses of EDU. Primary and first trifoliate leaf weight in EDU-treated plants increased as did the number of buds, indicating an extension of vegetative growth and a delay of reproductive processes. ‘BBL 290’ beans, which are O 3-sensitive, were injured by EDU more than the O 3-tolerant ‘BBL 274’. The phytotoxic effects of EDU were more pronounced in the synthetic growth substrate than in field soil. In a second experiment, EDU was applied in concentrations from 100 to 400 mg liter −1 to ‘BBL 290’ plants, exposed to filtered air or simulated levels of O 3 pollution. In field soil, plant growth and biomass partitioning in filtered air was only slightly altered by EDU, although leaf injury due to EDU occured. In the vermiculite-clay mix, the biomass of most plant organs, particularly that of roots, was linearly reduced with increasing EDU doses. O 3 did not cause any alteration in plant biomass in field soil-grown and EDU-treated plants. Ozone leaf injury, which affected 67% of primary leaf area in non-treated plants, was completely suppressed by EDU doses as low as 100 mg liter −1. This indicates that low concentrations of EDU, which do not affect plant growth in field soil, provide sufficient protection from O 3 injury. The need for careful EDU dose-response studies prior to field assessments is emphasized.

Effect of ethylene diurea (EDU) on ozone tolerance and superoxide dismutase activity in bush bean

The experimental chemical, N-[2-(2-oxo-1-imidazolidinyl)ethyl]- N-phenylurea (Ethylene diurea, EDU) has been reported to protect plants from otherwise injurious doses of the air pollutant, ozone. It has been claimed that EDU provides this protection by causing enhancement of the levels of the oxyradical scavenger, superoxide dismutase (SOD). Studies with Phaseolus vulgaris L. cv Pure Goldwax have confirmed the protective effect of EDU against acute ozone doses which otherwise resulted in visible injury to more than 70% of the area of leaves on untreated plants. However, no significant effects of EDU treatment were observed on SOD levels, in either primary or trifoliate leaves. In this and other cultivars, EDU appears to function via a mechanism which does not involve SOD. Evidence is presented to show that the lack of treatment effects was not the result of possible SOD inactivation during extraction.