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Ozone, antioxidant spray and meloidogyne hapla effects on tobacco
Abstract
The relationship between ozone and the northern root-knot nematode on tobacco was investigated. Seedlings of tobacco (Nicotiana tabacum L.) cv. Virginia 115 were inoculated and not inoculated with root-knot (Meloidogyne hapla (Chitwood) prior to transplanting to a field plot. One-half the plants were sprayed at weekly intervals with an antioxidant, EDU at the rate of 1 kg ha−1 to protect against oxidant injury. O3 concentrations in excess of 80 ppb were recorded 14 times during the summer of 1982. Ambient ozone inhibited growth and yield of tobacco inoculated and not inoculated with M. hapla. Tobacco inoculated with nematode alone developed significantly more ozone injury than other treatments indicating that tobacco infected with M. hapla is more susceptible to ambient O3. Significantly 20% more galls developed on plants with nematode inoculation compared to plants with nematode inoculation + EDU indicating that EDU indirectly reduced gall development in tobacco. Plants protected with EDU also showed an increase in dry weight of shoot, root and biomass.
... Increase in root weight was significant in both SHM and PEHM S1 (91%), S2 (68%), P1 (69%) and P2 (148%) at vegetative stage while in flowering stage significant increases were recorded as 60%, 31%, 172%, and 67% in S1, S2, P1 and P2, respectively. Bisessar and Palmer (1984) in tobacco and in wheat also reported increase in root weight treated with EDU. Shoot weight was not increased significantly at vegetative stage in both the varieties but significant increases were recorded at flowering stage in 50 ppm of EDU concentration. ...
... Shoot weight was not increased significantly at vegetative stage in both the varieties but significant increases were recorded at flowering stage in 50 ppm of EDU concentration. Increase in shoot weight in tobacco plant treated with EDU was found (Bisessar and Palmer, 1984). ...
... (58%) increases were significant. Positive effects of EDU in various biomass related parameters such as: accumulation of biomass (Singh et al., 2010a, b), allocation of biomass (Kosta-rick and Manning, 1993a, b), root/shoot ratio (Wahid et al., 2012), total biomass (Bisessar and Palmer, 1984) and above-ground biomass (Long and Davis, 1991) have been reported in different crops. Ozone decrease plant biomass by impairing photosynthesis so the allocation of sugar and starch decreases which leads to less biomass . ...
This thesis work pertains to exploring the protective effects of EDU and its impact on two physiologically different crops namely wheat (C3 plant) and maize (C4 plant) against tropospheric ozone pollution. Various parameters including morphophysiological, biochemical and proteomics of wheat and maize have been undertaken under the following chapters of the thesis:
Ozone, its uptake and ozone-induced phytotoxic effects. A brief introduction of EDU and its use as a research tool in many scientific studies have also been mentioned. It’s physical and chemical property has been discussed from different sources. Clearly defined objectives of the thesis have also been given under this section.
Study location, plant materials and methods used for different experiments have mentioned. General characteristic of two crops varieties, fertilization doses used sowing of seeds, their cultivation, sampling in two developmental stages (vegetative and flowering) and harvest stage. Different methods adopted for physiological, biochemical to proteomics and organelle experiments have been described.
Biochemical parameters including chlorophyll content, lipid peroxidation, antioxidant content (ascorbate and glutathione) and antioxidant enzymes viz. superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase have been discussed in relation to EDU treatment in wheat. It is the first report on the effects of EDU on proteins expression patterns in two different varieties and developmental stages for wheat. Differentially abundant leaf proteins concerning their role in EDU protection against ozone phytoxicity have been discussed in detail. Proteins of apoplast and chloroplast have also been discussed under this section.
Two varieties of maize differing in their sensitivity to ozone phytotoxicity have been discussed with relation to various parameters of morpho-physiology (plant growth, physiology, yield), biochemistry (enzyme chemistry) and proteomic studies under two EDU concentration. The biochemical parameter includes pigments, lipid peroxidation, antioxidant content (ascorbate and glutathione) and antioxidant enzymes (superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase). It is also first to report of EDU effects on proteins expression patterns in two maize varieties with two growth stages. Role of proteins in pathways related to C4- Cycle, Calvin cycle and photophosphorylation have also been discussed.
A comparative proteomic study of C3 (wheat) and C4 (maize) crop have been also carried out. Three tables providing common proteins in wheat and maize as well as wheat specific and maize specific has been listed here. Comparative pathway analysis and role of proteins illustrating their functions in both the crops have been discussed. A schematic diagram based on antioxidant and proteome experiments representing the mode of action of EDU is discussed.
Kundan in wheat and SHM 3031 in maize have better growth and yield, their tolerance against ozone stress have been enhanced by EDU treatment. These two varieties also performed better in enzymatic activity in EDU treatment. Total leaf, apoplast and chloroplast proteomics showed that proteins involved in different pathways were also influenced by EDU. Kundan over PBW 343 in wheat and SHM 3031 over PEHM-5 variety in maize have performed better under both the EDU dose and developmental stages. This kind of study can be used to screen ozone sensitive varieties for maximum yield in field grown crops. Ozone tolerant varieties can be recommended to farmers to minimizes the yield losses due to the ozone pollution.
... Moreover, there is a lack of evidence from EDU applications as a soil drench to woody plants, especially on the symbiosis with ectomycorrhizal fungi (ECM). We need to Singh et al. 2010a, 2010bKostka-Rick et al. 1993Wahid et al. 2012Bisessar and Palmer, 1984Long and Davis, 1991Bisessar and Palmer, 1984Bisessar and Palmer, 1984Mersie et al. 1994Astorino et al. 1995Tiwari et al. 2005Pleijel et al. 1999Kostka-Rick et al. 1993 Kostka-Rick and Manning, 1993aElagoz and Manning, 2005Cannon et al. 1993Cannon et al. 1993Tonneijck and van Dijk, 1997Szantoi et al. 2007 Kostka-Rick and Manning, 1993aSingh et al. 2010a, 2010bKostka-Rick and Manning, 1993aHassan et al. 1995Kostka-Rick and Manning, 1993aFumagalli et al. 1997Elliott et al. 1987Hassan et al. 1995Manning et al. 2003Szantoi et al. 2007Kostka-Rick and Manning, 1993a understand whether EDU per se affects ECM and, if it does, how ECM will respond to such effects in long-term. ...
... Moreover, there is a lack of evidence from EDU applications as a soil drench to woody plants, especially on the symbiosis with ectomycorrhizal fungi (ECM). We need to Singh et al. 2010a, 2010bKostka-Rick et al. 1993Wahid et al. 2012Bisessar and Palmer, 1984Long and Davis, 1991Bisessar and Palmer, 1984Bisessar and Palmer, 1984Mersie et al. 1994Astorino et al. 1995Tiwari et al. 2005Pleijel et al. 1999Kostka-Rick et al. 1993 Kostka-Rick and Manning, 1993aElagoz and Manning, 2005Cannon et al. 1993Cannon et al. 1993Tonneijck and van Dijk, 1997Szantoi et al. 2007 Kostka-Rick and Manning, 1993aSingh et al. 2010a, 2010bKostka-Rick and Manning, 1993aHassan et al. 1995Kostka-Rick and Manning, 1993aFumagalli et al. 1997Elliott et al. 1987Hassan et al. 1995Manning et al. 2003Szantoi et al. 2007Kostka-Rick and Manning, 1993a understand whether EDU per se affects ECM and, if it does, how ECM will respond to such effects in long-term. ...
... Moreover, there is a lack of evidence from EDU applications as a soil drench to woody plants, especially on the symbiosis with ectomycorrhizal fungi (ECM). We need to Singh et al. 2010a, 2010bKostka-Rick et al. 1993Wahid et al. 2012Bisessar and Palmer, 1984Long and Davis, 1991Bisessar and Palmer, 1984Bisessar and Palmer, 1984Mersie et al. 1994Astorino et al. 1995Tiwari et al. 2005Pleijel et al. 1999Kostka-Rick et al. 1993 Kostka-Rick and Manning, 1993aElagoz and Manning, 2005Cannon et al. 1993Cannon et al. 1993Tonneijck and van Dijk, 1997Szantoi et al. 2007 Kostka-Rick and Manning, 1993aSingh et al. 2010a, 2010bKostka-Rick and Manning, 1993aHassan et al. 1995Kostka-Rick and Manning, 1993aFumagalli et al. 1997Elliott et al. 1987Hassan et al. 1995Manning et al. 2003Szantoi et al. 2007Kostka-Rick and Manning, 1993a understand whether EDU per se affects ECM and, if it does, how ECM will respond to such effects in long-term. ...
Ground-surface ozone (O3) has been increasing over the last decades, and it is now well known that crop and forestry plants suffer from elevated O3 levels. Ethylene-di-urea (EDU) is considered a chemical that offers protection to the treated plants against Ο3. Increasing evidence on the antiozonate efficacy of EDU against the phytotoxic action of O3 is becoming more readily available. We aimed to review the current literatures on the EDU effects on plants, summarize the findings, note any problems, and formulate conclusions from the existing researches. EDU is a very promising antiozonant with its antiozonate action being observed when applied to roots in the concentrations of 275.7 to 374.3 mg L-1, or on leaves in the concentrations of 365.1 to 519.5 mg L-1. There is an evidence that EDU was more effective in some cultivars compared with others although this remains inexplicable. Additionally, the biochemical mechanism of the antiozonate activity of EDU is not well understood and requires parallel toxicological studies. In summary, EDU must play an important role in O3 research in the future.
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... No significant yield increases of an O 3 -sensitive potato grown in O 3 -free air were recorded. In contrast, increasing application frequency resulted in over-dosing and caused side-effects from EDU treatment on root and shoot biomass (Foster et al. 1983;Bisessar and Palmer 1984). No significant differences in chlorophyll content, foliar injury, plant height, pod number and seed yield of soybean were observed in EDU-treated and untreated plants, when O 3 was absent . ...
... Al-Qurainy (2008) (Ensing et al. 1985;Smith et al. 1987), Asia (Wahid et al. 2001;Agrawal et al. 2004Agrawal et al. , 2005Tiwari et al. 2005;Wang et al. 2007;Singh and Agrawal 2009;Singh et al. 2010b, c), Africa (Hassan et al. 1995;Hassan 2006) and Europe (Ribas and Penuelas 2000;Brunschon-Harti et al. 1995a;Pleijel et al. 1999). Yield increments after the application of EDU onto O 3 exposed plants have been reported for onion (Wukasch and Hofstra 1977), navy bean (Hofstra et al. 1978;Temple and Bisessar 1979;Toivonen et al. 1982), tomato (Legassicke and Ormrod 1981), potato (Bisessar 1982;Clarke et al. 1990;Hassan 2006), tobacco (Bisessar and Palmer 1984), watermelon (Fieldhouse 1978), peanut (Ensing et al. 1985), radish (Kostka-Rick and Manning 1992;Hassan et al. 1995), carrot (Tiwari and Agrawal 2010), bush bean (Kostka-Rick and Manning 1993a, c), snap bean (Vandermeiren et al. 1995), mungbean Singh et al. 2010b), soybean (Wahid et al. 2001), wheat (Agrawal et al. 2004;Tiwari et al. 2005;Wang et al. 2007;Singh and Agrawal 2009) and black gram (Singh et al. 2010c). Applying EDU has increased the number of seeds per plant and total seed weight per plant for two O 3 -sensitive cultivars of soybean, while insignificant effects were observed in the O 3 -tolerant lines for these parameters (Damicone 1985). ...
Rapid economic growth, industrialization, urbanization, and improper implementation of environmental regulations have contributed to increased tropospheric O3 levels since preindustrial times, and this increase has produced a serious air pollution problem. Apart from being a hazardous air pollutant, O3 has also been recognized as the third major (carbon dioxide and methane) green house gas in terms of additional radiative forcing and climate change (Forster et al. 2007). Because of its oxidative capacity, high O3 levels in the atmosphere are detrimental to living organisms, including plants. Ozone is among the most damaging air pollutants to which plants are exposed, and produces substantive plant biomass and yield (seed weight) reductions (Thompson 1992; Agrawal et al. 2005; Manning 2005; Hassan 2006; Hassan and Tewfik 2006; Singh et al. 2009a, 2014; Wahid 2006 a, b; Sarkar and Agrawal 2010a, b; Tripathi and Agrawal 2013). The economic loss for 23 horticultural and agricultural crops from O3 exposure was estimated to be approximately $6.7 billion for the year 2000 in Europe (Holland et al. 2006). Wang and Mauzerall (2004) anticipated economic losses of upto 9 % for four important cereal crops (viz., wheat, rice, maize and soybean) grown in China, South Korea and Japan. To minimize such crop losses many potential antioxidants (e.g., fungicides, insecticides, growth regulators and plant extracts) have been evaluated. Among these, the systemic antioxidant, ethylene diurea, –N-[2-(2-oxo-1-imidazolidinyl) ethyl]-N′ phenylurea (popularly known as EDU) was found to be the most effective.
... A few reports on interactions between air pollutants and plant parasitic nematodes are available but the interactive effects are variable (Weber et al., 1979;Shew et al., 1982;Bisessar and Palmer, 1984; Khan and Khan, 1993). Khan and Khan (1993) reported significantly greater galling and greater egg mass production by the root-knot nematode, Meloidogyne incognita race 1, on tomatoes exposed intermittently to 100 ppb SO2. ...
... Nematode-infected plants developed greater SO2-induced chlorosis and necrosis of leaves than non-infected plants exposed to 100 or 200 ppb SO2. Tobacco plants exposed to 80 ppb ambient 03 developed 20% more galling caused by M. hapla compared to the inoculated plants sprayed with an antioxidant, EDU (ethylenediurea) (N-[2-oxo-l-imidazolidinyl ethyl]-N-phenylurea) (Bisessar and Palmer, 1984). Ozone-injury on leaves also was greater on the nematode infected plants. ...
Infection of plants with root-knot nematode leads to an increase in transpiration rate. We hypothesize that, in infected plants, the diffusive intake of gaseous pollutants would be greater and the interaction between the nematode and pollutant(s) would be governed by the degree of stomatal opening. Tomato plants infected with the root-knot nematode, Meloidogyne incognita were exposed to air containing 0, 50 or 100 ppb of SO2 or O3 for 5 h every third day on 27 occasions in 1988 and 1989. Plants exposed to the gases at 100 ppb had chlorotic and/or necrotic leaves, small shoots and roots, reduced leaf pigment levels and low yield, compared to untreated plants. Greater foliar injury developed on plants exposed to SO2 + O3 mixture. Symptoms were even greater on nematode-infected exposed plants. M. incognita alone reduced tomato yield by 14.4% and induced a 3.6% increase in the width of stomatal pores and a 15.6% increase in the transpiration rate. A positive correlation was observed between stomatal pore width and rate of transpiration. Interaction between SO2 and O3 depended on the presence (significant) or absence (insignificant) of nematodes. Most effects of nematode infection and gas exposures (especially mixtures) were synergistic. Disease intensity (galls per root system) was increased, but nematode reproduction (egg masses per root system, eggs per egg mass) reduced on plants exposed to SO2 and/or O3.
This chapter presents an update of research on the effects of air pollutants on vegetation. It discusses the primary data base for the two pollutants of primary concern to terrestrial ecosystems—ozone and sulfur dioxide. The chapter highlights research areas, discusses the relative importance of other pollutants, and covers some research areas that are receiving little attention at present. It focuses on two areas of critical worldwide interest. It is a synthesis of the understanding of the impact of acidic deposition on terrestrial systems. The chapter discusses the state of the art in regional and national assessment methodology, using an ongoing program as an example. It focuses on ozone and crop production and addresses research with sulfur dioxide and research on forest systems.
Given its high level of phytotoxicity and distribution of elevated concentrations over broad geographic areas, O 3 is considered the most critical air pollutant affecting vegetation in the United States. Diverse experimental methods have been used to assess the impacts of O 3 on the crop yield. Comparisons of plant growth and yield in charcoal-filtered or unfiltered air and the use of chemical protectants show that ambient O 3 levels will reduce the growth and yield of numerous plant species. Ozone studies in open-top field-exposure chambers have provided exposure-response functions needed to evaluate the economic impacts of O 3 on agriculture. Exposure-response functions have been developed for a range of legume, grain, fiber and horticultural crops. Yield reductions (10%) were predicted for several crop species when the 7-hr seasonal mean concentration exceeded 0.04 to 0.05 ppm. for some sensitive cultivars of wheat, kidney bean and soybean, 10 yield reductions occurred at 7-hr mean concentrations of 0.028 to 0.033 ppm. Recent studies, using exposure-response functions developed in open-top chambers, have attempted to assess the national economic consequences of O 3 effects on agriculture. These studies indicate that elevated O 3 concentrations are costing U.S. agricultural producers and consumers between 1.2 and 2.4 billion dollars annually.
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 useful to researchers intended to employ EDU in their research with wild plants, but also to researchers working with air pollution control and other scientists.
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Reviews the effects of O3, SO2, and NO2 on interactions between plants, insects and pathogens, in relation to plant yield effects. -from Authors
Tropospheric ozone (O3) has long been documented to cause an injury to plants, but a plants’ protectant, widely applicable in agronomical practice, does not exist. We evaluated the potential antiozonate efficacy of the antitranspirant di-1-p-menthene (Vapor Gard) compared with ethylenediurea (EDU) on Bel-W3 tobacco plants. Plants were treated either with water, or by EDU (10, 100, and 500 mg dm−3), or by vapor (1, 5, 10, and 50 ml dm−3) and were exposed either to O3-enriched (90 ppb) or O3-free air, for 12 days and 8 h day−1. EDU when applied at 10 mg dm−3 did not protect the plants against O3, but when applied at 100 and 500 mg dm−3 offered a significant protection to the plants. Vapor, when applied at 1 ml dm−3 did not protect the plants against O3, neither by terms of foliar visible injury nor by terms of aboveground biomass. In addition, when applied at 10 and 50 ml dm−3 caused phytotoxicity to all the plants, which it was expressed as necrotic spots on the leaves’ surface, misshaping of the leaves, or short plants' height. It is obvious that vapor does not protect Bel-W3 tobacco plants against O3. The antiozonate role of di-1-p-menthene is species-specific and probably occurs only under short-term exposures.
Study was conducted in the suburbs of Lahore city of Pakistan to ascertain the protective effects of ethylene diurea
(EDU) on three cultivars of sesame plants against ambient air pollutants. Seasonal mean 10 hr pollution levels at the site
remained very high (O3
: 91 ppb; NO2
: 38 ppb; SO2
: 10 ppb). It was found that plants treated with highest EDU
concentration (500 ppm) showed increases in stomatal conductance (52%), transpiration rate (53%) and net photosynthesis
rate (61%) compared with non-EDU treated plants. EDU treated plants depicted luxurious vegetative growth with reduced
rate of leaf senescence compared to control plants. EDU protection was remarkable on different biochemical attributes with
increases recorded in total chlorophyll by 31%, carotenoids by 15%, protein by 62%, and ascorbic acid by 65%. Total dry
biomass was increased from 147-197% and root/shoot ratio from 29-37% in EDU-treated plants compared to plant in nonEDU. Seed yield was greater by 33-43% in different sesame cultivars treated with highest EDU concentration than nonEDU plants demonstrating the efficacy of EDU in preventing air pollutants induced yield losses. The results have wider
implications in understanding the injurious effects of air pollutants on agroeconomic husbandry in Pakistan.
Pollution Pathology has emerged as a distinct discipline which deals with the impact of pollutants on plants and its disease causing agencies. Pollutants have been found to adversely affect not only the plants but also the phytopathogens and above all their pathogenesis. The hitherto scattered information on this aspect has been reviewed in the present write‐up.
The protection of plants against air pollution damage can best be achieved either by developing pollution-tolerant cultivars or by using chemical protectants. Use of chemical protectants such as pesticides, growth regulators, anti-oxidants, fertilizers, etc. is a short-term solution to reduce the risk of air pollution damage. In addition, these protectants help in understanding the mechanism of air pollution toxicity and provide a scientific basis for assessing crop losses in field conditions. 95 refs.
Ethylenediurea (N-[2-(2-xo-1-imidazolidinyl)ethyl]-N′-phenylurea; EDU), is known to protect a wide range of plants against ozone-induced injury. Stem injection of EDU may eventually allow ozone effects on large trees to be assessed in the field. This paper describes an experiment to investigate whether EDU injections can provide protection against ozone episodes over a complete growing season. Young beech (Fagus sylvatica) were exposed during 1989 in semi-open-top chambers to three 2-week episodes of 80 nll−1 ozone for 8 h day−1 or to background concentrations. Immediately before each episode some plants were injected with either EDU solution or water, while others were not injected. The injection technique allowed treatments to be made with little difficulty, and comparison of unijected and water-injected plants showed only minor effects on gas exchange and growth. There were significant effects of ozone and ozone × EDU interactions on gas exchange, but it was not possible to identify a clear protective effect of EDU. Some growth parameters were reduced by ozone exposure both during 1989 (leaf weight) and at harvest in 1990 (root weight, pre-1989 shoot weight, total biomass), but these parameters showed no effect of EDU treatment. Basal diameter growth between October 1989, and June 1990, showed a significant ozone × EDU interaction: high ozone reduced growth of water-injected trees but increased growth of EDU-injected trees. Overall, protection by injection of EDU against the effects of a season of realistic ozone exposure has not yet been demonstrated.
A survey of the recent literature on plant responses to exogenous vitamin application yielded the following results:
Vitamins have been applied by soaking seeds, dipping cuttings, by sprays or dusts and as drenches to soils.
Substantial yield increases due to exogenous vitamin application have been reported by a number of researchers.
Vitamins may cause morphogenetic responses in plants. Most pronounced is the stimulation of root formation and of flowering under non‐inductive conditions.
Certain vitamins protect plants against ozone and sulfur dioxide, two important agents of air pollution.
The establishment of appropriate standards to protect vegetation requires an understanding of the bridge between ambient air quality exposure and ultimate response. This paper discusses the ambient air quality-vegetation response system and suggests various approaches that could be used to identify an appropriate and simple O3 standard which could provide the needed degree of environmental protection. Repeated peak O3 concentrations appear to be responsible for affecting vegetation. Plants are sensitive to different hourly mean O3 distribution patterns, even though the seasonal mean may be the same. The application at all locations of a long-term O3 standard will not protect vegetation from repeated peaks. In establishing a secondary O3 standard, more effort should be made to develop a short-term O3 standard that accommodates repeated exposure of vegetation to peak concentrations. Vegetation effects data derived from experiments applying ambient O3 exposures or regimes that mimic ambient conditions should be used as the primary data set to identify the hourly O3 distribution patterns that elicit adverse vegetation responses.
Intermittent exposure of tomato plants (cv. Pusa Ruby) to SO(2) at 286 microg m(-3) (3 h every heavy third day for 75 days) induced slight chlorosis of leaves. At 571 microg m(-3), considerable chlorosis with browning developed on the foliage. These symptoms were more pronounced and appeared earlier on SO(2)-exposed plants infected with Meloidogyne incognita race 1 (Mi), especially in post- and concomitant-inoculation exposures. Mi and/or SO(2) significantly reduced different parameters of plant growth. Synergistic (positive) interactions between SO(2) and Mi occurred in concomitant- and post-inoculation exposures at 286 and 571 microg m(-3), respectively. In other treatments, an antagonistic (negative) interaction was observed. However, in a few cases, additive effects of SO(2) and Mi were also recorded. Intensity of root-knot (galling) was enhanced at both concentrations of SO(2), while reproduction (egg mass production) of Mi was enhanced in concomitant-inoculation exposures at 286 microg m(-3) and inhibited at 571 micro m(-3). Exposure to SO(2) and/or Mi decreased the number and size of stomata but increased the number and length of trichomes on both the leaf surfaces. Stomatal aperture was significantly wider in the plants exposed to 571 microg SO(2) m(-3) alone and in pre-, post-, and concomitant-inoculation exposures at 286 or 571 microg m(-3). Stomatal aperture was directly related to foliar injury and reductions in growth, yield, and leaf pigments.
Although terrestrial vegetation has been exposed to UV-B radiation and ozone over the course of evolutionary history, it is essential to view the effects on vegetation of changing levels of these factors in the context of other features of climate change, such as increasing CO(2) levels and changes in temperature and precipitation patterns. Much of our understanding of the impacts of increased UV-B and ozone levels has come from studies of the effects of each individual factor. While such information may be relevant to a wider understanding of the roles that these factors may play in climate change, experience has shown that the interactions of environmental stresses on vegetation are rarely predictable. A further limitation on the applicability of such information results from the methodologies used for exposing plants to either factor. Much of our information comes from growth chamber, greenhouse or field studies using experimental protocols that made little or no provision for the stochastic nature of the changes in UV-B and ozone levels at the earth's surface, and hence excluded the roles of repair mechanisms. As a result, our knowledge of dose-response relationships under true field conditions is both limited and fragmentary, given the wide range of sensitivities among species and cultivars. Adverse effects of increased levels of either factor on vegetation are qualitatively well established, but the quantitative relationships are far from clear. In both cases, sensitivity varies with stage of plant development. At the population and community levels, differential responses of species to either factor has been shown to result in changes in competitiveness and community structure. At the mechanistic level, ozone generally inhibits photosynthetic gas exchange under both controlled and field conditions, and although UV-B is also inhibitory in some species under controlled conditions, others appear to be indifferent, particularly in the field. Both factors affect metabolism; a common response is increased secondary metabolism leading to the accumulation of phenolic compounds that, in the case of UV-B, offer the leaf cell some protection from radiation. Virtually no information is available about the effects of simultaneous or sequential exposures. Since both increased surface UV-B and ozone exposures have spatial and temporal components, it is important to evaluate the different scenarios that may occur, bearing in mind that elevated daytime ozone levels will attenuate the UV-B reaching the surface to some extent. The experimentation needed to acquire unequivocal effects data that are relevant to field situations must therefore be carried out using technologies and protocols that focus on quantification of the interactions of UV-B and ozone themselves and their interactions with other environmental factors.
Greenhouse and ambient air experiments have shown ethylene diurea (EDU) to be a strong and specific protective suppressant of ozone injury in plants. To examine how EDU affects plant responses to various ozone (O(3)) levels under controlled field conditions, Phaseolus vulgaris L. cv. Lit was treated with 150 ppm EDU every 14 days and exposed in open-top chambers to charcoal-filtered air (CF), nonfiltered air (NF) or two cf treatments with ozone added. The ozone treatments were proportional additions of one (CF1) and two (CF2) times ambient ozone levels. The mean ozone concentrations in the CF, NF, CF1 and CF2 treatments were 0.98, 14.1, 14.98 and 31.56 nl litre(-1). A two-way split plot ANOVA revealed that shoot dry weight was significantly reduced by ozone. EDU treatment was highly significant for leaf dry weight, root dry weight and shoot dry weight, but not for pod dry weight; leading to a higher biomass of EDU-treated plants. Ozone/EDU interactions were significant for root weight only, indicating that EDU reduced growth suppression by ozone. These results show that EDU action on plant biomass could be interpreted as a delay in senescence since EDU-treated plants showed a significant decreased biomass loss even in the CF treatment.
The single and combined effects of ozone (O(3)) and Fusarium oxysporum on growth and disease expression of soybean genotypes differing in foliar sensitivity to O(3) were studied in the greenhouse. O(3) had no effect on root and hypocotyl rot severity of PI 153.283 (O(3)-sensitive, S) or PI 189.907 (O(3)-tolerant, T) maturity group I soybean lines. Plants of both genotypes infected with F. oxysporum and exposed to O(3) had greater reductions in relative growth rate (RGR), net assimilation rate (NAR), and had more stippled leaves per plant than Fusarium-free plants exposed to O(3). O(3) alone had a greater impact on shoot dry weight, RGR, and NAR of PI 153.283 (S) than of PI 189.907 (T). O(3) alone reduced shoot and root dry weights primarily through a depression in NAR and less through reduced leaf area. F. oxysporum alone reduced root dry weight at 35 days; however, infected plants responded with increases in root dry weight from 49 to 63 days. Similarly, F. oxysporum alone lowered early RGR but subsequent RGR decline was less rapid while NAR remained high, particularly during later sampling intervals. Infection by F. oxysporum that causes root and hypocotyl rot increased soybean sensitivity to O(3) by prolonging active vegetative growth.
Three rates of ethylenediurea were used to assess the impact of ambient ozone on growth and productivity of wheat (Triticum aestivum L) cultivars "Malviya 533" (M 533) and "Malviya 234" (M 234) at a suburban site near Varanasi, India, beginning in December. Wheat plants were treated with EDU at 0, 150, 300 and 450 ppm as soil drenches at 10-day intervals. EDU treatment affected plant growth, with effects varying with cultivar, age, and EDU concentration. Seed yield was improved for M 533 at 150 ppm EDU, while yield improved for M 234 at 300 and 450 ppm EDU. M 533 appears to be more resistant to ozone than M 234. Overall results confirmed that EDU is very useful in assessing the effect of ambient ozone in India.
Potato ( Solanum tuberosum L. cv Norchip) plants were exposed under field conditions to ambient ozone and natural infection of early blight incited by Alternaria solani (Ell. & G. Martin) Jones & Grout. Oxone concentrations in excess of 8.0 pphm were recorded on 18 days during the summer of 1979. Foliar ozone symptoms first occurred during flowering; 3 weeks later early blight infection occurred. Ozone and blight injuries were reduced with 10- and 7-day interval foliage sprays using an antioxidant, ethylene diurea (EDU), and a fungicide, chlorthalonil (Bravo), respectively. Plants protected by either EDU or chlorthalonil exhibited significantly less ozone injury and blight injury than nonsprayed control potatoes, with EDU having the greater effect. Fungicide-antioxidant combination sprays were even more effective in reducing both early blight infection and ozone injury. The fungus colonized ozone-injured sites more than non-ozone-injured areas of the foliage, suggesting that ozone injury was a factor in increased infection of potato leaves by A. solani. Increases observed in potato tuber weights paralleled the decreases observed in ozone and blight foliar injury. The combined effects of fungicide and antioxidant were additive in reducing ozone injury and in increasing tuber weight.
A suspected interaction between ozone injury and Botrytis spp. infection on onions (Allium cepa L.) was investigated in the field by reducing one or both causal agents by chemical antioxidants and/or fungicides. Autumn Spice and Rocket onions received 4 sprays of the fungicide anilazine and/or one of the following chemicals with antioxidant properties: fenarimol, ancymidol, chlormequat, piperonyl butoxide, metiram, chlorthalonil, or DuPont DPX-4891. Ozone levels exceeded 4 hourly averages of 8 pphm on at least 7 occasions during July, ozone injury was routinely observed in the field, and Botrytis was frequently isolated from lesions on onion leaves. Single and combination treatments of all fungicides and antioxidants generally reduced leaf necrosis and the Botrytis incident. Fungicide-antioxidant combination treatments were superior to either fungicide or antioxidants alone in reducing Botrytis infection. Yields of Autumn Spice were increased by most treatments while Rocket onion yields were generally decreased. DPX-4891, the only antioxidant which was nonfungitoxic to Botrytis in vitro, was frequently superior to fungicides in preventing botrytis lesions and was also the most effective in reducing ozone injury. These results support the hypothesis that onions injured by ozone are more susceptible to Botrytis infection. 16 references, 5 tables.
The effects of air pollution on the reproduction of five species of plant-parasitic nematodes with different feeding habits and host effects were studied by exposing soybean or begonia hosts to ozone (O3) and sulfur dioxide (SO2), singly or in combination, and to charcoal filtered (control) air. Exposure of infected soybean plants to O3 and O3-SO2 mixture inhibited reproduction and development of Heterodera glycines and Paratrichodorus (Nanidorus) minor, but the increase of Belonolaimus longi caudatus was usually unaffected. Exposure of soybean host plants to SO2 enhanced the reproduction of Pratylenchus penetrans compared with that in plants exposed to the charcoal filtered air control or to O3. Foliar injury of begonia by O3 or an O3-SO2 mixture inhibited the increase of Aphelenchoides fragariae. The suppressive effects of A. fragariae were greater in leaves pre-exposed to O3 or an O3-SO2 mixture before rather than after leaves were inoculated with nematodes. The growth of nematode infested soybean plants and leaves of begonia was inhibited by O3 and the O3-SO2 mixture compared with that of similar control plants grown in the presence of nematodes and charcoal filtered air. Nodulation of soybean plants inoculated with B. longicaudatus and P. minor was suppressed by O3 and the O3-SO2 mixture. The inhibition of nodulation of soybean by H. glycines was extensive; the pollutants had no further detectable effect.
Influxes of polluted air and attacks of tobacco weather fleck in southwestern Ontario were accurately forecast from the synoptic weather pattern and from considerations of mesoscale meteorological systems. However, the principal air pollutant, ozone, occurred daily at low concentrations that were often not followed by corresponding amounts of damage. This difficulty was largely removed by modification of the dose term with the coefficient of evaporation. The latter may empirically represent physiological and physical factors affecting gas exchange. A related downward flux of ozone might be important in determining the amount of ozone available for absorption. The threshold doses of air-polluting ozone and experimentally generated ozone were approximately the same.
Tomato plants (Lycopersicon esculentum 'Walter') were inoculated with initial population densities of Pratylenchus penetrans ranging 0-4000 nematodes per pot and were repeatedly exposed to ozone (Oâ). Exposures to charcoal-filtered air served as controls. Decreases in dry weights of plant parts excised from tomato plants exposed to 0.2 ..mu..l Oâ per liter of air added to the decrease in dry weight caused by exposure to sulfur dioxide (SOâ) at 0.2 ..mu..l/L of air adequately predicted the decrease in dry weight of tomato plants caused by exposure to 0.2 ..mu..l Oâ + 0.2 ..mu..l SOâ per liter of air. When 0.2 ..mu..l Oâ and 0.8 ..mu..l SOâ per liter of air were present in mixture, they acted antagonistically and caused less change in leaf and shoot dry weight than could be predicted by the main effects of Oâ or SOâ. The presence of P. penetrans attacking the roots enhanced the negative effects of Oâ + SOâ on leaf growth (dry weight), but suppressed the inhibitory effects of Oâ + SOâ on auxillary shoot dry weight. Treatments containing 0.8 ..mu..l SOâ per liter of air reduced tomato fruit weight, but the amount of reduction was antagonized by the presence of Oâ.
An interaction between ozone and bacterial blight incited by Xanthomonas phaseoli on white beans (Phaseolus vulgaris 'Sanilac') was investigated in the field by reducing ozone injury with the antioxidant EDU (N-2-(2-oxo-1-imidazolidinyl)ethyl-N-phenylurea). Plants were inoculated with X. phaseoli at time of flowering and weekly sprays of EDU at 1 kg/ha were begun at the same time. Potentially phytotoxic concentration of ozone in excess of 8 pphm were recorded 11 times during the summer of 1977. Infection with X. phaseoli reduced symptoms of foliar ozone injury 19% on plants not treated with antioxidant but X, phaseoli did not protect against ozone injury on treated plants. Ozone injury did not protect against blight infection. Plants protected with EDU averaged 38% less ozone injury and became defoliated 3 wk later than control plants. Yields of EDU-protected plants increased 24% relative to unprotected controls. Weight of bean seeds was inversely correlated with per cent leaflet abscission, suggesting that increases in yield of EDU-protected white bean plants may have been due primarily to reduced defoliation rather than to reduce foliar injury.
Selected materials were sprayed on field-grown plants to control weather fleck. Treated and untreated plants were compared for effectiveness in preventing this physiological disorder and for effects on the leaves. Five of 32 test materials, namely diphenylamine, phenothiazine, 1,4-naphthoquinone, dichlone and N,N′-diphenyl-p-phenylenediamine, were effective in preventing weather fleck. Diphenylamine, phenothiazine, and 1,4-naphthoquinone were particularly effectve. Small amounts of leaf damage occurred on plants sprayed with these three materials, but such damage was insufficient to cause quality depreciation of the cured leaves. No leaf damage occurred on spraying with dichlone and N,N′-diphenyl-p-phenylenediamine, but excessive green fixation, which reduces leaf value, occurred in leaves from dichlone-sprayed plots. Phenothiazine caused some green fixation.
Effects of ontogeny, genome, nitrogen, and water supplies and ozone itself in predisposing tobacco plants to ozone damage (including weather fleck) are described from experiments in both field and greenhouse. The fully expanded leaf became susceptible to low doses of ozone at the time its protein content started to fall. Topping slowed the development of susceptibility of leaves, with the result that the susceptibility of the plants was decreased. Effects of genome were at least partly of an ontogenetic nature. Susceptibility was enhanced by both deficiency and excess of nitrogen. Moisture prior to fumigation increased susceptibility. Long term effects of moisture supply were akin to its influence on drought-hardiness. Susceptibility was increased by shortened photoperiod, low day temperature, and high night temperature, indicating a protective influence of photosynthat. A large or a small dose of ozone appeared to predispose against or toward, respectively; susceptibility to the next dose. Wherever tested, stomatal opening was positively associated with damage. Since stomatal opening regulates the flux of ozone into the leaf, it controls the amount of damage to tissue of a given degree of susceptibility.
Fourteen day old Pinto beans (Phaseolus vulgaris L.) were fumigated continuously from 1 to 5 days with .05 ppm ozone. The unifoliate leaves after 3 days of fumigation exhibited premature senescence. This effect was not increased by longer fumigation. Lateral buds in the axils of the unifoliate leaves were stimulated to elongate, whereas the leaves were reduced in size and weight. Avena coleoptile straight growth tests were made to test the possible relation of the presence of auxin-like material to the premature leaf senescence and bud elongation. Although definite auxin-like activity was observed, the data did not suggest a mechanism for premature senescence of the unifoliate leaves or the elongation of buds.
The antioxidant N-(2-(2-oxo-1-imidazolidinyl)ethyl)-N'-phenylurea (EDU) was compared with carboxin and benomyl, two fungicides with antioxidant properties, for effectiveness in suppressing ozone injury on navy beans (Phaseolus vulgaris). EDU was most effective in reducing bronzing and delaying leaf drop, and increased yield by up to 36%. Part of the yield increase was due to larger seed size. The effectiveness was affected by timing of applications of the antioxidant, the amount of bronzing on the crop, and the sensitivity of the cultivar to ozone. 8 references, 2 tables.
The apparatus for the Oostenbrink direct cottonwool filter extraction method was modified for more efficient use of laboratory space. Yields of Pratylenchus penetrans were larger than those of Xiphinema americanum by this method but the converse was true for the Cobb method.
Chronic exposure of Pinto bean plants to levels of ozone sufficient to cause foliar injury adversely affected shoot and root growth and vigour and enhanced senescence. These effects were reflected in quantitative rather than qualitative differences in the successional root surface fungi. More fungal colonies were consistently isolated from the roots and hypocotyls of plants exposed to ozone than from those grown in charcoal-filtered air. Roots and hypocotyls of plants exposed and not exposed to ozone were colonised by the same fungi and each had the same general mycoflora at each sampling period. Rhizobium nodules were found on the roots of plants grown in charcoal-filtered air, but were not found on the roots of plants grown in the ozone chamber.
Ozone and Borrytis spp. 1982. Ontario Ministry of Agr. and Food. Publ. 298. interaction in onion leaf dieback: field studies
- R T Wukasch
- G Hofstra
Anonymous (1982) Tobacco production recommendations Wukasch R. T. and Hofstra G. (1977) Ozone and Borrytis spp. 1982. Ontario Ministry of Agr. and Food. Publ. 298. interaction in onion leaf dieback: field studies. J. Am. Ser. Bisessar S. (l982) Effects of ozone, antioxidant protection, Horl. Sci. 102, 543-lF16.
Reduced ozone injury on virus-infected tobacco in the field
- Bisessar