Ecological Research Series INTERACTION OF OZONE AND HERBICIDES IN SOYBEANS Environmental Research Laboratory Office of Research and Development U.S. Environmental Protection Agency Corvallis, Oregon 97330 ------- RESEARCH REPORTING SERIES Research reports of the Office of Research and Development, U.S. Environmental Protection Agency, have been grouped into nine series. These nine broad cate- gories were established to facilitate further development and application of en- vironmental technology. Elimination of traditional grouping was consciously planned to foster technology transfer and a maximum interface in related fields. The nine series are: 1. Environmental Health Effects Research 2. Environmental Protection Technology 3. Ecological Research 4. Environmental Monitoring 5. Socioeconomic Environmental Studies 6. Scientific and Technical Assessment Reports (STAR) 7. Interagency Energy-Environment Research and Development 8. "Special" Reports 9. Miscellaneous Reports This report has been assigned to the ECOLOGICAL RESEARCH series. This series describes,research on the effects of pollution on humans, plant and animal spe- cies, and materials. Problems are assessed for their long- and short-term influ- ences. Investigations include formation, transport, and pathway studies to deter- mine the fate of pollutants and their effects. This work provides the technical basis for setting standards to minimize undesirable changes in living organisms in the aquatic, terrestrial, and atmospheric environments. This document is available to the public through the National Technical Informa- tion Service, Springfield, Virginia 22161. ------- EPA-600/3-78-047 May 1978 INTERACTION OF OZONE AND HERBICIDES IN SOYBEANS by Raj Bahadur Mississippi Valley State University Itta Bena, Mississippi 38941 contract no. R-803072 Project Officer David T. Tingey Terrestrial Ecology Branch Corvallis Environmental Research Laboratory Corvallis, Oregon 97330 CORVALLIS ENVIRONMENTAL RESEARCH LABORATORY OFFICE OF RESEARCH AND DEVELOPMENT U.S. ENVIRONMENTAL PROTECTION AGENCY CORVALLIS, OREGON 97330 ------- DISCLAIMER This report has been reviewed by the Corvallis Environmental Research Laboratory, U.S. Environmental Protection Agency, and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the U.S. Environmental Protection Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use. 11 ------- FOREWORD Effective regulatory and enforcement actions by the Environmental Protection Agency would be virtually impossible without sound scientific data on pollu- tants and their impact on environmental stability and human health. Respon- sibility for building this data base has been assigned to EPA's Office of Research and Development and its 15 major field installations, one of which is the Corvallis Environmental Research Laboratory (CERL). The primary mission of the Corvallis Laboratory is research on the effects of environmental pollutants on terrestrial, freshwater, and marine eco- systems; the behavior, effects and control of pollutants in lake systems; and the development of predictive models on the movement of pollutants in the biosphere. This report investigated the possibility of herbicides increasing ozone toxicity. An increased toxicity could significantly affect farming practices. 111 ------- ABSTRACT The purpose of this investigation was to identify potentially damaging herbicide-ozone interactions on soybean so that injury could be reduced by judicious selection of herbicides and tolerant cultivars. The involvement of herbicide influence on stomatal aperture affecting ozone fumigation injury was studied. Soybean cultivars with varying sensitivity to ozone were planted in the greenhouse in soil containing residual levels of atrazine, normally recommend- ed levels of metribuzin or nontreated soil. The herbicide bentazon was also studied, but was applied to foliage when the soybeans were 3 weeks old. After the soybean plants were in the second trifoliolate leaf stage or 3 to 7 days after bentazon treatment they were fumigated with 0, 0.3, or 0.4 ppm ozone. Transpiration rates were monitored to evaluate potential interactions. Atrazine, metribuzin, and bentazon all affected transpiration. The transpiration of the ozone tolerant Hood cultivar was not affected by bentazon alone but after ozone treatment, transpiration increased significantly. The presence of atrazine residues in the soil decreased transpiration after ozone fumigation. In the ozone-susceptible Dare cultivar, bentazon inhibited transpiration, but following ozone fumigation there were significant differ- ences. The cultivar Tracy proved to be very susceptible to metribuzin injury and was intermediate in sensitivity to ozone injury. It responded like Dare to bentazon alone, and like Hood following ozone fumigation. This report was submitted in fulfillment of Contract No. R-803072 by Mississippi Valley State University. Under the sponsorship of the U.S. Environmental Protection Agency. This report covers the period December 1, 1974, to March 31, 1977, and work was completed as of April 30, 1977- IV ------- CONTENTS Page Foreword iii Abstract iv Acknowledgements vi SECTION 1 Introduction 1 SECTION 2 Conclusions 2 SECTION 3 Recommendations 3 SECTION 4 Materials and Methods 4 SECTION 5 Results and Discussion 6 References 18 ------- ACKNOWLEDGMENTS The constant guidance of Dr. David T. Tingey, Plant Physiologist, Terrestrial Ecology Branch of the Corvallis Environmental Research Laboratory Environmental Protection Agency, Corvallis, Oregon is gratefully acknowledged. . I am very sincerely indebted to Dr. Donald Penner, Plant Physiologist and Professor of Crop and Soil Sciences Department, Michigan State University, East Lansing, Michigan for his herbicide sprayer design and data analysis assistance. This investigation could not have been undertaken without the sustained and active support of Dr. Clyde Bishop, Jr., Research and Develop- ment Office of Monitoring & Technical Support, Minority Institutions Research Support Program, U.S. Environmental Protection Agency, Washington, D. C. VI ------- SECTION 1 INTRODUCTION A number of soybean (Glycine max (L.) Merr.) production areas in the midwest and the south are located near large population centers and may experience exposure to ozone pollution. Ozone is the principal toxicant in photochemical smog and the most damaging air pollutant affecting vegetation in the United States (1). Soybeans and navy beans are relatively sensitive to ozone injury and such injury has been reported in the field due to acute ozone exposure because of inversion layers (2). The vast majority of land ( 2,103,625 acres in Mississippi alone) currently in soybean production, especially in the south, is treated with preplant, preemergence, early post-emergence and/or late-directed herbicides. Up to four or five herbicides may be applied because of the long and favorable season for growth of crop and weed plants in the south. Although these herbicides may be selective, subtle effects of certain of these compounds on tolerant crops may occur. This is typified by the effect of atrazine (2- chloro-4-(ethylamino)-6-(isopropylamino)-j3-triazine) on the stomatal closing similar to antitranspirants which have been tested for this use (3). It is believed that ozone enters into the leaves through stomata to cause injury (4). - Thus, compounds affecting transpiration could either increase or antag- onize ozone injury. Conversely, ozone has been shown to alter metabolism rate of the herbicide diphenamid (N,N-dimethyl diphenylacetamide) in plants (5). In the United States over 40,000,000 acres of soybeans are planted annually. Even a slight decrease in yield as a result of ozone damage or an interaction of ozone and herbicides would be manifested in tons of protein which could otherwise be used for human and animal consumption. Numerous research papers have reported the interactions of the factors such as pesticides, temperature, soil moisture, fertilizer types, cultivar differences, and agronomic practices in altering the use of herbicides. An environmental factor which has received only recent attention in relation to cultivar differences and herbicides interactions is ozone (6). The purpose of this proposed research was to study the interactions of herbicides and acute levels of ozone as they might alter the sensitivity of soybean cultivars, Soybean cultivar differences in response to acute ozone dosage were demon- strated by Tingey and et al. (2). Ozone under laboratory conditions has been reported to induce stomatal closure (1). Stomatal closure in ozone treated oats depressed photosynthesis and reduced transpiration. The purpose of this investigation was to: (A) Assess the extent of ozone-herbicide interaction and thus reduce damage to soybeans by selecting herbicides and tolerant cultivars and; (B) Study the behavior and resistance of the stomata as port of entry of ozone and consequent effect on transpiration and growth of soybean plants. ------- SECTION 2 CONCLUSIONS Although ozone enters through the stomata it did not appear to affect transpiration three days after exposure. Thus, measuring transpiration for several days after ozone fumigation is not the most sensitive way of evaluat- ing ozone injury. However, the herbicides bentazon, atrazine, and metribuzin all affected transpiration and in the case of bentazon, subsequent ozone fumigation increased transpiration, indicating a possible bentazon-ozone interaction. The three cultivars studied did not accrue leaf area at exactly the same rate, consequently evaluation of transpiration was more accurate when the rates were based on the pretreatment rate and expressed as a percent- age of that rate. The duration of the experiments was too short to use changes in leaf area as a criteria for either ozone or herbicide injury. Interestingly, the transpiration rate of the three cultivars appeared to be almost identical on a leaf area basis. Thus, the differential sensi- tivity of the three cultivars to ozone does not appear to be related to transpiration differences that could have reflected differences in density of stomatal distribution. ------- SECTION 3 RECOMMENDATIONS The data presented in the report suggest that herbicide-ozone interaction may occur. Measurement of transpiration appears rather insensitive to early evaluation of interaction responses. Thus, future studies should be less difficult to interpret if limited to the study of the bentazon-ozone interact- ion and the use of a more sensitive measurement to detect the interaction response. Studies by Tingey e_t jl. (7) would suggest that measurement of ethylene release would be more sensitive and appropriate to measure the initial response. This should be followed by obtaining fresh weight, dry weight, and plant height data over a time period following fumigation. The basis for the observed action should be pursued. This knowledge could have predictive value in identifying other ozone-related interactions potentially reducing soybean production. ------- SECTION 4 MATERIALS AND METHODS TEST PLANTS Three soybean (Glycine max (L.)Merr.) cultivars primarily grown in the south were selected for this investigation. They were Dare, maturity Group V, selected because of its relative susceptibility to ozone damage (2); Hood, maturity Group VI, selected because of its relative tolerance to ozone damage (2); and Tracy, maturity Group VI, selected because it was relatively toler- ant to herbicide 2,4-DB (8), a recent introduction with very desirable characteristics, but its susceptibility to ozone damage was not known. PLANT GROWTH CONDITIONS Fungicide (spergon) treated seeds of each cultivar, one seed each per 170 g styrofoam cup were planted in 100 oven-dried loamy sand soil that contained 73% sand, 12.5% silt, 14.5% clay and approximately 0.4% organic matter. Each cup of soil was brought to field capacity moisture level by weighing and adding water to each cup immediately after seeding. The plants were randomly placed in a greenhouse with temperatures of 24 4^ 5°C during day and 13 +_ 5°C during night with 75 + 15% relative humidity. The greenhouse lighting was supplemented for 6 hr/day with Sylvania grolux tubes during short days. The light intensity was recorded by Lambda light meter model no. LI-170 and photometric sensor LI-2105. The plants were checked every day for loss of moisture by weighing and watered to field capacity. The plastic lids were placed on the cup around the plants after the seedling had grown to reduce the soil surface water loss by evaporation. The nutrients in the soil maintained satisfactory growth of plants for the duration of the experiments from three to five weeks. The plants were not fertilized to avoid a possible interaction between nutrients and the treatments. ; HERBICIDE TREATMENT AND OZONE FUMIGATION Three herbicides, atrazine (2-chloro-4-(ethylamino)-6-(isopropylamino)- j3-triazine), bentazon (3-isopropyl-lH-2,1,3-benzothiodizin-4(3H)-one 2,2- dioxide), and metribuzin (4-amino-6-tert-butyl-3-(methylthio)-aj3-triazin-5(4H) one) were selected for the interaction study with ozone. Atrazine, reported to decrease stomatal aperture and reduce the transpiration rate, w*as incorpor- ated into the soil mix at 0, .07, .14, .28, .56, or .84 kg/ha to simulate residues that might be present in a soybean-corn rotation. Bentazon, a postemergence herbicide, was applied at 0, 0.56, 0.84 or 1.1 kg./ha when the soybeans were 3 weeks old, had three trifoliate leaves, and a Plastochron Index (P.I.) of 3.5. The P.I. provided a numerical evaluation of leaf age, leaf development, and the physiological maturity of the plant useful for comparing growth stage of plants (Tingey, D.T., 1974 Personal communication). Metribuzin was incorporated into the soil prior to planting at rates of 0, 0.14, 0.28, or 0.56 kg,/ha. Herbicide application rates were determined by adjusting pressure on the nozzle and speed of the conveyor belt carrying the ------- plants under the stationary nozzle. The plants of the three cultivars were exposed to ozone concentrations of 0, 0.3, or 0.4 ppm for 2 hr in chambers previously described (9). Ozone was generated by controlling the flow of dry oxygen through a Sanders' Ozoni- zer with an output of 0.50 mg/hr. The ozone concentration within the chamber was measured with a Mast-ozone meter (model 724-2) interfaced with a recorder, During fumigation the light intensity was 35+5 klux, the temperature was 17 + 2°C, and the relative humidity was 85 + 3% inside and outside the cham- bers in the greenhouse. In the first study, the plants were fumigated 7 days after bentazon application; in the second study, 3 days after bentazon application. TRANSPIRATION RATE MEASUREMENT Changes in transpiration rate were used to assess plant injury due to ozone, the herbicides, or the combination of both. In several studies, rates were also compared to prevailing rates prior to herbicide and ozone treatment. The water loss by plants was determined by weighing each cup every day and adding enough water to the soil so as to bring it up to the original predeter- mined field capacity moisture level. As the plants grew older the predetermined weight of the cup was revised upwards periodically. The leaf surface area was also measured in some experiments with leaf area meter Lambda model no. LI-3000. Transpiration rate and leaf surface area provided the basis for expressing the rate of transpiration in terms of weight/area/time. The plants of the three cultivars were indexed for ozone and herbicide visual injury on a scale ranging from 0 to 100, 4 days after treatment. The injury estimates were made for each trifoliate leaf of the plant and then grouped and averaged for the whole plant. The 0 was for undamaged leaf and 100 for dead leaves. Cultivars Dare and Hood were treated with 1.1 kg/ha bentazon followed with 0.4 ppm ozone fumigation after 3 days and photographed 5 days later for the visual injury scoring. EXPERIMENTAL DESIGN AND DATA ANALYSIS The uniformly selected plants were placed in the greenhouse and in the fumigation chambers according to a randomized complete block design with four to eight replications. The data were statistically analyzed by analysis of variance program by computer at Michigan State University. The significant differences among means of the treatments were determined using Duncan's Multiple Range Test. Herbicide treatments were considered as the main plots, while cultivars and ozone concentrations as the sub-sub plots with a given number of replications in three way factorial experiments. ------- SECTION 5 RESULTS AND DISCUSSION It is generally agreed that ozone enters the plant leaf through the stomata and that oxidant injury occurs first in the vicinity of penetration. In a study to determine whether ozone influenced transpiration in the ozone susceptible Dare cultivar, the tolerant Hood, or Tracy cultivar with or with- out a bentazon treatment 7 days earlier, the results indicated little or no effect of ozone on transpiration (Table 1). Only the Tracy cultivar in the absence of a bentazon treatment showed a slight but significant increase in transpiration. From these results one might speculate that modest levels of ozone pollution do not increase moisture stress on the total plant although the topical or localized effect is severe. In this study the transpiration data are based on the transpiration of the particular plant prior to herbicide or ozone treatment. No differences in transpiration were observed among the three cultivars averaged over all other treatments. The experiment showed that bentazon at 1.1 kg/ha inhibited transpiration when other factors were not considered. This expected result confirmed the previous report of Penner (10) that bentazon rapidly inhibits transpiration. However, the data from this study show two additional interesting features. First, following ozone treatment, the water loss picture is reversed and secondly that the cultivars do not respond similarly. The transpiration of the ozone tolerant Hood was not affected by bentazon alone but after the ozone treatment, transpiration increased significantly. In the susceptible Dare, the bentazon inhibited transpiration, but following ozone fumigation there were no significant differences. Visual injury ratings indicated a bentazon-ozone interaction for Dare but not Hood (Figure 1). Tracy seems to be an intermediate in susceptibility to ozone injury and responded like Dare to bentazon treatment alone and responded like Hood following ozone fumigation. In a repeat experi- ment, bentazon failed to inhibit transpiration in Dare prior to fumigation but did stimulate transpiration again of Tracy at the 0.56 kg/ha rate. The response of Hood in the repeat experiment was similar to that reported in Table 1. In a second study, the application of 0.84 kg/ha of bentazon markedly inhibited transpiration of all three cultivars. This was still evident after ozone fumigation (Table 2). The Tracy cultivar showed less inhibition than Dare or Hood. The Hood cultivar appeared to have significantly lower transpiration than the other two cultivars. In additional experiments with eight replications and application of 0, 0.50, and 1.12 kg/ha of bentazon to the three soybean cultivars the Hood cultivar again had significantly less transpiration than Dare on a per plant basis. However, in this experiment, leaf areas were measured and conversion of transpiration to grams water lost per cm2 per 24 hr showed Dare, Hood, and Tracy to have values of 0.131, 0.138, and 0.131, respectively. Thus the decreased transpiration of Hood cultivar in Tables 2 and 3 is merely a ------- reflection of less leaf area, confirming the results presented in Table 1 indicating no difference among cultivars in transpiration rate. Soybeans frequently follow corn in the crop rotation. It is not unusual for low levels of atrazine to persist into the following year if the weather has been cool and dry during the treatment year. Ladlie _e_t _al_. (H) showed that low levels of atrazine stimulated, whereas higher levels inhibited transpiration. The data obtained in this study (Tables 3 and 4) failed to show the stimulation of transpiration by low rates of atrazine but did show inhibition of transpiration at the 0.84 kg/ha rate. In 1975 low levels of metribuzin acted similarly to atrazine; however, in 1976, 0.28 kg/ha of metribuzin significantly stimulated transpiration (Table 5) . The cultivar Tracy appeared to be much more susceptible to metribuzin injury than the other cultivars. Metribuzin did not appear to interact with ozone fumigation to affect transpiration (Table 6), whereas in another study the presence of 0.14 kg/ha of atrazine in the soil appeared to interact with the ozone fumigation to reduce transpiration (Table 7). These results could have occurred if ozone fumigation initially caused an increase in water loss resulting in increased atrazine uptake. The increased atrazine caused stomatal closure and conse- quent decreased water loss of transpiration. ------- Figure 1. Top left, Dare treated with 1.12 kg/ha bentazon and 0.0 ppm ozone. Visual injury 30-35%. Bottom left, Dare treated with 1.12 kg/ha bentazon and 0.40 ppm ozone. Visual injury 75-80%. Top right, Hood treated with 1.12 kg/ha bentazon and 0.0 ppm ozone. Visual injury 25-30%. Bottom right, Hood treated with 1.12 kg/ha bentazon and 0.40 ppm ozone. Visual injury 35-40%. ------- TABLE 1. THE INFLUENCE OF BENTAZON, CULTIVARS, AND OZONE LEVELS ON TRANSPIRATION OF 3-WEEK-OLD SOYBEAN Bentazon Cultivar Ozone Level Rate (kg/ha) (ppm) Transpiration3 March 6 days after 3 days after o- bentazon treatment zone fumigation (% of base rate) (% of base rate) 0 .56 1.12 0 .56 1.12 0 .56 1.12 0 .56 1.12 0 .56 1.12 Dare Dare Hood Hood Tracy Tracy Dare Dare Hood Hood Tracy Tracy Dare Dare Hood Hood Tracy Tracy Effect of bentazon Effect of bentazon Dare Hood Tracy 0 .4 0 .4 0 .4 0 .4 0 .4 0 .4 0 .4 0 .4 0 ,4 99 cd 90 abed 88 abc 93 abed 92 abed 97 bed 92 abed 90 abed 94 abed 83 a 100 cd 101 d 84 ab 83 a 92 abed 82 a 84 ab 85 ab 139 bed 124 abc 116 ab 138 bed 110 a 142 bed 131 abed 142 bed 138 bed 130 abed 155 d 149 cd 143 bed 136 abed 151 cd 142 bed 150 cd 142 bed averaged over cultivar and ozone levels x varieties 93 b 93 b 85 a averaged over ozone levels 94 be 91 ab 84 a 90 ab 88 ab 87 ab 95 be 101 c 84 a 128 a 141 b 144 b 132 ab 137 abc 139 abc 127 a 134 abc 147 be 126 a 152 c 146 be (continued) ------- Table 1 (continued) Transpirations March Bentazon Cultivar Ozone level 6 days after 3 days after ozone Rate (kg/ha) (ppm) bentazon treatment fumigation (% of base rate) (% of base rate) Effect of ozone averag^ over cultivars and bentazon levels 0 92 a 137 a .4 89 a 138 a Effect of cultivar averaged over all bentazon and ozone levels Dare 90 a 136 a Hood 89 a 136 a Tracy 93 a 141 a Cleans within columns with similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. 10 ------- TABLE 2. THE INFLUENCE OF BENTAZON, CULTIVARS, AND OZONE LEVEL ON WATER LOSS FROM 3-WEEK-OLD SOYBEAN. Bentazon Rate Cultivar (kg/ha) 0 Dare Hood Tracy .84 Dare Hood Tracy Ozone Level (ppm) 0 .4 0 .4 0 .4 0 .4 0 .4 0 .4 Water Loss (3 day average) after ozone fumigation3 (gin/plant) 4.5 d 4.4 cd 4.0 be 3.9 b 4.4 cd 4.8 d 2.4 a 2.7 a 2.7 a 2.5 a 3.6 b 3.6 b Effect of bentazon averaged over cultivars and ozone levels 0 4.3 b ,84 2.9 a Effect of cultivars averaged over bentazon and ozone levels Dare 3.5 b Hood 3.2 a Tracy 4.1 c Effect of bentazon x cultivars averaged over ozone levels 0 .84 0 .84 0 .84 Dare Hood Tracy 4 2 3 2 4 3 .5 d .5 a .9 c .6 a .6 d .6 b LMeans within columns with similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. 11 ------- TABLE 3. THE INFLUENCE OF SIMULATED ATRAZINE RESIDUE LEVELS ON THE TRANSPIRA- TION OF THREE CULTIVARS OF 3-WEEK-OLD SOYBEAN. Atrazine Rate Cultivar Transpiration3 (kg/ha) (gm/plt/24 hr) 0 Dare 8.7 d Hood 8.2 be Tracy 8.5 cd .07 Dare 8.8 d Hood 8.0 ab Tracy 8.7 d ,14 Dare Hood Tracy 8.6 d 7.8 a 8.5 cd Effect of atrazine averaged over all three cultivars 0 8.5 a .07 8.5 a .14 8.5 a Effect of cultivars averaged over all atrazine three levels Dare 8.7 b Hood 8/0 a Tracy 8.5 b cleans within columns with similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. 12 ------- TABLE 4. THE INFLUENCE OF ATRAZINE ON THE TRANSPIRATION AND LEAF AREA OF THREE CULTIVARS OF 3-WEEK-OLD SOYBEAN Transpirational Atrazine Rate Cultivar Water Loss3 Leaf Area (kg/ha) (g/plt/24 hr) (cm2/plt) 0 Dare Hood Tracy .28 Dare Hood Tracy .56 Dare Hood Tracy .84 Dare Hood Tracy 10 10 10 10 9 10 10 10 9 9 9 9 .0 .1 .2 .0 .8 .2 .3 .0 .7 .5 .4 .4 cde cde de cde bed de e cde abc a a a 81 87 83 86 89 85 78 82 69 .1 .2 .2 .6 .9 .4 .4 .4 .0 - - — a a a a a a a a a Effect of atrazlne averaged over all three cultivars 0 10.0 b 83.9 a .28 10.0 b 97.3 a .56 10.0 b 76.6 a .84 9.4 within columns with similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. 13 ------- TABLE 5. THE INFLUENCE OF METRIBUZIN ON TRANSPIRATION AND LEAF AREA OF THREE CULTIVARS OF 3-WEEK-OLD SOYBEAN. Metribuzin Rate Cultivar 0 Dare Hood Tracy .14 Dare Hood Tracy .28 Dare Hood Tracy .56 Dare Hood Tracy Experiment I Transpirationa (g/plt/24 hr) 10.0 cde 10.1 cde 10.0 cde 10.3 de 9.9 cd 10.6 e 10.0 cde 9.6 cd 8.8 b 9.6 cd 9.5 c 7.1 a Experiment II Leaf areaa Transpiration3- (cm2/plt) (g/plt/24 hr) 81.1 ab 87.2 abc 83.2 abc 94.3 c 93.8 c 90.9 be 88.2 be 86.3 abc Dead 82.8 abc 75.6 a Dead 8.7 b 8.2 a 9.6 c 8.4 ab 8.3 ab 8.1 a Effect of metribuzin averaged over all three cultivars 0 10.0 c 8.5 a .14 10.3 c .28 9.5 b 9.0 b .56 8.7 a 8.2 a weans within columns with similar letters are not significantly different at the 5% level by Duncan's Multiple Range Test. 14 ------- TABLE 6. THE INFLUENCE OF METRIBUZIN AND OZONE ON THE TRANSPIRATION OF 3- WEEK-OLD SOYBEAN Metribuzin Rate Cultivar Ozone Level (kg/ha) (ppm) 0 Dare 0 .3 .4 Hood 0 .3 .4 .56 Dare 0 .3 .4 Hood 0 .3 .4 Transpiration3- (% of irate prior to fumigation) 82.4 a 86.1 a 89.3 a 92.1 a 86.7 a 86.4 a 95.3 a 85.1 a 86.3 a 97.0 a 81.1 a 80.9 a i^eans with similar letters are not significantly at the 5% level by Duncan's Multiple Range Test. 15 ------- TABLE 7- THE INFLUENCE OF ATRAZINE AND OZONE ON THE TRANSPIRATION OF 3-WEEK- OLD SOYBEAN Atrazine Rate Cultivar Ozone Level (kg/ha) (ppm) 0 Dare 0 .3 .4 Hood 0 .3 .4 Tracy 0 .3 .4 .14 Dare 0 .3 .4 Hood 0 .3 .4 Tracy 0 .3 .4 Transpiration3 (% of rate prior to fumigation) 82.4 abc 85.1 abc 89.3 abc 92.1 be 86.7 abc 86.4 abc 94.6 be 70.7 a 83.6 abc 91.1 be 92.0 be 80.4 ab 101.9 c 83.6 abc 70.0 a 91.4 be 86.9 abc 78.4 ab Main effect of ozone averaged over cultivars and atrazine rates 0 92.3 b .3 84.2 a .4 81.4 a Main effect of cultivars averaged over ozone and atrazine rates Dare 86.7 a Hood 86.8 a Tracy 84.3 a Main effect of atrazine averaged over ozone and cultivars 0 85.7 a .14 86.2 a (continued) 16 ------- TABLE 7 (continued) Atrazine Rate Cultivar Ozone Level Transpiration3 (kg/ha) (ppm) (% of rate prior to fumigation) Atrazine-ozone interaction 0 0 .3 .4 .14 0 .3 .4 averaged over all cultivars 89. 80. 86. 94. 87. 76. 7 be 9 ab 4 abc 8 c 5 be 3 a Tieans with similar letters are not significantly different by Duncan's Multiple Range Test. 17 ------- REFERENCES 1. Hill, A.C. and L. Littlefield. Ozone. Effect of apparent photosynthesis, rate of transpiration, and stomatal closure in plants. Environ. Sci. Technol. 3:52-56. 1969. 2. Tingey, D.T., R.A. Reinert and H.B. Carter. Soybean Cultivars. Acute foliar response to ozone. Crop Sci. 12:268-270. 1972. 3. Fuehring, H.D. Effect of antitranspirants on field of grain sorghum under limited irrigation. Agron. J. 65:348-351. 1973. 4. Dugger, W.M., Jr., and I.P- Ting. Air pollution oxidants-their effects on metabolic processes in plants. Annual. Rev. Plant. Physiol. 21:215-234. 1970. 5. Hodgeson, R.H. Alteration of diphenamid metabolism by ozone. Weed Sci. Soc. Amer. Abstr. No. 86. 1971. 6. Carney, A.W., G.R. Stephenson, D.P. Ormrod, and G.C. Ashton. Ozone- herbicide interactions in crop plants. Weed Sci. 21:508-511. 1973. 7. Tingey, D.T., C. Standley, and R.W. Field. Stress ethylene evolution: a measure of ozone effects on plants. Atmospheric Environment 10:969-974. 1976. 8. Hartwig, Edgar E. "Tracy1- A New Soybean Variety" MAFES Mississippi Agricultural and Forestry Experiment Station, December, 1973. Information Sheet 1227. 9. Heck, W.W., J.A. Dunning, and H. Johnson. Design for a simple plant exposure chamber. National Center for Air Pollution Control Publica- tion APTD - 68-6. 1968. 10. Penner, D. Bentazon selectivity between soybean and Canada thistle. Weed Res. 15:259-262. 1975. 11. Ladlie, J.S., W.F. Meggitt, and D. Penner. Effect of atrazine on soybean tolerance to metribuzin. Weed Sci. 25:115-121. 1971. 18 ------- TECHNICAL REPORT DATA (Please read Instructions on the reverse before completing) REPORT NO. EPA-600/3-78-047 3. RECIPIENT'S ACCESSI ON1 NO. 4. TITLE AND SUBTITLE Interaction of Ozone and Herbicides in Soybeans 5. REPORT DATE May 1978 6. PERFORMING ORGANIZATION CODE 7. AUTHOR(S) Raj Bahadur 8. PERFORMING ORGANIZATION REPORT NO. 9. PERFORMING ORGANIZATION NAME AND ADDRESS Mississippi Valley State University Itta Bena, Mississippi 38941 10. PROGRAM ELEMENT NO. 1AA602 11. CONTRACT/GRANT NO. R-SC3072 12. SPONSORING AGENCY NAME AND ADDRESS U. S. Environmental Protection Agency Corvallis Environmental Research Laboratory, EBRD, TEB Corvallis, OR 97330 13. TYPE OF REPORT AND PERIOD COVERED Final Dec 1974 to Mar 1977 14. SPONSORING AGENCY CODE EPA/600/02 15. SUPPLEMENTARY NOTES 16'ABSTRACTThe purpose of this investigation was to identify potentially damaging herbi- cide-ozone interactions on soybean so that injury could be reduced by judicious selec- tion of herbicides and tolerant cultivars. The involvement of herbicide influence on stomatal aperture affecting ozone fumigation injury was studied. Soybean cultivars with varying sensitivity to ozone were planted in the greenhous in soil containing residual levels of atrazine, normally recommended levels of metri- buzin or nontreated soil. The herbicide bentazon was also studied, but was applied to foliage when the soybeans were 3 weeks old. After the soybean plants were in the second trifoliolate leaf stage or 3 to 7 days after bentazon treatment they were fumigated with 0, 0.3, or 0.4 ppm ozone. Transpiration rates were monitored to evaluate potential interactions. Atrazine, metribuzin, and bentazon all affected transpiration. The transpiration of the ozone tolerant Hood cultivar was not affected by bentazon alone, but after treatment, transpiration increased significantly. The presence of atrazine residues in the soil decreased transpiration after ozone fumigation. In the ozone-susceptible Dare cultivar, bentazon inhibited transpiration, but following ozone fumigation there were significant differences. The cultivar Tracy proved to be very susceptible to metribuzin injury and was intermediate in sensitivity to ozone injury. It responded like Dare to bentazon alone, and like Hood following ozone fumigation. KEY WORDS AND DOCUMENT ANALYSIS DESCRIPTORS b. IDENTIFIERS/OPEN ENDED TERMS c. COSATI Field/Group ozone herbicides soybeans transpiration atrazine metrabuzin bentazon air pollution terrestrial effects 02/A,D 06/F 13. DISTRIBUTION STATEMENT RELEASE TO PUBLIC 19. SECURITY CLASS (This Report) UNCLASSIFIED 21 . NO. OF PAGES 24 20. SECURITY CLASS (This page) UNCLASSIFIED 22. PRICE EPA Form 2220-1 (9-73) 19 , U.S. GOVERNMENT PRINTING OFFICE, 1978-796-778/142 REGION 10 ------- |