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The non-specificity of PAN symptoms on tomato foliage
Environmental Pollution (Series A) 32 (1983) 101-108
The Non-Specificity of PAN Symptoms on Tomato Foliage T i m o t h y Lewis & Eileen Brennan Department of Plant Pathology, Rutgers University, The New Jersey Agricultural Experiment Station, New Brunswick, N J, USA
ABSTRACT The so-called classic symptoms of peroxyacetylnitrate phytotoxicity on tomato plants can result from a variety of agents including a mixture of ozone and sulphur dioxide, mites and cold temperatures. Air monitoring data are therefore essential for a positive diagnosis.
INTRODUCTION Although acute ozone toxicity can be readily diagnosed on the basis of symptom expression when a broad spectrum of plant species is examined, a degree of uncertainty arises with the oxidant, peroxyacetylnitrate (PAN), when the appearance of injury symptoms is used as the sole criterion. In the 1940s a characteristic glazing or bronzing of the lower surface of leaves of certain herbaceous crops such as spinach, endive, alfalfa and barley was observed following intense smog episodes in southern California (Middleton et al., 1950; Haagen-Smit et al., 1952). The particular smog component responsible for the damage was later identified as PAN (Stephens et al., 1961). Since that time the appearance of such symptoms on rapidly expanding leaves has been attributed to PAN (Taylor & MacLean, 1970). In 1974 Pearson et al. reported 'PANtype' injury on several tomato cultivars growing in southwestern Ontario, but in the absence of data for PAN concentrations they could not be positive of the diagnosis. Because PAN measurements in ambient air have not been readily available, compared with some of the other air pollutants, great reliance has been placed on symptomatology. Inasmuch 101 Environ. Pollut. Set. A. 0143-1471 /83/$03"00 © Applied Science Publishers Ltd, England, 1983. Printed in Great Britain
102
Timothy Lewis, Eileen Brennan
as we had previously duplicated PAN-like injury on petunia foliage in controlled fumigations with a mixture of ozone and sulphur dioxide (Lewis & Brennan, 1978), we acquired seeds of the tomato cultivars Heinz 1350, Veemore and Ontario 733 from Canada to test them with the pollutant mixture and also to observe their response to ambient air in New Brunswick, NJ. The results of the experiments will be presented in this paper.
MATERIALS A N D METHODS Seeds of the three tomato varieties were germinated in vermiculite and transplanted into 15 cm plastic pots containing a 1:1:1 peat, perlite, soil mixture that had been sterilised and adjusted to pH 6.0. Plants were maintained in a greenhouse supplied with charcoal-filtered air and were fertilised and watered as needed. Plants were grown until flower buds appeared, providing leaves of different physiological ages for pollutant response. At this time plants were either exposed to controlled fumigation or placed outdoors in ambient air. Controlled fumigations were conducted in a dynamic flow-chamber that has been previously described (Leone et al., 1966). Plants were fumigated at 0-1 and 0.2ppm 0 3 or 0.1 and 0.2 ppm SO 2, singly or in combination, for 6 h at 21-24 °C and a relative humidity of 70-75 ~o. Each pollutant level or combination of pollutant levels was repeated four times using three replicates of each variety. After 48 h foliar symptoms were assessed as to type and severity. Plants that had been placed outdoors were observed daily for any symptoms of air pollution injury. Rutgers tomato plants of similar age were maintained for the purpose of comparison, inasmuch as the cultivar is widely used in New Jersey. Oxidants were monitored with a Mast sensor (Mast Development Co., Davenport, Iowa) and PAN was measured by gas chromatography (Lewis, 1981).
RESULTS AND DISCUSSION Observations made on tomato plants following controlled fumigations are presented in Table 1. The lower concentration (0.1 ppm) of 03 caused upper surface bleaching of intermediate-aged leaves (Fig. 1), a typical response of many herbaceous species which was illustrated in Roma VF
Non-specific PAN symptoms on tomato
103
TABLE !
Symptom Developmenton Foliage of Three Tomato Cultivars ExperimentallyExposed to Various Pollutants for 6 h Pollutant
Symptom
Age--leaf affected
Severity
0-! ppm 03
Upper surface bleaching
Intermediate
Moderate
0.2 ppm 03
Bifacial necrosis Upper surface bleaching Interveinal necrosis Bifacial necrosis Uppersurface bleaching Necrosis Bifacialn e c r o s i s Interveinal necrosis Bifacialn e c r o s i s Interveinai necrosis Undersurfaceinterveinal bronzing
Intermediate Youngand old Old Old Intermediate Old Intermediate Old Intermediate Old
Severe Moderate Slight Slight Moderate Moderate Moderate Moderate Severe Severe
Intermediate
Moderate
0.1 ppm SO2 0.2 ppm SO2 0.1 ppm 03 + 0-1 ppm SO2 0.1 ppm 03 + 0.2 ppm SO2 0.2 ppm 03 + 0.1 ppm SO2 0-2 ppm 03 + 0"2 ppm SO2
tomato by Tingey et al. (1973). The higher 0 3 concentration (0.2ppm) induced bifacial necrosis of the intermediate leaves and a bleaching of the young and old leaves. This also is typical of increased O a dosages. Sulphur dioxide symptoms appeared on leaves that were older than those exhibiting O3 symptoms; the lower SO 2 concentration causing interveinal necrosis and the higher concentration, bifacial necrosis, again similar to that observed by Tingey et al. (1973) on Roma VF tomato (Fig. 2). All the pollutant combinations induced a combination of these ozone and sulphur dioxide symptoms with the exception of 0.2 ppm 0 3 and 0.2 ppm SO2. That particular mixture caused a symptom unlike those observed with the individual pollutants. A glazing or bronzing appeared on the undersurface of leaves (Fig. 3); leaves of intermediate age were most severely injured, whereas the young leaves were marked only at the tip and the oldest leaves only at the base. The injury closely resembled the 'PAN-type' injury reported for the three cultivars in southwestern Ontario. Tingey et al. (1973), in their experiments with Roma VF tomato, also reported an undersurface glazing as a result of such mixtures but did not identify the specific O3/SO 2 ratio that caused it. Inasmuch as a picture in their report shows 'upper surface necrotic lesions' and some 'bifacial necrosis' on Roma VF tomato at 0.10ppm 0 3 + 0.25 ppm SO 2 for 4h, the type of symptom response must be dependent on the ratio of the
104
Fig. 1.
Timothy Lewis, Eileen Brennan
Flecking of adaxial leaf surfaces of tomato resulting from an 0 3 exposure of 0-1 ppm for 6 h.
pollutants, as we observed with the three cultivars we tested. In all of our experimental fumigations the order of sensitivity of the cultivars tended to be Ontario > Veemore > Heinz 1350. When the three Canadian and the Rutgers cultivars were grown in pots in ambient air during the summer of 1979, typical ozone bleaching occurred on the upper surface of intermediate-aged leaves of all four cultivars on several occasions. The appearance of symptoms followed episodes when oxidant concentration exceeded 0.06ppm for several hours. Necrotic lesions symptomatic of SO2 were never observed. An undersurface bronzing or glazing of interveinal tissue similar to that observed in the field in Canada was seen on Heinz 1350, Veemore and Ontario 733 between 17 and 19 June, but not on the Rutgers cultivar.
Non-specific P A N symptoms on tomato
Fig. 2.
105
Bifaciai necrosis of tomato leaves resulting from an SO2 exposure of 0.2 ppm for 6h.
There is no evidence, however, that PAN was responsible for the symptom. According to the literature, 15-20pptm PAN for 4h is required to injure tomato plants (Stephens et al., 1961). PAN levels measured in ambient air during the experiment were below the minimum detectability limit, 0.5 pptm, during the 4 days preceding injury and never exceeded 10.3pptm during 1978-1980, so theoretically the PAN level would not have been high enough to injure tomato plants. Unfortunately, air monitoring data for sulphur dioxide were not taken at the New Brunswick site for the few days preceding the appearance of undersurface glazing of tomato leaves, but records for five other New Jersey sites northeast, northwest and south of New Brunswick were available from the Department of Environmental Protection. The hourly maxima for 14 and 15 June at those sites were consistently higher than normal--SO 2 ranged from 0.038 to 0.072ppm and 03 from 0-094 to 0-127ppm. Obviously these concentrations are not as high as the levels used in the controlled fumigations to induce undersurface glazing, but plants have been known to respond to lower concentrations of air pollutants in the field than in greenhouse studies (Lewis & Brennan, 1977). At this time we cannot confirm that a mixture of SO 2 and 0 3 in ambient air injured tomato foliage of the three Canadian cultivars, but it is suspect. The
106
Timothy Lewis, Eileen Brennan
i
o
Fig. 3.
Bronzing of the abaxial leaf surfaces of tomato resulting from a combination of 0.2ppm 03 and 0-2ppm SO2 for 6h.
apparent tolerance of the Rutgers variety should be tested in controlled fumigations. Inasmuch as PAN and a mixture of 03 and SO 2 both produce the same type of symptom on tomato foliage, visual diagnosis must be supported with air monitoring data. One should also be aware that still other agents can produce an undersurface glazing that mimics the symptom produced by air pollutants. During some of our experiments the symptom was observed several times on plants of various tomato cultivars growing in a greenhouse with charcoal-filtered air or in ambient air. Microscopic examination of the foliage revealed the presence of mites
Non-specific PAN symptoms on tomato
107
(Polyphatarsonemus latus Banks), and applications of kelthane (7 g litre- 1) prevented further injury of this type. Inspection of some early literature (Norton, 1910) revealed that low temperature also induces a silvering or glazing o f the undersurface of tomato leaves. These alternative causes of undersurface leaf injury should be ruled out before one considers air pollution to be the causative agent.
ACKNOWLEDGEMENT The research was performed as part of an NJAES Project No. 11150 supported by Hatch Act Funds and the Environmental Protection Agency.
REFERENCES Haagen-Smit, A. J., Darley, E. F., Zaitlin, M., Hull, H. & Noble, W. (1952). Investigation on injury to plants from air pollution in the Los Angeles area. Pl. Physiol., Lancaster, 27, 18-34. Leone, I. A., Brennan, E. & Daines, R. H. (1966). Effect of nitrogen on the response of tobacco to ozone in the atmosphere. J. Air Pollut. Control Ass., 16, 191-6. Lewis, E. & Brennan, E. (1977). A disparity in the ozone response of bean plants grown in a greenhouse, growth chanber or open-top chamber. J. Air Pollut. Control, 27, 889-91. Lewis, E. & Brennan, E. (1978). Ozone and sulfur dioxide mixtures cause a PANtype injury to petunia. Phytopathology, 68, 1011-14. Lewis, T. (1981). Peroxyacetylnitrate (PAN) concentration in the ambient air in New Brunswick, N J, and its relation to other photochemical oxidants and certain meteorological parameters. MS thesis, Rutgers, The State University of New Jersey. Middleton, J. T., Kendrich, J. B., Jr. & Schwalm, H. W. (1950). Injury to herbaceous plants by smog or air pollution. Plant Dis. Rep., 34, 245-52. Norton, J. B. S. (1910). Some unusual tomato variations. Proc. Am. Soc. hort. Sci., 7, 71-5. Pearson, R. G., Drummond, D. B. McIlveen, W. D. & Linzon, S. N. (1974). PAN-type injury to tomato crops in Southwestern Ontario. Plant Dis. Rep., 58, 1105-8. Stephens, E. R., Darley, E. F., Taylor, O. C. & Scott, W. E. (1961). Photochemical reaction products in air pollution. Int. J. Air Water Pollut., 4, 79-100.
108
Timothy Lewis, Eileen Brennan
Taylor, O. C. & Maclean, D. C. (1970). Nitrogen oxides and the Peroxyacetylnitrates. In: Recognition of air pollution injury to vegetation: A pictorialatlas, ed. by J. S. Jacobson and A. Clyde-Hill, El-E14. Pittsburgh, Air Pollution Control Association. Tingey, D. T., Reinert, R. A., Dunning, J. A. & Heck, W. W. (1973). Foliar injury responses of eleven plant species to ozone/sulfur dioxide mixtures. Atmos. Environ., 7, 201-8.
The Non-Specificity of PAN Symptoms on Tomato Foliage T i m o t h y Lewis & Eileen Brennan Department of Plant Pathology, Rutgers University, The New Jersey Agricultural Experiment Station, New Brunswick, N J, USA
ABSTRACT The so-called classic symptoms of peroxyacetylnitrate phytotoxicity on tomato plants can result from a variety of agents including a mixture of ozone and sulphur dioxide, mites and cold temperatures. Air monitoring data are therefore essential for a positive diagnosis.
INTRODUCTION Although acute ozone toxicity can be readily diagnosed on the basis of symptom expression when a broad spectrum of plant species is examined, a degree of uncertainty arises with the oxidant, peroxyacetylnitrate (PAN), when the appearance of injury symptoms is used as the sole criterion. In the 1940s a characteristic glazing or bronzing of the lower surface of leaves of certain herbaceous crops such as spinach, endive, alfalfa and barley was observed following intense smog episodes in southern California (Middleton et al., 1950; Haagen-Smit et al., 1952). The particular smog component responsible for the damage was later identified as PAN (Stephens et al., 1961). Since that time the appearance of such symptoms on rapidly expanding leaves has been attributed to PAN (Taylor & MacLean, 1970). In 1974 Pearson et al. reported 'PANtype' injury on several tomato cultivars growing in southwestern Ontario, but in the absence of data for PAN concentrations they could not be positive of the diagnosis. Because PAN measurements in ambient air have not been readily available, compared with some of the other air pollutants, great reliance has been placed on symptomatology. Inasmuch 101 Environ. Pollut. Set. A. 0143-1471 /83/$03"00 © Applied Science Publishers Ltd, England, 1983. Printed in Great Britain
102
Timothy Lewis, Eileen Brennan
as we had previously duplicated PAN-like injury on petunia foliage in controlled fumigations with a mixture of ozone and sulphur dioxide (Lewis & Brennan, 1978), we acquired seeds of the tomato cultivars Heinz 1350, Veemore and Ontario 733 from Canada to test them with the pollutant mixture and also to observe their response to ambient air in New Brunswick, NJ. The results of the experiments will be presented in this paper.
MATERIALS A N D METHODS Seeds of the three tomato varieties were germinated in vermiculite and transplanted into 15 cm plastic pots containing a 1:1:1 peat, perlite, soil mixture that had been sterilised and adjusted to pH 6.0. Plants were maintained in a greenhouse supplied with charcoal-filtered air and were fertilised and watered as needed. Plants were grown until flower buds appeared, providing leaves of different physiological ages for pollutant response. At this time plants were either exposed to controlled fumigation or placed outdoors in ambient air. Controlled fumigations were conducted in a dynamic flow-chamber that has been previously described (Leone et al., 1966). Plants were fumigated at 0-1 and 0.2ppm 0 3 or 0.1 and 0.2 ppm SO 2, singly or in combination, for 6 h at 21-24 °C and a relative humidity of 70-75 ~o. Each pollutant level or combination of pollutant levels was repeated four times using three replicates of each variety. After 48 h foliar symptoms were assessed as to type and severity. Plants that had been placed outdoors were observed daily for any symptoms of air pollution injury. Rutgers tomato plants of similar age were maintained for the purpose of comparison, inasmuch as the cultivar is widely used in New Jersey. Oxidants were monitored with a Mast sensor (Mast Development Co., Davenport, Iowa) and PAN was measured by gas chromatography (Lewis, 1981).
RESULTS AND DISCUSSION Observations made on tomato plants following controlled fumigations are presented in Table 1. The lower concentration (0.1 ppm) of 03 caused upper surface bleaching of intermediate-aged leaves (Fig. 1), a typical response of many herbaceous species which was illustrated in Roma VF
Non-specific PAN symptoms on tomato
103
TABLE !
Symptom Developmenton Foliage of Three Tomato Cultivars ExperimentallyExposed to Various Pollutants for 6 h Pollutant
Symptom
Age--leaf affected
Severity
0-! ppm 03
Upper surface bleaching
Intermediate
Moderate
0.2 ppm 03
Bifacial necrosis Upper surface bleaching Interveinal necrosis Bifacial necrosis Uppersurface bleaching Necrosis Bifacialn e c r o s i s Interveinal necrosis Bifacialn e c r o s i s Interveinai necrosis Undersurfaceinterveinal bronzing
Intermediate Youngand old Old Old Intermediate Old Intermediate Old Intermediate Old
Severe Moderate Slight Slight Moderate Moderate Moderate Moderate Severe Severe
Intermediate
Moderate
0.1 ppm SO2 0.2 ppm SO2 0.1 ppm 03 + 0-1 ppm SO2 0.1 ppm 03 + 0.2 ppm SO2 0.2 ppm 03 + 0.1 ppm SO2 0-2 ppm 03 + 0"2 ppm SO2
tomato by Tingey et al. (1973). The higher 0 3 concentration (0.2ppm) induced bifacial necrosis of the intermediate leaves and a bleaching of the young and old leaves. This also is typical of increased O a dosages. Sulphur dioxide symptoms appeared on leaves that were older than those exhibiting O3 symptoms; the lower SO 2 concentration causing interveinal necrosis and the higher concentration, bifacial necrosis, again similar to that observed by Tingey et al. (1973) on Roma VF tomato (Fig. 2). All the pollutant combinations induced a combination of these ozone and sulphur dioxide symptoms with the exception of 0.2 ppm 0 3 and 0.2 ppm SO2. That particular mixture caused a symptom unlike those observed with the individual pollutants. A glazing or bronzing appeared on the undersurface of leaves (Fig. 3); leaves of intermediate age were most severely injured, whereas the young leaves were marked only at the tip and the oldest leaves only at the base. The injury closely resembled the 'PAN-type' injury reported for the three cultivars in southwestern Ontario. Tingey et al. (1973), in their experiments with Roma VF tomato, also reported an undersurface glazing as a result of such mixtures but did not identify the specific O3/SO 2 ratio that caused it. Inasmuch as a picture in their report shows 'upper surface necrotic lesions' and some 'bifacial necrosis' on Roma VF tomato at 0.10ppm 0 3 + 0.25 ppm SO 2 for 4h, the type of symptom response must be dependent on the ratio of the
104
Fig. 1.
Timothy Lewis, Eileen Brennan
Flecking of adaxial leaf surfaces of tomato resulting from an 0 3 exposure of 0-1 ppm for 6 h.
pollutants, as we observed with the three cultivars we tested. In all of our experimental fumigations the order of sensitivity of the cultivars tended to be Ontario > Veemore > Heinz 1350. When the three Canadian and the Rutgers cultivars were grown in pots in ambient air during the summer of 1979, typical ozone bleaching occurred on the upper surface of intermediate-aged leaves of all four cultivars on several occasions. The appearance of symptoms followed episodes when oxidant concentration exceeded 0.06ppm for several hours. Necrotic lesions symptomatic of SO2 were never observed. An undersurface bronzing or glazing of interveinal tissue similar to that observed in the field in Canada was seen on Heinz 1350, Veemore and Ontario 733 between 17 and 19 June, but not on the Rutgers cultivar.
Non-specific P A N symptoms on tomato
Fig. 2.
105
Bifaciai necrosis of tomato leaves resulting from an SO2 exposure of 0.2 ppm for 6h.
There is no evidence, however, that PAN was responsible for the symptom. According to the literature, 15-20pptm PAN for 4h is required to injure tomato plants (Stephens et al., 1961). PAN levels measured in ambient air during the experiment were below the minimum detectability limit, 0.5 pptm, during the 4 days preceding injury and never exceeded 10.3pptm during 1978-1980, so theoretically the PAN level would not have been high enough to injure tomato plants. Unfortunately, air monitoring data for sulphur dioxide were not taken at the New Brunswick site for the few days preceding the appearance of undersurface glazing of tomato leaves, but records for five other New Jersey sites northeast, northwest and south of New Brunswick were available from the Department of Environmental Protection. The hourly maxima for 14 and 15 June at those sites were consistently higher than normal--SO 2 ranged from 0.038 to 0.072ppm and 03 from 0-094 to 0-127ppm. Obviously these concentrations are not as high as the levels used in the controlled fumigations to induce undersurface glazing, but plants have been known to respond to lower concentrations of air pollutants in the field than in greenhouse studies (Lewis & Brennan, 1977). At this time we cannot confirm that a mixture of SO 2 and 0 3 in ambient air injured tomato foliage of the three Canadian cultivars, but it is suspect. The
106
Timothy Lewis, Eileen Brennan
i
o
Fig. 3.
Bronzing of the abaxial leaf surfaces of tomato resulting from a combination of 0.2ppm 03 and 0-2ppm SO2 for 6h.
apparent tolerance of the Rutgers variety should be tested in controlled fumigations. Inasmuch as PAN and a mixture of 03 and SO 2 both produce the same type of symptom on tomato foliage, visual diagnosis must be supported with air monitoring data. One should also be aware that still other agents can produce an undersurface glazing that mimics the symptom produced by air pollutants. During some of our experiments the symptom was observed several times on plants of various tomato cultivars growing in a greenhouse with charcoal-filtered air or in ambient air. Microscopic examination of the foliage revealed the presence of mites
Non-specific PAN symptoms on tomato
107
(Polyphatarsonemus latus Banks), and applications of kelthane (7 g litre- 1) prevented further injury of this type. Inspection of some early literature (Norton, 1910) revealed that low temperature also induces a silvering or glazing o f the undersurface of tomato leaves. These alternative causes of undersurface leaf injury should be ruled out before one considers air pollution to be the causative agent.
ACKNOWLEDGEMENT The research was performed as part of an NJAES Project No. 11150 supported by Hatch Act Funds and the Environmental Protection Agency.
REFERENCES Haagen-Smit, A. J., Darley, E. F., Zaitlin, M., Hull, H. & Noble, W. (1952). Investigation on injury to plants from air pollution in the Los Angeles area. Pl. Physiol., Lancaster, 27, 18-34. Leone, I. A., Brennan, E. & Daines, R. H. (1966). Effect of nitrogen on the response of tobacco to ozone in the atmosphere. J. Air Pollut. Control Ass., 16, 191-6. Lewis, E. & Brennan, E. (1977). A disparity in the ozone response of bean plants grown in a greenhouse, growth chanber or open-top chamber. J. Air Pollut. Control, 27, 889-91. Lewis, E. & Brennan, E. (1978). Ozone and sulfur dioxide mixtures cause a PANtype injury to petunia. Phytopathology, 68, 1011-14. Lewis, T. (1981). Peroxyacetylnitrate (PAN) concentration in the ambient air in New Brunswick, N J, and its relation to other photochemical oxidants and certain meteorological parameters. MS thesis, Rutgers, The State University of New Jersey. Middleton, J. T., Kendrich, J. B., Jr. & Schwalm, H. W. (1950). Injury to herbaceous plants by smog or air pollution. Plant Dis. Rep., 34, 245-52. Norton, J. B. S. (1910). Some unusual tomato variations. Proc. Am. Soc. hort. Sci., 7, 71-5. Pearson, R. G., Drummond, D. B. McIlveen, W. D. & Linzon, S. N. (1974). PAN-type injury to tomato crops in Southwestern Ontario. Plant Dis. Rep., 58, 1105-8. Stephens, E. R., Darley, E. F., Taylor, O. C. & Scott, W. E. (1961). Photochemical reaction products in air pollution. Int. J. Air Water Pollut., 4, 79-100.
108
Timothy Lewis, Eileen Brennan
Taylor, O. C. & Maclean, D. C. (1970). Nitrogen oxides and the Peroxyacetylnitrates. In: Recognition of air pollution injury to vegetation: A pictorialatlas, ed. by J. S. Jacobson and A. Clyde-Hill, El-E14. Pittsburgh, Air Pollution Control Association. Tingey, D. T., Reinert, R. A., Dunning, J. A. & Heck, W. W. (1973). Foliar injury responses of eleven plant species to ozone/sulfur dioxide mixtures. Atmos. Environ., 7, 201-8.