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The influence of low SO2 concentrations on growth reduction of Nicotiana tabacum L. cv. samsun and Cucumis sativus L. cv. Unikat
EnvironmentalPollution(SeriesA) 21 (1980)73-76
THE INFLUENCE OF LOW SO 2 CONCENTRATIONS ON GROWTH REDUCTION OF N I C O T I A N A T A B A C U M L. CV. SAMSUN AND C U C U M I S S A T I V U S L. CV. UNIKAT
V. MEJSTI~tK
Environmental Ecology Institute of the Czechoslovak Academy of Sciences, 252 43 Pruhonice, Czechoslovakia
ABSTRACT
The effects offumigation with O.02ppm of SO 2 on Nicotiana tabacum L. cv. Samsun and Cucumis sativus L. cv. Unikitt were investigated for 4 weeks in fumigation chambers. There were significant reductions in the fresh weights of green leaves, shoots and roots, in the root~shoot ratio, the leaf area and all dry weight fractions measured. Greater reductions were found in C. sativus than in N. tabacum. The reduction in the root system fresh weight was 39 % for C. sativus and 83 % for N. tabacum, while leaf area reductions were 5 % and 46 %, respectively. It is concluded that the effects of SO 2 on agricultural crops may be higher than is assumed, with consequent losses in economic yields.
INTRODUCTION
Sulphur dioxide pollution of the environment has been studied more than pollution caused by any other chemical. The most common source of $O2 in the atmosphere is the combustion of fossil fuels and it is well known that susceptible plant species may be damaged by an 8-h exposure to concentrations of 0.05-0-15 ppm SO2 (Guderian & Stratmann, 1968). However, at concentrations below this level the effects of SO 2 are not so easily defined and there is some controversy as to whether adverse effects on plant growth do, in fact, occur. In the experiments conducted by Bell & Clough (1973) it was found that continuous fumigation at both 0.12 and 0-067 ppm SO 2 for 9 and 27 wgeks, respectively, depressed the growth of Lolium perenne L. by approximately 50 %. In contrast, experiments carried out by Cowling et al. (1973) showed that exposure to 0.046 ppm SO 2 for 59 days increased the yield of the same species when it was grown in a sulphur-deficient soil. More recently, Ashenden & Mansfield (1977) have shown that wind speed can influence the sensitivity of plant 73 Environ. Pollut. Ser. A. 0143-1471/80/0021-0073/$02.25 © Applied Science Publishers Ltd, England, 1980 Printed in Great Britain
74
V. MEJSTI~iK
species to $O 2. Ashenden (1978) found that the exposure ofDactylis glomerata L. to 0" 11 ppm SO 2 for four weeks caused a significant reduction in the number of tillers and green leaves, in the leaf area, the root/shoot ratio and dry weight. It was concluded that D. glomerata may be slightly more sensitive to SO 2 than L. perenne. Different plant species and varieties may vary considerably in their sensitivity to SO 2. Susceptibility lists have been compiled by several investigators (O'Gara, 1922; Katz et al., 1939; Barrett & Benedict, 1970; Guderian & van Haut, 1970; D/issler, 1976 and others). These lists should be used only as a guide since variations occur because of differences in geographical location, climate, age of the plant iand the rate of air movement across the leaves. Early investigators (e.g. Stoklasa, 1923), studying the effects of SO 2 on vegetation, concluded that 'invisible injury' could occur in growth or yield of plants, in the absence of chlorotic or necrotic markings. Recent studies in Europe (Guderian, 1977) revealed that reduction in growth and yield occurred without visible marking on certain plants exposed to atmospheric SO 2. This paper describes the effects of low concentrations of SO 2 on the growth and biomass production of Nicotiana tabacum L. cv. Samsun and Cucumis sativus L. cv. Unikfit plants.
MATERIALS AND METHODS
The fumigation system consisted of two chambers (80 x 80 x 100cm), both of which were ventilated with ambient filtered air. The air speed through the chambers was 15 m min- 1. Each chamber was illuminated with sodium lamps providing a light intensity of 81 J m - 2 sec- 1. Plants were illuminated for 12 h and kept in the dark for 12 h. The day temperature was 21-23 °C and the night temperature 18-20 °C. In one chamber SO 2 was released into the air stream from a cylinder at a controlled rate so as to maintain a concentration of 0.02 + 0.005ppm. There was continuous measurement of humidity and SO 2 concentration by means of Novak's coulograph analyser (Novfik, 1965). The relative humidity in both chambers fluctuated between 75 and 87 %. The second chamber was a 'clean air' control and this contained no detectable SO 2. The chambers were described by Mejstfik & Abrah~im (1974). Two separate experiments were carried out. In the first experiment seedlings of Nicotiana tabacum cv. Samsum were used and in the second seedlings of Cucumis sativus cv. Unikfit. Tobacco plants were 4 weeks old at the three-leaf stage and the cucumber plants were 3 weeks old at the three-leaf stage at the beginning of the fumigation experiments. The seedlings were planted in pots containing sandy loam soil (pH 7-2). The plants remained in the chambers for four weeks and during that time were watered daily. Leaf areas were determined by means of a planimeter and then each plant was divided into shoots and roots for fresh and dry weight determinations. The experiments were replicated four times. The data obtained from each experiment were analysed using a paired comparison t-test.
PLANT GROWTH REDUCTION CAUSED BY SO 2
75
RESULTS AND DISCUSSION
In both experiments, SO 2 caused significant reductions in fresh weights of leaves, stems and roots (p < 0-05) and also in the dry weight fractions measured. In the case of tobacco plants leaf area was reduced by only 5.3 % whereas, in the cucumber plants, this reduction was 46.1% (p < 0.05). In both experiments there was a statistically significant reduction in the root/shoot ratio, this being 53.6% for tobacco and 85.8% for cucumber, respectively (p < 0.05). At the end of the experiments there were no necrotic lesions on the leaves of plants exposed to SO 2. The data presented in Tables 1 and 2 clearly demonstrate that an atmosphere polluted with 0.02 ppm of SO 2 for four weeks significantly reduced the growth of tobacco and cucumber plants. The growth reductions were associated in both experiments with a reduction of leaf area but not with a lower number of fully expanded green leaves. The influence of SO2 on the root system appears to be very important. In both our experiments with tobacco and with cucumber plants the dry and fresh weights of the roots were greatly reduced. The observed SO 2 inhibition of root growth could result either directly from SO 2 penetrating the soil or indirectly by SO 2 altering foliar metabolism and reducing the quality and quantity of photosynthate to the roots. The indirect nature of SO 2 inhibition of root growth may have a similar mechanism to that of ozone inhibition (Tingey, 1978). TABLE 1 REDUCTIONS IN PRODUCTIVITY OF Nicotiana tabacum L. cv. SAMSUN PLANTS AFTER BEING GROWN IN 0.02 ppm so 2 COMPARED WITH CLEAN AIR
Root/ shoot ratio
Leaf area (cm 2)
57'065_+13'4 17-376+13'6 74.441_+16.5 !.044±0"3 0-014 69'418_+8"2 26.866±2.5 96-284_+13'1 6.288_+0'4 0'065 17.1 35.3 22-6 83.4 53'5
238-45 251"79 5-3
Leaves Fumigated Control Reduction
(%)
Fresh weights (g) Stems Total shoots
Roots
Dry weights (g) Leaves Roots 5-124 0"!87 6.272 0"513 18"3 82'9
TABLE 2 REDUCTIONSIN PRODUCTIVITYOF Cucumi$ satil)u$ L. CV. UNIKATPLANTSAFTERBEINGGROWNIN 0'02 ppnl SO2 COMPARED WITH CLEAN AIR
Leaves Fumigated Control Reduction
(%)
8"163+1-4 16-855-+1.0 51"5
Fresh weights (g) Stems Total shoots 4-021_+0.8 6.199-+1.2 35"1
12-184+_1,6 23.054-+1,2 47.1
Roots
Root/ shoot ratio
Leaf area (cm 2)
Dry weights (g) Leaves Roots
1.223-+0.8 2.017_+0.2 39.3
0.100 0.706 85"8
32,09 59'56 46.1
0.718 1,079 33.4
0.045 0.104 56.5
76
v. MEJSTi~,JK
It is apparent from the data that C. sativus is slightly more sensitive to SO 2 than N. tabacum under these conditions of exposure. Different plant species vary in their susceptibility to the pollutants and thus no general conclusion may be reached. Nevertheless, these experiments need to be taken into account by practical agronomists who may have regarded these two species as relatively less sensitive to SO2 (Dfissler, 1976). It also raises the question as to whether observations of growth reduction without plant damage after short-term exposure to low SO 2 concentrations of pollutants are valid when predicting the effects of SO 2 in nature. It has been demonstrated (Leone & Brennan, 1970) that plant nutrition can affect the ability of air pollutants to cause visible or invisible damage. In conclusion, we can say that the effects of SO 2 on plants in the field may have been largely under-rated and greater losses in leaf and root production, at least, may be occurring than was previously thought.
REFERENCES ASHENDEN,T. W. (1978). Growth reduction in cocksfoot (Dactylis glomerata L.) as a result of SO 2 pollution. Environ. Pollut., 15, 161-6. ASHENDEN,T. W. & MANSFIELD,T. A. (1977). Influence of wind speed on the sensitivity of ryegrass to SO2. J. exp. Bot., 28, 729-35. BARRETT,T. V. & BENEDICT,H. M. (1970). Sulphur dioxide. In Recognition of air pollution injury to vegetation." A pictorial atlas, ed. by J. C. Jacobson and A. C. Hill, C1-C17. Pittsburg, Pa, Air Pollution Control Association. BELL, J. N. B. & CLOUGH,W. S. (1973). Depression of yield in ryegrass exposed to sulphur dioxide. Nature, Lond., 241, 729-35. COWLING,D. W., JONES,L. H. & LOCKVER,D. R. (1973). Increased yield through correction of sulphur deficiency in ryegrass exposed to sulphur dioxide. Nature, Lond., 243, 479-80. DgSSLEg, H. G. (1976). Einfluss yon Lufiverunreiningungen aufdie Vegetation. Jena, Gustav Fischer Verlag. GUDERIAN,R. (1977). Air pollution. Berlin, Springer Verlag. GUDERIAN,R. & VAN HAUT, H. (1970). Detection of SO2 effects upon plants. Staub, 30, 22-35. GUDERIAN,R. & STRATMANN,H. (1968). Freilandversuche zur Ermittlung yon Schwefeldioxidwirkungen auf die Vegetation, HI Teil. Forschungsberichte des Landes Nordrhein Westfalen No. 1920, K61n und Opladen, Westdt. Verlag. KATZ, M., LEOINGHAM,G. A. & MCCALLUM,A. W. (1939). Symptoms of injury on forest and crop plants. In Effects of sulphur dioxide on vegetation, ed. by M. Katz, Publication No. 815, 51-103. Ottawa, National Research Council of Canada. LEONE, I. A. & BRENNAN,E. (1970). Ozone toxicity in tomato as modified by phosphorus nutrition. Phytopathology, 60, 521-4. Mmsr~ig, V. & ABRAHASt,J. (1974). Komory pro exposici rostlinneho materi~ilu kysli~:nikem sifi6it~,m. Vodni hospodd~stvi--Ochrana ovzduki, 5, 67-9. NOVAK,J. V. A. (1965). Polarographic-coulometric analysers. Measurement of low concentrations of sulphur dioxide. Colin Czech. chem. Commun. Eng. Edn, 30, 2703-16. O'GARA, P. J. (1922). Effects of air pollution on vegetation. In Introduction to the scientific study of atmospheric pollution, ed. by B. M. McCormac, 131-50, Dordrecht, D. Reidel Publishing Co. STOKLASA,J. (1923). Die Beschiidigungen der Vegetation durch Rauchgasse und Fabrikexhalationen. Berlin, Verlag Urban und Schwarzenberg. TINGEY, D. T. (1978). Effects of ozone on root processes. Calif. Environ., 7, 5.
THE INFLUENCE OF LOW SO 2 CONCENTRATIONS ON GROWTH REDUCTION OF N I C O T I A N A T A B A C U M L. CV. SAMSUN AND C U C U M I S S A T I V U S L. CV. UNIKAT
V. MEJSTI~tK
Environmental Ecology Institute of the Czechoslovak Academy of Sciences, 252 43 Pruhonice, Czechoslovakia
ABSTRACT
The effects offumigation with O.02ppm of SO 2 on Nicotiana tabacum L. cv. Samsun and Cucumis sativus L. cv. Unikitt were investigated for 4 weeks in fumigation chambers. There were significant reductions in the fresh weights of green leaves, shoots and roots, in the root~shoot ratio, the leaf area and all dry weight fractions measured. Greater reductions were found in C. sativus than in N. tabacum. The reduction in the root system fresh weight was 39 % for C. sativus and 83 % for N. tabacum, while leaf area reductions were 5 % and 46 %, respectively. It is concluded that the effects of SO 2 on agricultural crops may be higher than is assumed, with consequent losses in economic yields.
INTRODUCTION
Sulphur dioxide pollution of the environment has been studied more than pollution caused by any other chemical. The most common source of $O2 in the atmosphere is the combustion of fossil fuels and it is well known that susceptible plant species may be damaged by an 8-h exposure to concentrations of 0.05-0-15 ppm SO2 (Guderian & Stratmann, 1968). However, at concentrations below this level the effects of SO 2 are not so easily defined and there is some controversy as to whether adverse effects on plant growth do, in fact, occur. In the experiments conducted by Bell & Clough (1973) it was found that continuous fumigation at both 0.12 and 0-067 ppm SO 2 for 9 and 27 wgeks, respectively, depressed the growth of Lolium perenne L. by approximately 50 %. In contrast, experiments carried out by Cowling et al. (1973) showed that exposure to 0.046 ppm SO 2 for 59 days increased the yield of the same species when it was grown in a sulphur-deficient soil. More recently, Ashenden & Mansfield (1977) have shown that wind speed can influence the sensitivity of plant 73 Environ. Pollut. Ser. A. 0143-1471/80/0021-0073/$02.25 © Applied Science Publishers Ltd, England, 1980 Printed in Great Britain
74
V. MEJSTI~iK
species to $O 2. Ashenden (1978) found that the exposure ofDactylis glomerata L. to 0" 11 ppm SO 2 for four weeks caused a significant reduction in the number of tillers and green leaves, in the leaf area, the root/shoot ratio and dry weight. It was concluded that D. glomerata may be slightly more sensitive to SO 2 than L. perenne. Different plant species and varieties may vary considerably in their sensitivity to SO 2. Susceptibility lists have been compiled by several investigators (O'Gara, 1922; Katz et al., 1939; Barrett & Benedict, 1970; Guderian & van Haut, 1970; D/issler, 1976 and others). These lists should be used only as a guide since variations occur because of differences in geographical location, climate, age of the plant iand the rate of air movement across the leaves. Early investigators (e.g. Stoklasa, 1923), studying the effects of SO 2 on vegetation, concluded that 'invisible injury' could occur in growth or yield of plants, in the absence of chlorotic or necrotic markings. Recent studies in Europe (Guderian, 1977) revealed that reduction in growth and yield occurred without visible marking on certain plants exposed to atmospheric SO 2. This paper describes the effects of low concentrations of SO 2 on the growth and biomass production of Nicotiana tabacum L. cv. Samsun and Cucumis sativus L. cv. Unikfit plants.
MATERIALS AND METHODS
The fumigation system consisted of two chambers (80 x 80 x 100cm), both of which were ventilated with ambient filtered air. The air speed through the chambers was 15 m min- 1. Each chamber was illuminated with sodium lamps providing a light intensity of 81 J m - 2 sec- 1. Plants were illuminated for 12 h and kept in the dark for 12 h. The day temperature was 21-23 °C and the night temperature 18-20 °C. In one chamber SO 2 was released into the air stream from a cylinder at a controlled rate so as to maintain a concentration of 0.02 + 0.005ppm. There was continuous measurement of humidity and SO 2 concentration by means of Novak's coulograph analyser (Novfik, 1965). The relative humidity in both chambers fluctuated between 75 and 87 %. The second chamber was a 'clean air' control and this contained no detectable SO 2. The chambers were described by Mejstfik & Abrah~im (1974). Two separate experiments were carried out. In the first experiment seedlings of Nicotiana tabacum cv. Samsum were used and in the second seedlings of Cucumis sativus cv. Unikfit. Tobacco plants were 4 weeks old at the three-leaf stage and the cucumber plants were 3 weeks old at the three-leaf stage at the beginning of the fumigation experiments. The seedlings were planted in pots containing sandy loam soil (pH 7-2). The plants remained in the chambers for four weeks and during that time were watered daily. Leaf areas were determined by means of a planimeter and then each plant was divided into shoots and roots for fresh and dry weight determinations. The experiments were replicated four times. The data obtained from each experiment were analysed using a paired comparison t-test.
PLANT GROWTH REDUCTION CAUSED BY SO 2
75
RESULTS AND DISCUSSION
In both experiments, SO 2 caused significant reductions in fresh weights of leaves, stems and roots (p < 0-05) and also in the dry weight fractions measured. In the case of tobacco plants leaf area was reduced by only 5.3 % whereas, in the cucumber plants, this reduction was 46.1% (p < 0.05). In both experiments there was a statistically significant reduction in the root/shoot ratio, this being 53.6% for tobacco and 85.8% for cucumber, respectively (p < 0.05). At the end of the experiments there were no necrotic lesions on the leaves of plants exposed to SO 2. The data presented in Tables 1 and 2 clearly demonstrate that an atmosphere polluted with 0.02 ppm of SO 2 for four weeks significantly reduced the growth of tobacco and cucumber plants. The growth reductions were associated in both experiments with a reduction of leaf area but not with a lower number of fully expanded green leaves. The influence of SO2 on the root system appears to be very important. In both our experiments with tobacco and with cucumber plants the dry and fresh weights of the roots were greatly reduced. The observed SO 2 inhibition of root growth could result either directly from SO 2 penetrating the soil or indirectly by SO 2 altering foliar metabolism and reducing the quality and quantity of photosynthate to the roots. The indirect nature of SO 2 inhibition of root growth may have a similar mechanism to that of ozone inhibition (Tingey, 1978). TABLE 1 REDUCTIONS IN PRODUCTIVITY OF Nicotiana tabacum L. cv. SAMSUN PLANTS AFTER BEING GROWN IN 0.02 ppm so 2 COMPARED WITH CLEAN AIR
Root/ shoot ratio
Leaf area (cm 2)
57'065_+13'4 17-376+13'6 74.441_+16.5 !.044±0"3 0-014 69'418_+8"2 26.866±2.5 96-284_+13'1 6.288_+0'4 0'065 17.1 35.3 22-6 83.4 53'5
238-45 251"79 5-3
Leaves Fumigated Control Reduction
(%)
Fresh weights (g) Stems Total shoots
Roots
Dry weights (g) Leaves Roots 5-124 0"!87 6.272 0"513 18"3 82'9
TABLE 2 REDUCTIONSIN PRODUCTIVITYOF Cucumi$ satil)u$ L. CV. UNIKATPLANTSAFTERBEINGGROWNIN 0'02 ppnl SO2 COMPARED WITH CLEAN AIR
Leaves Fumigated Control Reduction
(%)
8"163+1-4 16-855-+1.0 51"5
Fresh weights (g) Stems Total shoots 4-021_+0.8 6.199-+1.2 35"1
12-184+_1,6 23.054-+1,2 47.1
Roots
Root/ shoot ratio
Leaf area (cm 2)
Dry weights (g) Leaves Roots
1.223-+0.8 2.017_+0.2 39.3
0.100 0.706 85"8
32,09 59'56 46.1
0.718 1,079 33.4
0.045 0.104 56.5
76
v. MEJSTi~,JK
It is apparent from the data that C. sativus is slightly more sensitive to SO 2 than N. tabacum under these conditions of exposure. Different plant species vary in their susceptibility to the pollutants and thus no general conclusion may be reached. Nevertheless, these experiments need to be taken into account by practical agronomists who may have regarded these two species as relatively less sensitive to SO2 (Dfissler, 1976). It also raises the question as to whether observations of growth reduction without plant damage after short-term exposure to low SO 2 concentrations of pollutants are valid when predicting the effects of SO 2 in nature. It has been demonstrated (Leone & Brennan, 1970) that plant nutrition can affect the ability of air pollutants to cause visible or invisible damage. In conclusion, we can say that the effects of SO 2 on plants in the field may have been largely under-rated and greater losses in leaf and root production, at least, may be occurring than was previously thought.
REFERENCES ASHENDEN,T. W. (1978). Growth reduction in cocksfoot (Dactylis glomerata L.) as a result of SO 2 pollution. Environ. Pollut., 15, 161-6. ASHENDEN,T. W. & MANSFIELD,T. A. (1977). Influence of wind speed on the sensitivity of ryegrass to SO2. J. exp. Bot., 28, 729-35. BARRETT,T. V. & BENEDICT,H. M. (1970). Sulphur dioxide. In Recognition of air pollution injury to vegetation." A pictorial atlas, ed. by J. C. Jacobson and A. C. Hill, C1-C17. Pittsburg, Pa, Air Pollution Control Association. BELL, J. N. B. & CLOUGH,W. S. (1973). Depression of yield in ryegrass exposed to sulphur dioxide. Nature, Lond., 241, 729-35. COWLING,D. W., JONES,L. H. & LOCKVER,D. R. (1973). Increased yield through correction of sulphur deficiency in ryegrass exposed to sulphur dioxide. Nature, Lond., 243, 479-80. DgSSLEg, H. G. (1976). Einfluss yon Lufiverunreiningungen aufdie Vegetation. Jena, Gustav Fischer Verlag. GUDERIAN,R. (1977). Air pollution. Berlin, Springer Verlag. GUDERIAN,R. & VAN HAUT, H. (1970). Detection of SO2 effects upon plants. Staub, 30, 22-35. GUDERIAN,R. & STRATMANN,H. (1968). Freilandversuche zur Ermittlung yon Schwefeldioxidwirkungen auf die Vegetation, HI Teil. Forschungsberichte des Landes Nordrhein Westfalen No. 1920, K61n und Opladen, Westdt. Verlag. KATZ, M., LEOINGHAM,G. A. & MCCALLUM,A. W. (1939). Symptoms of injury on forest and crop plants. In Effects of sulphur dioxide on vegetation, ed. by M. Katz, Publication No. 815, 51-103. Ottawa, National Research Council of Canada. LEONE, I. A. & BRENNAN,E. (1970). Ozone toxicity in tomato as modified by phosphorus nutrition. Phytopathology, 60, 521-4. Mmsr~ig, V. & ABRAHASt,J. (1974). Komory pro exposici rostlinneho materi~ilu kysli~:nikem sifi6it~,m. Vodni hospodd~stvi--Ochrana ovzduki, 5, 67-9. NOVAK,J. V. A. (1965). Polarographic-coulometric analysers. Measurement of low concentrations of sulphur dioxide. Colin Czech. chem. Commun. Eng. Edn, 30, 2703-16. O'GARA, P. J. (1922). Effects of air pollution on vegetation. In Introduction to the scientific study of atmospheric pollution, ed. by B. M. McCormac, 131-50, Dordrecht, D. Reidel Publishing Co. STOKLASA,J. (1923). Die Beschiidigungen der Vegetation durch Rauchgasse und Fabrikexhalationen. Berlin, Verlag Urban und Schwarzenberg. TINGEY, D. T. (1978). Effects of ozone on root processes. Calif. Environ., 7, 5.