NITROGEN OXIDES PRODUCED DURING CO2 ENRICHMENT I. EFFECTS ON DIFFERENT GREENHOUSE PLANTS

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1 New Phytol. (1985) 101, IO3 NITROGEN OXIDES PRODUCED DURING CO2 ENRICHMENT I. EFFECTS ON DIFFERENT GREENHOUSE PLANTS BY LEIV M. Agricultural University of Norway, Department of Floriculture and Greenhouse Crops, P.O. Box 13, N-1432 Aas-NLH (Accepted 10 May 1985) SUMMARY Plants were grown in chambers with COg enrichment (0/il 1"^) and with or without the addition of 0-85 [i\ \~^ nitrogen oxides (NO^). The following species were tested: Lactuca sativa (lettuce), Cucumis sativus (cucumber), Lycopersicon esculentum (tomato), Saintpaulia ionantha, Rosa, Kalanchoe blossfeldiana, Chrysanthemum X motifolium, Helxine soleirolii, Hedera helix, and Nephrolepis exaltata. All species responded positively to an increase in COg level from 330 to 0/*1 \'^. The dry weights of tomato, roses and Saintpaulia responded negatively to the addition of NO^.. In tomato, the reduced dry weight was due to reduction in shoot length and leaf area. In roses the stem was shorter and in Saintpaulia the leaves smaller when NO^ was added. Furthermore, the time to flowering increased and number of flowers/flower buds decreased in Saintpaulia. Key words: Nitrogen oxides, COg enrichment, plant growth. INTRODUCTION It is well established that enriching the greenhouse atmosphere with carbon dioxide stimulates the growth and increases the yield of many crops. Different sources of COg can be used, and burning of hydrocarbons such as kerosene, propane or natural gases is common in many countries. During the burning process t only COg but also nitrogen oxides (NO^) are produced, and concentrations of 0-5 to 1-0/*1 r ^ NO3. have been recorded in greenhouses (Capron & Mansfield, 1975; Hand, 1979; Saxe, 1981; Mortensen, unpublished). The predominant oxide is NO, which is usually present in much higher concentrations than NOg (Capron & Mansfield, 1975; Ashenden, Mansfield & Harrison 1977; Haukeness etal.,\91^; Saxe 1981). Very little information is available regarding the sensitivity of different greenhouse crops to NO^ levels (Hand, 1982). In this paper, the effects of NO^ during CO2 enrichment on 10 different greenhouse crops are reported. M A T E R I A L S AND M E T H O D S Growth chambers Design. Six growth chambers of 6 mm plexiglass were built for the present experiments following the same principles as previously described by Mortensen (1982). Each chamber (685 mm wide, 1090 mm long and 0 mm high) had a volume of 750 litres (Fig. 1). The air was forced by a fan through a channel and a perforated polyethylene plate which functioned as a plant table. The sheet was S03.00/ The New Phytolo.ist

2 IO4 L. M. MORTENSEN Waterflow Airflow Fig. 1. Growth chambers used in the NO^, studies. Ai, air inlet; Ao, air outlet; C, cooling coil; Cm, cooling machine; Ct, contact thermometer; F, fan; Fa, air filter; FI, flowmeter; G, flap valve; H, electric heater; Hy, hygrometer; Irga, infrared gas analyzer; M, mameter; Pa, air pump; Pw, water pump; Rec, recorder; Si, silica-gel; T, thermocouple; W, water bath. perforated with 10 mm holes which made up about 5 % of the total table area (0-61 m^). The air flow measured above the table was 0 2 m s~^ The temperature was controlled by means of a contact thermometer. Heat was supplied by a 700 W electric heater placed in the channel. In order to obtain precise temperature control, refrigerated water was continuously circulated through a copper coil which was placed below the heater in the channel. The air temperature of the chamber was controlled to within ±0-5 C. The number of air exchanges could be controlled within the range 0 to 30 h"^ by a fan and flap valves. Tbe air fiow to the chamber was measured by a calibrated mameter. One fan supplied all six chambers with air through plastic tubes of 45 mm diameter. The COg concentration was controlled by mixing pure COg gas from bottles with fresh air. The COg application rate was controlled by means of capillaries and the concentration was maintained within ± 50 /ul l~^. The COg concentration in the chamber was measured at intervals of 5 min by an infrared gas analyzer (Uras II, Hartman and Braun). An air switch made it possible to analyze six different air streams in sequence. Water vapour was removed by silica-gel and the air was cleaned with a filter before it entered the analyzer. The flow rate was 50 1 h~^ The six growth chambers were placed in a refrigerated room. The light source was fluorescent lamps (Philips T L 33RS) placed above the chambers. The light was measured by means of a Lambda LI-5 B instrument with a quantum sensor (400 to 700 nm). Growth chamber test. Seedlings of Phaseolus vulgaris nanus 'Bon-bon' were potted in 110 mm pots, one seedling per pot. Ten plants were placed in each of the six growthchambers.theplantsweregrownforsixweeksatl8 CandlOO/*mol m"^ s^i photon flux density (24 h d^^). The mean fresh weight per plant varied from 25-1

3 CO2 and growth of plants. I. 105 Table 1. Plants used in NO^ studies, duration of experiments, temperature, and initial dry weight per plant Species Lactuca sativa ' Salina' Cucumis sativus ' Farbiola' Lycopersicon esculentum 'Ida' Saintpaulia ionantha ' Rosa Roccoco' Saintpaulia ionantha ' Lene' Chrysanthemum x morifolium ' Refour' Chrysanthemum x morifolium ' Horim' Rosa 'Mercedes' Kalanchoe blossfeldiana ' Pollux' Helxine soleirolii Hedera helix ' Gloire de Marengo' Hedera helix ' Harald' Nephrolepis exaltata ' Boston' Duration (d) Temperature Dry weight (g) to 28-1 g between the chambers, and these differences were t significant at the P < 0-05 level. Using the six chambers three different treatments were given simultaneously. In the following experiments significant differences were found between plants grown in parallel chambers. All data were subjected to an analysis of variance, and Duncan's multiple range test was used to determine significant differences between treatment means. Experiments with CO^ and Seedlings of Lactuca sativa ' Salina', Cucumis sativus ' Farbiola', Lycopersicon esculentum 'Ida', and young plants of Helxine soleirolii, Hedera helix 'Gloire de Marengo' and 'Harald', Nephrolepis exaltata 'Boston', Kalanchoe blossfeldiana ' Pollux', Saintpaulia ionantha ' Rosa Roccoco' and ' Lena', Chrysanthemum x morifolium ' Refour' and ' Horim', and Rosa ' Mercedes' were used in the experiments. The plants were grown in standard fertilized peat (Floralux) in 110 mm pots. Six plants of each cultivar were placed in each of the six growth chambers. Nutrient solution was given one to three times per week depending on the size of the plants. The photon flux density at the top of the plants was 95 ±5 /imol m"^ s~\ and the photoperiod was 16 h d"^ The water vapour deficit was kept at 500+ Pa. The air temperature was as shown in Table 1. The experimental periods and initial dry weight of the different plants are also given in Table 1. The following treatments were given: (1) 330 /^l T^ COg, (2) 0 /i\ \'^ COg and (3) 0 Jill 1-1 CO JLLI n NO^ {0-70/i\ I'' NO /^l I'' NO^). The number of air changes in the 330 and 0 /il \~^ treated chambers was 30 and 9 h^^ respectively. The desired NO^ concentration was obtained by mixing pure NO gas with the air stream entering the chamber. The flow rate was controlled by a flowmeter with flow-controller. Some of the NO gas reacted with oxygen and thus a concentration of 015/^11"^ NO2 was obtained. The ratio NO/NO2 obtained was similar to that found in greenhouses burning kerosene (Capron & Mansfield, 1975; Ashenden et al., 1977; Haukeness et al. 1978). The NO and NOg concentrations were measured by a Bendix Model 8102 chemi-

4 IO6 L. M. MORTENSEN Table 2. The effect of CO^ and NO^ {0-85 [A T^) on the dry weight (g) per plant CO2 Species Lactuca sativa ' Salina' Cucumis sativus ' Farbiola' Lycopersiocon esculentum 'Ida' Saintpaula ionantha ' Rosa Roccoco' Saintpaulia ionantha ' Lena' Chrysanthemum x morifolium ' Refour' Chrysanthemum x morifolium ' Horim' Rosa 'Mercede' Kalanchoe blossfeldiana Pollux' Helxine soleirolii Hedera helix ' Gloire de Marengo' Hedera helix ' Harald' Nephrolepis exaltata ' Boston' 330/tl 1-1 0/ill-' CO2 l-04b 0-70b 059b 2-99 b 4-03 c M5b 0 79 b l-42a,b 3-79b 2-60 b 438b 4 23 b 3-87b effect CO2 0/ill-' CO^ + NO^ l-81a 1-03 a 079a 4-21 a 638a 1-47 a 1 32a l-70a 4-78 a 365a 6-05 a 5-87a 5-35a 1-81 a 0 94 a 0-56b 3 81a 5-24b 1 36a 1 33a 116b 516a 3-74a 5-44a 5-88a 4-98 a (%) Sensitive tono^ yes yes yes Values within a line followed by different letters are significantly different at the P ^ 0-05 level according to Duncan's multiple range test. luminiscent analyzer for NO and NOg. The minimum detectable concentration was 0-05 /A1 \-\ At termination of the experiments number and area of leaves, plant height, fresh and dry weight, days to flowering, number of fiower buds and number of open flowers were recorded. Because of the long-day treatment Chrysanthemum and Kalanchoe did t fiower, and the cucumber and tomato plants were harvested before fiowering. R E S U L T S AND D I S C U S S I O N All 10 species responded positively to COg enrichment. The increase in dry weight was from 21 to 74% (Table 2). The results support the general findings that CO2 enrichment enhances growth of Cg plants (Kramer, 1981). The results with Saintpaulia, Chrysanthemum, Kalanchoe, Nephrolepis and roses are similar to those previously found in growth room experiments (Mortensen, 1983; Mortensen & Moe, 1983a, 1983b). Only three out of the 10 species responded negatively to application. The tomato seedlings were strongly affected by the 0*85 /A \~^ level. The decrease in dry weight was due to reduced plant height and leaf area (Table 3). Tomato plants have been found to be sensitive to NO^ levels as low as 0-25 fix 1-1 (Taylor & Eaton, 1966; Spierings, 1971; Capron & Mansfield, 1977). Little is kwn about the effects of NO^ on other greenhouse plants (Hand, 1982). In other species, such as beans (Middelton, Darby & Brewer, 1958, Taylor & Eaton, 1966), oats and alfalfa (Hill & Bennett, 1970), and peas (Bull & Mansfield, 1974), a concentration of 0*1 to 0-6 fil \~^ NO^ caused a reduction of photosynthesis. In addition to tomato, roses and Saintpaulia also seem to be sensitive to NO^. In the case of tomato and roses the positive effect of COg enrichment was totally eliminated by NO^.. Saintpaulia * Lena' was less sensitive to NO^, but the growth was significantly reduced. As with tomato the main reason for the negative effect in Saintpaulia was reduced leaf area. In roses NO^ caused a reduced shoot length. In Saintpaulia flowering was affected by COg and NO^. (Table 4). COg enrichment reduced the time till flowering in both cultivars (Mortensen, 1983). NO^. fumigation

5 , CO2 and growth of plants. I. 107 Table 3. The effect of CO^ and NO^ on the growth of tomato Treatment 330/tll-iCO, 0/tll-iCO, looo/tll-i CO, /f 11-1 NO^ Plant height (cm) Number of leaves Total leaf area (cm^) Dry weight (%) Specific leaf weight (mg cm-*) ll-4a,b 7-6 a 8-1 a 359a 401a 5-9 b 6-4 a l-62b l-94a 10-3b 7-6 a 307b 6-5 a 1-80 a Values within a column followed by different letters are significantly different at the P ^ 0-05 level. Table 4. The effect of CO^ and NOy. on flowering of Saintpaulia ionantha ' Rosa Roccoco' {R) and ' Lena' (L) Flowering plants (%) Treatment 330 n\ 1-1 COj 0/tl 1-1 CO2 0/fl 1-1 CO /tl 1-1 NO^ Number of flowers flowerbuds Days to flowering R L R 80a 73b 76a,b L R L 106a 95b looa.b 55c 92a 72 b 13b 77 a 39b Values within a column followed by different letters are significantly different at the P ^ 0-05 level. Strongly delayed the flowering in 'Lena' but less in 'Rosa Roccoco'. The number of flowers + flower buds increased as a result of COg enrichment (Mortensen, 1983), but was signiflcantly reduced by NOac application in both cultivars. No visible injury caused by NO^. was observed in any of the species. ACKNOWLEDGEMENTS The author thanks Mr A. Hamre, Miss M. Siira and Mrs S. Olsen for their technical assistance. This work was performed as part of the project: 'COg and heat from charcoal in greenhouses', supported by a grant from the National Agricultural Research Council and the Royal Ministry of Petroleum and Energy of Norway, REFERENCES A. & HARRISON, K. M. (1977). Generation of air pollutants from kerosene combustion in commercial and domestic glasshouses. Environmental Pollution, ^ BULL, J. N. & MANSFIELD, T. A. (1974). Photosynthesis in leaves exposed to SO^ and NOj. Nature Z50, CAPRON, T. M. & MANSFIELD, T. A. (1975). Generation of nitrogen oxides pollutants during CO, enrichment of glasshouse atmosphere. Journal of Horticultural Science, 50, CAPRON, T. M. & MANSFIELD, T. A. (1977). Inhibition of growth in tomato by air polluted with nitrogen oxides. Journal of Experimental Botany 28, r% ^ o ^, 1 D HAND, D. W (1979). Injury to crops in glasshouse polluted with nitrogen oxides. ADAS Quarterly Review, HAND, D. W. (1982). CO, enrichment, the benefits and problems. Scientific Horticulture 33, HAUKENESS, M. O., MAGINESS, E. A., GREEN, G. H. & BROOKS, E. E. (1978). Using the heat and carbon dioxide from turbine exhaust gases for the production of greenhouse tomatoes. Horticultural Science 31, ASHENDEN, T. W., MANSFIELD, T.

6 io8 L. M. MORTENSEN HILL, A. C. & BENNETT, J. H. (1970). Inbibition of apparent photosynthesis by nitrogen oxides. Atmospheric Environment 4, KRAMER, P. S. (1981). Carbon dioxide concentration, photosynthesis, and dry matter production. BioScience 31, MiDDELTON, J. T., DARBY, E. F. & BREWER, R. F. (1958). Damage to vegetation from polluted atmosphere. Journal of Air Pollution Control Association 8, MORTENSEN, L. M. (1982). Growth responses of some greenhouse plants to environment. III. Design and function of a growth chamber prototype. Scientia Horticulturae 16, MORTENSEN, L. M. (1983). Growth responses of some greenhouse plants to environment. XII. Effect of CO2 on photosynthesis and growth of Saintpaulia ionantha, Kalanchoe blossfeldiana and Nephrolepis exaltata. Meldinger fra Norges Landbrukshogskole 62, MORTENSEN, L. M. & MOE, R. (1983a). Growth responses of some greenhouse plants to environment. VI. Effect of CO2 and artificial light on growth of Chrysanthemum morifolium Ramat. Scientia Horticulturae 19, MORTENSEN, L. M. & MOE, R. (1983b). Growth responses of some greenhouse plants to environment. VII. The effect of CO2 on photosynthesis and growth of roses. Meldinger fra Norges Landbrukshogskole 62, SAXE, H. (1981). NO^. - vaekstreduktion ved CO2 godskning i vaeksthuse..(growth reduction by NO^; during CO2 enrichment in greenhouses, in Danish). Ugeskrift for jordbruk 28, SPIERINGS, F. H. F. G. (1971). Infiuence of fumigations with NO2 on growth and yield of tomato plants. Netherlands Journal of Plant Pathology 77, TAYLOR, O. C. & EATON, F. M. (1966). Suppression of plant growth by nitrogen dioxide. Plant Physiology 41,

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