EFFECT OF CO 2 ENRICHMENT ON CANOPY PHOTOSYNTHESIS, WATER USE EFFICIENCY AND EARLY DEVELOPMENT OF TOMATO AND PEPPER HYBRIDS

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1 Acta Agronomica Hungarica, 59(3) pp (2011) DOI: /AAgr EFFECT OF CO 2 ENRICHMENT ON CANOPY PHOTOSYNTHESIS, WATER USE EFFICIENCY AND EARLY DEVELOPMENT OF TOMATO AND PEPPER HYBRIDS S. BENCZE 1,I.KERESZTÉNYI 2,B.VARGA 1,B.KÕSZEGI 1,K.BALLA 1, A. GÉMESNÉ-JUHÁSZ 1 and O. VEISZ 1 1 AGRICULTURAL RESEARCH INSTITUTE OF THE HUNGARIAN ACADEMY OF SCIENCES, MARTONVÁSÁR, HUNGARY 2 MOL GROUP, SZÁZHALOMBATTA, HUNGARY Received: 13 January, 2011; accepted: 18 May, 2011 The effect of CO 2 enrichment on the rate of photosynthesis and the water use efficiency (WUE) of young pepper and tomato plants was studied in the phytotron. A CO 2 level of 1000 ppm significantly increased the net assimilation rate in the upper foliage, while the increase was even more considerable in the lower layers of the canopy, with values of up to 100%. The 1500 ppm CO 2 level caused a further substantial increase in CO 2 assimilation and at least doubled (in tomato) or tripled (in pepper) the water use efficiency on a leaf area basis compared to the ambient values. Although the response in terms of photosynthesis and WUE was not variety-specific, there were differences between the pepper hybrids in the biomass components, exceeding 100% for the total biomass at the 1500 ppm CO 2 level. In tomato, however, there was no significant variation in the total biomass of the three hybrids investigated in this early phase of development at either CO 2 level. Key words: elevated CO 2, pepper, tomato, photosynthesis, WUE Introduction As CO 2 is a limiting factor for photosynthesis in C 3 plants, a rise in the atmospheric CO 2 level can be expected to increase the rate of assimilation and enhance dry matter production (Kramer, 1981; Lawlor and Mitchell, 1991). The rate of stimulation is, however, greatly influenced by the growth type and the nutrient supplies (Poorter et al., 1996; Li et al., 2007). The positive effect of CO 2 enrichment is well known and has been applied in horticulture for various species for a long time (Tremblay and Gosselin, 1998; Terbe and Slezák, 2008). CO 2 fertilization can improve fruit yield and composition, and can cause earlier ripening (Wheeler et al., 1997; Csuvár et al., 2009). The early vegetative growth of young plants may be stimulated even more, resulting in heavier transplants, desirable for successful field establishment, without elongation growth (Woodrow et al., /$ Akadémiai Kiadó, Budapest

2 276 S. BENCZE et al. 1987). In tomato transplants, the shoot and root mass and leaf dry weight were demonstrated to increase by 81%, while transpiration decreased by 34% (Woodrow et al., 1987). In a study involving 96 tomato genotypes, young plant growth increased 2.3-fold at the doubled CO 2 level (Lindhaut and Pet, 1990). CO 2 levels higher than ppm, however, are likely to affect plants less favourably (Mortensen, 1987). As atmospheric CO 2 enrichment can be applied successfully in horticulture, the CO 2 emitted by industry could be a possible source for use in plant production. Besides the economic benefits this would also lead to a reduction in total CO 2 emissions and less burdening of the environment. One example in Hungary could be the use of flue gases, originating from the burning of natural gas, for hydrogen production at the Danube Refinery (MOL Group) in Százhalombatta (MOL DSD, 2010; MOL, 2011). As most research on photosynthesis was associated with the light-saturated rate of assimilation, one aim of the present work was to examine how much the actual photosynthetic intensity is stimulated by CO 2 enrichment and to compare responses in different canopy layers. CO 2 concentrations of 1000 and 1500 ppm were examined to reveal differences in the reactions of various pepper and tomato hybrids in terms of photosynthesis, water use efficiency and biomass components. The relationships between photosynthetic parameters and the actual accumulation of biomass components were also investigated in different hybrids at various CO 2 levels to find out if they have a predictive value for the biomass accumulation potential. Preliminary experiment Materials and methods Six-week-old plants of sweet pepper (Capsicum annuum L.) hybrid Kurca RZ F1, and tomato (Lycopersicon esculentum Mill.) hybrid Petula F1 were planted in 3 L pots containing the growth medium E-950 SPEZIAL SUBSTRAT (Stender AG Schermbeck, Germany) and placed in two PGB-96 growth chambers. The distances between the plants were 20 cm for pepper and 35 cm for tomato, while there were approximately 60 cm between the two rows of pots for both the pepper and tomato growth chambers. The plants were irrigated regularly and received nutrients as foliar fertilization (Volldünger Linz) in the 5 th week after planting. The growth conditions were a 16/8 h day-night regime with a temperature of 24/20ºC, while the light intensity was 300 µmol m 2 s 1. The CO 2 level was maintained at either 400 or 1000 ppm (during light hours). Photosynthesis measurements were carried out on four individual plants six weeks after planting using a LiCOR-6400 portable photosynthesis system (Lincoln, Nebraska, USA). Net assimilation rates were recorded at two canopy levels (lower and upper) in pepper and three levels in tomato (low, middle and top) in each CO 2 treatment at a PAR value of 250 m 2 s 1. Measurements on the variation in pepper and tomato hybrids Six-week-old plants of sweet pepper hybrids (Kurca RZ F1 and Hó F1), hot chilli pepper (Darázs F1) and tomato hybrids (Petula F1, Tourance F1 and Flexxion F1) were planted in 10 L pots

3 EFFECT OF CO 2 ENRICHMENT ON TOMATO AND PEPPER 277 containing the growth medium E-950 SPEZIAL SUBSTRAT (Stender AG Schermbeck, Germany). The plants were placed randomly in three PGB-96 growth chambers in which the atmospheric CO 2 levels were 400 (ambient), 1000 and 1500 ppm. The distances between plants and rows were 35 and 60 cm. The temperature was 23/19ºC during the 15/9 h day-night cycle, while the light intensity during growth was µmol m 2 s 1. The plants were irrigated regularly and received 3 dl of 10 g/l Volldünger Linz nutrient solution per pot once a week in the control, and 1.5 times and twice in the case of pepper, and twice and three times a week in the case of tomato at 1000 and 1500 ppm, respectively, starting from the third week after planting. Net assimilation rate (Pn) and transpiration (Tr) were measured at a PAR value of 230 µmol photons m 2 s 1 with a CIRAS-2 portable photosynthesis meter (PP Systems, Amesbury, USA). The water use efficiency (WUE) was calculated as the ratio of Pn (µmol CO 2 m 2 s 1 ) to Tr (mmol H 2 O). Six weeks after planting, two plants from each variety and treatment were analysed for leaf area (LI-3000C Portable Area Meter) and biomass components. Dry weight was determined after 24 h desiccation at 100ºC. Two-way ANOVA (BREEDER software, Láng et al., 2001) was used to compare the effect of CO 2 level and the genotype, while in the preliminary experiment the two factors were the CO 2 level and measurement height for each variety. Correlation analysis was applied on the data set of different CO 2 levels and genotypes to study the relationships between different parameters (Microsoft Excel 2007). Results Effect of CO 2 enrichment on photosynthesis at different canopy levels Substantial increases in the net assimilation rate were recorded for both species in response to the high CO 2 level (Fig. 1). Though the rise in photosynthesis was significant even at the top of the plants, this increase was much more pro- Fig. 1. Effect of CO 2 enrichment on the net assimilation rate of pepper (Kurca) and tomato (Petula) plants 6 weeks after planting at the 400 and 1000 ppm CO 2 levels

4 278 S. BENCZE et al. nounced (up to more than 100%) in the lower layers of the foliage, where the light intensity was poorer. In plants grown at elevated CO 2 (1000 ppm), the rate of photosynthesis in the lowest leaves was nearly as high as in the light-leaves of the control plants. Change in net photosynthesis and water use efficiency in a variety of pepper and tomato hybrids, 6 weeks after planting An additional rise in the CO 2 level resulted in a further increase in photosynthetic activity (Fig. 2). The growth was higher in pepper, where photo- Fig. 2. Effect of CO 2 enrichment on the net assimilation rate in pepper and tomato hybrids

5 EFFECT OF CO 2 ENRICHMENT ON TOMATO AND PEPPER 279 synthesis was 26 40% more intense at 1000 ppm and 71 85% higher at the 1500 ppm CO 2 level. The corresponding increase in tomato was 15 29% and 32 40%, respectively. There were only slight, non-significant differences in the absolute values of photosynthesis between the different hybrids of each species. CO 2 enrichment resulted in very great increases in the water use efficiency, which was % higher in pepper and % higher in tomato at the 1000 ppm CO 2 level. At 1500 ppm it was about three times the control value in pepper and twice or slightly less than three times the control value in tomato (Fig. 3). However, the gain in assimilation compared to the water loss during transpiration was definitely more economical in pepper than in tomato at the highest CO 2 level. Differences between the various hybrids of each species were not distinct in either CO 2 treatment. Fig. 3. Water use efficiency at various CO 2 levels 6 weeks after planting

6 280 S. BENCZE et al. The biomass accumulation till the 6 th week after planting, averaged over the varieties, was greatly enhanced by elevated CO 2, though the extent of change was not significant in all the hybrids (Fig. 4). In pepper, CO 2 enrichment significantly increased the mass of root, stem and leaf, and the leaf area. Darázs had the largest root and stem weights, while Hó had the most leaf area and mass (though not significantly different from Darázs). Kurca had the lowest values for most biomass components. The difference between the hybrids was most extreme at the 1500 ppm CO 2 level, where the total dry biomass of Darázs was double that of Kurca. The extent of increase due to high CO 2 was less pronounced for tomato hybrids and did not reveal significant differences between the hybrids in terms of to- Fig. 4. Effect of CO 2 enrichment on the biomass accumulation of pepper and tomato 6 weeks after planting

7 EFFECT OF CO 2 ENRICHMENT ON TOMATO AND PEPPER 281 tal biomass accumulation. Only the highest CO 2 level resulted in significant rises in the root mass and leaf area of tomato plants, while there was no difference in the stem weights. Leaf mass only increased significantly in Tourance and Flexxion at 1500 ppm CO 2, compared to the ambient values. Though the relative increase in leaf area was less than in pepper, in absolute terms it was considerable, rising by as much as m 2 per plant, resulting in a total leaf area of m 2. The leaf area increase in response to the highest CO 2 level was greater in pepper (50 60%), but the total leaf area was much smaller than in tomato, ranging from m 2 per plant. Relationship between photosynthetic parameters and biomass components The rate of net photosynthesis showed a very close relationship with the total biomass accumulation in both species. The leaf weight and area were also in high positive correlation with Pn, while no significant relationship was found between the root and stem weights and the photosynthetic activity, suggesting that these parameters might be influenced by other factors, such as the genotype effect. A negative correlation was found between transpiration and the biomass components, underlining the phenomenon that plants tend to lose less water at elevated CO 2 levels yet produce higher biomass yields. Besides the leaf and total biomass parameters, the root fresh weight in pepper and the stem fresh weight in tomato exhibited positive correlations with the water use efficiency. Discussion It was suggested previously that it is only worth applying higher CO 2 levels if the light intensity is optimum (Fierro et al., 1993), but it was demonstrated here that in both pepper and tomato photosynthesis is greatly enhanced by high CO 2 level even at low light intensity. The assimilation rate of the lower shade-leaves at high CO 2 was very similar to the values recorded for the upper light-leaves at ambient level. Despite the fact that some authors do not recommend the application of CO 2 concentrations of more than 1000 ppm (Mortensen, 1987), the highest CO 2 concentration investigated (1500 ppm) was found to have the most favourable effect on both species. Photosynthesis was greatly stimulated, water use efficiency improved, and the leaf area and dry matter production increased considerably. There was, however, considerable variation among the pepper hybrids, while the tomato hybrids, which were probably greatly improved varieties, did not show any significant differences in their response to high CO 2. On average, the rise in the root, stem and leaf mass and the total biomass in response to 1000 ppm CO 2 was 44%, 57%, 73% and 51% for pepper and 22%, 20%, 22% and 19% for tomato hybrids, respectively. This is higher than the re-

8 282 S. BENCZE et al. Table 1 Correlation coefficients of the correlation analysis between the photosynthetic and morphological parameters of three hybrids each of pepper and tomato grown at CO 2 levels of 400, 1000 and 1500 pm Pepper Pn Tr WUE Root FW Stem FW Leaf FW Leaf area AGB FW Total biomass FW Root DW Stem DW Leaf DW AGB DW Total biomass DW Tomato Pn Tr WUE Root FW Stem FW Leaf FW Leaf area AGB FW Total biomass FW Root DW Stem DW Leaf DW AGB DW Total biomass DW Numbers in bold represent significant relationships at the p 0.05 probability level. Pn = net photosynthesis (net assimilation rate), Tr = transpiration, WUE = water use efficiency, FW = fresh weight, DW = dry weight, AGB = above-ground biomass ported increases of 4 15% in the roots, 3 10% in the stems, 6 12% in the leaves and 6 10% in the total biomass of tomato plants at various nutrient levels, when exposed to doubled atmospheric CO 2 (Li et al., 2007). In the present study, the 1500 ppm CO 2 concentration stimulated the total biomass accumulation even more; the rise in the total biomass was 90% for pepper and 27% for tomato. The results for tomato were similar to those found by other authors, where CO 2 concentrations of 1050 and 1400 ppm stimulated the dry biomass of tomato plants by 17 and 23%, 66 days after sowing (van Oosten et al., 1995). At 1500 ppm WUE was shown here to increase 2 3-fold in tomato and 3-fold in pepper, which was similar to what was found for tomato plants at twice the ambient CO 2 level (Maggio et al., 2002), for unstressed plants (doubled value) and under severe salt stress (more than three times the value). As the leaf area was also found to increase greatly in the present work, the total canopy water use can be assumed to be higher than that recorded on a leaf area basis (Grodzinski et al., 1986). Enhanced growth and dry matter accumulation were found to be correlated with higher net photosynthetic rates in young vegetative tissues in the case of CO 2 enrichment (Tremblay and Gosselin, 1998). Under the present conditions, not only photosynthesis but also WUE proved to be related to biomass accumulation (negative correlation). The strongest relationships for the net assimilation rate and WUE were found with the total biomass and the leaf parameters. The present results confirmed that very high CO 2 levels can indeed have a large positive effect on the development of both tomato and pepper. Although there was considerable variation among the pepper hybrids, the tomato varieties

9 EFFECT OF CO 2 ENRICHMENT ON TOMATO AND PEPPER 283 were more similar in their reaction to high CO 2. Photosynthesis was greatly stimulated, resulting in a considerable rise in the organic matter production and also in higher leaf area. The water use efficiency on a leaf area basis was greatly improved at 1500 ppm CO 2 concentration, leading to a substantial decrease in the water consumption of the plants. Acknowledgements This research was funded by the Research Innovation Projects No and /2010. References Csuvár, Á., Krecz, Á., Paksi, A., Kassai, T., Dimény, J. (2009): Effect of atmospheric CO 2 enrichment on tomato grown in soil. Cereal Res. Commun., 37, Fierro, A., Tremblay, N., Gosselin, A. (1993): CO 2 enrichment and supplementary lighting improve growth and yield of tomato and pepper transplants. HortScience, 29, Grodzinski, B., Woodrow, L., Leonardos, E. D., Dixon, M., Tsujita, M. J. (1986): Plant responses to short- and long-term exposures to high carbon dioxide levels in closed environments. Adv. Space Res., 18, Kramer, P. J. (1981): Carbon dioxide concentration, photosynthesis, and dry matter production. Bioscience, 31, Láng, L., Kuti, C., Bedõ, Z. (2001): Computerized data management system for cereal breeding. Euphytica, 119, Lawlor, D. W., Mitchell, R. A. C. (1991): The effects of increasing CO 2 on crops photosynthesis and productivity: A review of field studies. Plant Cell Environ., 14, Li, J., Zhou, J-M., Duan, Z-Q., Du, C-W., Wang, H-Y. (2007): Effect of CO 2 enrichment on the growth and nutrient uptake of tomato seedlings. Pedosphere, 17, Lindhaut, P., Pet, G. (1990): Effects of CO 2 enrichment on young plant growth of 96 genotypes of tomato (Lycopersicon esculentum). Euphytica, 51, Maggio, A., Dalton, F. N., Piccini, G. (2002): The effects of elevated CO 2 on static and dynamic indices for tomato salt tolerance. Eur. J. Agron., 16, MOL DSD (2010): Vizsgálati Jegyzõkönyv A Dunai Finomító Hidrogéngyár-2 reformáló kemencéjének emissziós vizsgálatairól. (Determination of emission of the reforming furnace in Hydrogen unit No. 2 of Danube Refinery Test Report). 11 pp. MOL (2011): MOL Group Annual Report 2010 Economic, social and environmental performance. MOL Hungarian Oil and Gas Plc, uploads/file/2010/pdf/en1.pdf; 258 pp. Mortensen, L. M. (1987): Review: CO 2 enrichment in greenhouses. Crop responses. Scientia Hort., 33, Poorter, H., Roumet, C., Campbell, B. D. (1996): Interspecific variation in the growth response of plants to elevated CO 2 : A search for functional types. pp In: Körner, C., Bazzaz, F. A. (eds.), Carbon Dioxide. Populations, and Communities. Academic Press, New York. Terbe, I., Slezák, K. (eds.) (2008): Talaj nélküli zöldséghajtatás. (Vegetable production in soilless cultures.) Mezõgazda Press, Budapest. 372 pp.

10 284 S. BENCZE et al. Tremblay, N., Gosselin, A. (1998): Effect of carbon dioxide enrichment and light. HortTechnology October, 8(4), 5. van Oosten, J. J., Wilkins, D., Besford, R. T. (1995): Acclimation of tomato to different carbon dioxide concentrations. Relationship between biochemistry and gas exchange during leaf development. New Phytol., 130, Wheeler, R. M., Mackowiak, C. L., Stutte, G. W., Yorio, N. C., Berry, W. L. (1997): Effect of elevated carbon dioxide on nutritional quality of tomato. Adv. Space Res., 20, Woodrow, L., Liptay, A., Grodzinski, B. (1987): The effects of CO 2 enrichment and etephon application on the production of tomato transplants. Acta Hort., 201, Corresponding author: Szilvia Bencze Mailing Address: P.O. Box 19 H-2462 Martonvásár, Hungary Fax: benczesz@mail.mgki.hu