Atmospheric CO2 enrichment and plant dry matter content

Agricultural and Forest Meteorology, 43 (1988) 171-181

171

Elsevier Science Publishers B.V., Amsterdam-- Printed in The Netherlands

ATMOSPHERIC C02 ENRICHMENT AND PLANT DRY MATTER CONTENT S.B. IDSO and B.A. KIMBALL U.S. Water Conservation Laboratory, 4331 E. Broadway, Phoenix, AZ 85040 (U.S.A.)

J.R. MAUNEY Western Cotton Research Laboratory, 4335 E. Broadway, Phoenix, AZ 85040 (U.S.A.)

(Received October 18, 1987; revision accepted December 31, 1987)

ABSTRACT

Idso, S.B., Kimball, B.A. and Mauney, J.R., 1988. Atmospheric C02 enrichment and plant dry matter content. Agric. For. Meteorol.43: 171-181. Fresh and dry plant weightswere measuredthroughout a number of different C02 enrichment experiments with six terrestrial plants and two aquatic species. Similar data were also extracted from the literature for 18 additional plants. In general, C02 enrichment had little effect on plant percentagedry matter content, exceptunder conditionsconduciveto starch accumulationin leaves, and then it caused an increase in percentage dry matter content.

INTRODUCTION Increasing the carbon dioxide (CO2) content of the atmosphere generally increases the rates at which plants grow and the harvestable yields they ultimately produce. In a survey of literally hundreds of such observations, for instance, Kimball (1983a,b) found t h a t a 300/lmol C02 mol-1 air increase in atmospheric CO2 concentration increased the average yield of all plants tested by ~ 30%. A question t h a t has rarely been considered in this regard, however, has to do with the effects of atmospheric CO2 enrichment on percentage plant dry matter content, i.e., the percentage of the total fresh weight of the plant t h a t is composed of dry matter. Is it increased, decreased or unaffected by increasing the CO2 content of the air? T h a t this question is not insignificant is demonstrated by the fact t h a t Lemon (1977, 1983 ) has twice suggested in major research reviews t h a t atmospheric C02 enrichment may merely put more water into the treated plants with no concomitant increase in dry m a t t e r content. In an example (attributed to C.T. de Wit) of lettuce grown commercially in CO2-enriched glasshouses in Holland, he has even gone so far as to state t h a t "the canny D u t c h m e n are selling more water to the housewives - - water packaged in green leaves!"

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© 1988 Elsevier Science Publishers B.V.

172

In the yield data analyzed by Kimball, however, many of the reported observations were of grain production, where dry matter accounts for the bulk of the kernel weight; and these observations tend to contradict the spirit of Lemon's contention. Hence, in an attempt to shed more light on the topic, we decided to obtain matching sets of fresh and dry weights as a matter of standard pro. cedure in the course of our many experiments on the effects of elevated CO, concentrations on plant growth and development; and in the following pages we report the results of the work we have completed to date. We also report fresh and dry weight data we have extracted from several prior report.s of CO~ enrichment by other investigators. MATERIALS AND METHODS

The plants we have studied and for which we present original data in this paper are: carrot (Daucus carota I.. var. sativus cv. Red Cored Chantenay }, cotton ( Gossypiurn hirsutum L. Deltapine-61 ), radish ( Raphanus sativa L. cv. Cherry Belle ), soybean ( GIycine max (L.) Merr. cv. Bragg), water fern (AzoUa pinnata var. pinnata), water hyacinth (Eichhornia crassipes (Mart.) Solms ~. the leaf succulent Agave vilmoriniana Berger, and tomato (Lycopersicon esculentum Mill. cv. Tropic ). Primary reports on physiological responses of all of these plants to atmospheric CO2 enrichment have previously been published. Specifically, S,G. Alien et al. (1988a,b) describe our work with water fern, Idso et al. (1985, 1986a) report on two of our experiments with water hyacinth, Idso et al. ( 1987a ) and Kimball et al. (1985, 1986) detail various aspects of our several cotton studies, while Idso et al. ( 1987b ) deals with all of the plants but soybean (which has been even more intensively studied by Acock et al. (1985), L.H. Allen et al. (1987, 1988) and Jones et al. (1984, 1985), from whom we obtained seed for our experiments), Agave vilmoriniana Berger was studied by Idso et al. (1986b), and tomato was studied by Kimball and Mitchell (1979). All of the original data utilized in this report were obtained at Phoenix, Arizona over the period 1977-1987. The greater portion of the data came from plants grown out-of-doors in identical ambient (340/~mol CO2 mol- 1 air) and CO2-enriched (640 #mol C02 mol- 1air ) clear-plastic-wall open-top chambers. The cotton and soybean top and root results came from plants grown in identical ambient and CO2-enriched glasshouses and the tomato data from highhumidity rigid plastic greenhouses. In all instances, the plants sampled remained within their respective CO2 treatments from seeding to harvest. The actual data were obtained by weighing the various plant parts when they were first removed from the chambers or glasshouses, oven-drying them to drive out all water from their tissues, and then weighing them again and forming their dry- to fresh-weight ratios. Each top and root data point thus obtained r e p r e

173 sents the mean of from 10 to 30 A. vilmoriniana, cotton and soybean plants and from 40 to 400 carrot and radish plants; while the water fern and water hyacinth data points represent intermediate numbers between these two extremes. Each cotton-leaf data point, on the other hand, represents the mean of four leaf discs taken from each of five leaves. The tomato foliage data came from the prunings of more than 100 plants per greenhouse, and the tomato fruit data are the means of 10 fruits. RESULTS AND DISCUSSION Cummings and Jones (1918) reported percentage dry matter contents from their extensive CO2 enrichment experiments. It appears from their work (Fig. 1) that CO2 enrichment generally had little effect on plant percentage dry matter content. Their lettuce data, in particular, appear roughly evenly distributed about the one-to-one correspondence line, contrary to the suggestion of Lemon (1977, 1983) that C02 enrichment increases the water content of that crop. On the other hand, Cummings and Jones did report that their Swiss chard leaves were more succulent under C02 enrichment, the only such statement we have found in the literature. Their data for this plant in Fig. 1 fall consistently below the one-to-one correspondence line, but not by very much relative to the scatter in all the other data points. ¢/) P 52 Z ..I o. a ILl

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Fig. 4. Percentagedry matter contents of the shoots of several ornamentalplants grownat various elevated C02 concentrations from 900 to 1800 Ftmol CO2 mo1-1 air vs. those of the respective control plants grown at 300-330/~mol CO2mol- 1air. From Mortensen (1983) and Moe (1977). The percentage dry matter results for 13 species studied in subsequent CO2enrichment experiments are presented in Figs. 2-4. The general dispersion of the data about the one-to-one correspondence lines in these figures shows that CO2 enrichment generally had relatively minor effects on percentage dry matter content in these species. In particular, the lettuce data of Knecht and O'Leary (1983) are slightly above the one-to-one correspondence line and therefore also do not support Lemon's suggestion of CO2 increasing the water content of lettuce. The wheat data of Macdowall (1972) that were obtained under low-light conditions (300 ft-c or 36 zmol photons m -2 s -], Fig. 2) are consistently below the one-to-one line, but his data for higher light conditions ( > 800 ft-c or 96 #mol photons m -2 s - 1) are dispersed on both sides of it. The lateral shoot data of Moe (1977) for Campanula (Fig. 4 ) are also consistently below the one-to-one line, but only slightly, and his Campanula-cutting data are above it. Thus, except for the Swiss chard data of Cummings and Jones (1918, Fig. 1 ), we have not found any data in the prior literature that consistently supports the suggestion of CO2 enrichment increasing the water content of plant tissues. On the contrary, inspection of Figs. 1-4 suggests either no effect or a slight positive increase in percentage dry matter content with CO2-enrichment. The tomato data of Madsen (1973) (Fig. 3 ) appear to be "outliers" from the

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rest of the data and perhaps should be discarded. However, Madsen (1968) also documented high (5- to 12-fold) increases in the starch content of his tomato leaves grown under high-light summer greenhouse conditions with a high source-to-sink ratio (young plants with no fruit yet ), so perhaps his data are valid. The leaf and stem data from the study of Kimball and Mitchell ( 1979 ) were obtained from lateral shoot prunings, so their tissues were very young and may not have had time to accumulate starch. The tomato top data of Knecht and O'Leary (1974) were obtained in a growth chamber at a light intensity less than half of full sunlight, a condition probably not conducive to starch accumulation.

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Fig. 6. Same as Fig. 5, but for cotton and soybean roots and tops. Our own more recent data for radish, carrot, cotton and soybean are presented in Figs. 5 and 6. Looking first at the results for radish and carrot (for which we have the most data points of this type) we note that all of the data distributions generally follow the one-to-one correspondence line. However, the tops of both plants definitely have a greater percentage of their total data points above this line (71% above for radish and 75% above for carrot), indicative of a greater percentage dry m a t t e r content for these plant parts under CO2-enriched conditions as opposed to ambient conditions, once again in contradiction of what Lemon ( 1977, 1983 ) reported for lettuce. In the case of the roots, however, the data are much more evenly distributed, with 50% above and 50% below the one-to-one correspondence line for radish, and 51% above and 49% below for carrot.

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The same general tendency to follow the one-to-one correspondence line is apparent in the cotton and soybean data of Fig. 6. But for these plants, whose data distributions extend to greater percentage dry matter contents than do those of radish and carrot, both the tops and the roots have greater percentages of their data points above this line than below it. Our results with water hyacinth, water fern, A. vilmoriniana and cotton leaves are presented in Fig. 7. The water hyacinth, water fern and A. vilmoriniana data are all roughly evenly dispersed about the one-to-one line, whereas the cotton-leaf data fall predominantly (93% of them) above it. The most likely explanation for the cotton-leaf data (and probably tbr much of the plant shoot data) being above the one-to-one line is that C02-enrichment causes cotton plants to accumulate much more starch in their leaves (Mauney et al., 1979). Indeed, as reported by Radin et al. (1987) as part of this same experiment, predawn starch levels were five to eight times greater in leaves enriched to 640 pmol CO2 mol-1 air at dawn and two to three times greater at dusk. Since starch comprises 20-50% of the total dry weight of the leaves, such high starch accumulations with CO2 enrichment easily account for the percentage dry weight increase. Consequently, under conditions such as high light intensity or a high source-to-sink ratio, which would tend to cause starch to accumulate in leaves, one would expect CO2 enrichment to increase

179 the p e r c e n t a g e d r y m a t t e r c o n t e n t . T h i s is, in fact, w h a t we o b s e r v e d in t h e c o t t o n leaves; and, as a l r e a d y discussed, this was also p r o b a b l y t h e cause o f t h e " o u t l i e r " t o m a t o d a t a of M a d s e n (1973) (Fig. 3 ). In conclusion, t h e r e are v e r y few i n s t a n c e s w h e r e COz e n r i c h m e n t has sign i f i c a n t l y d e c r e a s e d t h e p e r c e n t a g e dry m a t t e r c o n t e n t of p l a n t tissues. In general, p l a n t p e r c e n t a g e d r y m a t t e r c o n t e n t a p p e a r s to c h a n g e b u t little with C02 e n r i c h m e n t , e x c e p t u n d e r c o n d i t i o n s t h a t t e n d to cause s t a r c h to a c c u m u l a t e in leaves (high light i n t e n s i t y , high s o u r c e - t o - s i n k ratio ). T h e n p l a n t p e r c e n t age dry m a t t e r c o n t e n t t e n d s to rise. In addition, Idso (1988) has a r g u e d t h a t COe e n r i c h m e n t also t e n d s to increase p l a n t p e r c e n t a g e d r y m a t t e r c o n t e n t as p l a n t w a t e r stress intensifies. ACKNOWLEDGMENT C o n t r i b u t i o n f r o m t h e Agricultural R e s e a r c h Service, U.S. D e p a r t m e n t of Agriculture. S u p p o r t e d in p a r t b y t h e U.S. D e p a r t m e n t of E n e r g y , C a r b o n Dioxide R e s e a r c h Division, Office of E n e r g y R e s e a r c h , u n d e r I n t e r a g e n c y A g r e e m e n t No. D E - A l I 0 1 - 8 1 E R - 6 0 0 1 . REFERENCES Acock, B., Reddy, V.R., Hodges, H.F., Baker, D.N. and McKinion, J.M., 1985. Photosynthetic response of soybean canopies to full-season carbon dioxide enrichment. Agron. J., 77: 942-947. Allen, L.H., Jr., Boote, K.J., Jones, J.W., Jones, P.H., Valle, R.R., Acock, B., Rogers, H.H. and Dahlman, R.C., 1987. Response of vegetation to rising carbon dioxide: photosynthesis, biomass, and seed yield of soybean. Global Biogeochem. Cycles, 1: 1-14. Allen, L.H., Jr., Vu, J.C.V., Valle, R.R., Boote, K.J. and Jones, P.H., 1988. Nonstructural carbohydrates and nitrogen of soybean grown under carbon dioxide enrichment. Crop Sci., 28: 8494. Allen, S.G., Idso, S.B., Kimball, B.A. and Anderson, M.G., 1988a. Interactive effects of C02 and environment on photosynthesis ofAzoUa. Agric. For. Meteorol., 42: 209-217. Allen, S.G., Idso, S.B., Kimball, B.A. and Anderson, M.G., 1988b. Relationship between growth rate and net photosynthesis of Azolla in ambient and elevated C02 concentrations. Agric. Ecosys. Environ., 20: 137-141. Cummings, M.B. and Jones, C.H., 1918. The aerial fertilization of plants with carbon dioxide. Bull. 211, University of Vermont and State Agricultural College, Vermont Agricultural Experimental Station, Free Press Printing Co., Burlington, Vermont, 56 pp. Idso, S.B., 1988. Three phases of plant response to atmospheric COe enrichment. Plant Physiol., in press. Idso, S.B., Kimball, B.A. and Anderson, M.G., 1985. Atmospheric COz enrichment of water hyacinths: effects on transpiration and water use efficiency. Water Resour. Res., 21:1787-1790. Idso, S.B., Kimball, B.A. and Anderson, M.G., 1986a. Foliage temperature increases in water hyacinth caused by atmospheric C02 enrichment. Arch. Meteorol. Geophys. Bioklimatol., Ser. B, 36: 365-370. Idso, S.B., Kimball, B.A., Anderson, M.G. and Szarek, S.R., 1986b. Growth response of a succulent plant, Agave vilmoriniana, to elevated C02. Plant Physiol., 80: 796-797. Idso, S.B., Kimball, B.A. and Mauney, J.R., 1987a. Atmospheric carbon dioxide enrichment effects on cotton midday foliage temperature: implications for plant water use and crop yield. Agron. J., 79: 667-672. Idso, S.B., Kimball, B.A., Anderson, M.G. and Mauney, J.R., 1987b. Effects of atmospheric C02

180 enrichment on plant growth: the interactive role of air temperature. Agric. Ecosys. Envir(m, 20: 1-10. Jones, P.H., Allen, L.H., Jr.. Jones, J.W., Boote, K.J. and Campbell, W.J., 1984. Soybean canopy growth, photosynthesis, and transpiration responses to whole-season carbon dioxide enrich ment. Agron. J.. 76: 633-637. Jones, P.H., Allen, L.H., Jr., Jones, J.W. and Valle, R.R., 1985. Photosynthesis and transpiration responses of soybean canopies to short- and long-term C02 treatments. Agron. J.. 77: t 19-126. Kimball, B.A., 1983a. Carbon dioxide and agricultural yield: an assemblage and analysis of 43() prior observations. Agron. J., 75: 779-788. Kimball, B.A., 1983b. Carbon dioxide and agricultural yield: an assemblage and analysis of 77(~, prior observations. WCL Rep. No. 14, U.S. Water Conservation Laboratory, Phoenix, AZ, 7 t pp. Kimball, B.A. and Mitchell, S.T., 1979. Tomato yields from C02-enrichment in unventilated and conventionally ventilated greenhouses. J. Am. Soc. Hortic. Sci., 104: 515-520. Kimball, B.A., Mauney, J.R., Guinn, G., Nakayama, F.S., Idso, S.B., Radin, J.W., Hendrix, D.L. Butler, D.G., Jr., Zarembinski, T.I. and Nixon, P.E., 1985. Effects of increasing atmospheric C02 on the yield and water use of crops, in: Response of Vegetation to Carbon Dioxide. (I.S. Department of Energy Greenbook Series, Washington DC, 027, 75 pp. Kimball, B.A., Mauney, J.R., Radin, J.W., Nakayama, F.S., Idso, S.B., Hendrix, D.L., Akey, D.H.. Hartung, W., Allen, S.G. and Anderson, M.G., 1986. Effects of increasing atmospheric CO~ on yield and water use of crops. In: Response of Vegetation to Carbon Dioxide. U.S. Department of Energy Greenbook Series, Washington DC, 039, 125 pp. Knecht, G.N., 1975. Response of radish to high C02. HortScience, 10: 274-275. Knecht, G.N. and O'Leary, J.W., 1974. Increased tomato fruit development by CO:~enrichmen~ J. Am. Soc. Hortic. Sci., 99: 214-216. Knecht, G.N. and O'Leary, J.W., 1983. The influence of carbon dioxide on the growth, pigment. protein, carbohydrate, and mineral status of lettuce. J. Plant Nutrition, 6:301-312. Lemon, E.R., 1977. The land's response to more carbon dioxide. In: N.R. Anderson and A. Ma~ lahoff (Editors), The Fate of Fossil Fuel C02 in the Ocean. U.S. Office of Naval Research. Symposium Series in Oceanography, Plenum, New York, pp. 97-130. Lemon, E.R., 1983. Interpretive summary. In: E.R. Lemon (Editor), CO,~ and Plants: The Response of Plants to Rising Levels of Atmospheric Carbon Dioxide. AAAS Selected Symposium 84, Westview Press, Boulder, CO, pp. 1-5. Lincoln, D.E., Sionit, N. and Strain, B.R., 1984. Growth and feeding response of Pseudoplusia includens (Lepidoptera: Noctuidae) to host plant grown in controlled carbon dioxide atmo spheres. Environ. Entomol., 13: 1527-1530. Lincoln, D.E., Couvet, D. and Sionit, N., 1986. Response of an insect herbivore to host plan~s grown in carbon dioxide enriched atmospheres. Oecologia, 69: 556-560. Macdowall, F.O.H., 1972. Growth kinetics of Marquis wheat. II. Carbon dioxide dependence. Can. J. Bot., 50: 883-889. Madsen, E., 1968. Effect of CO.,-concentration on the accumulation of starch and sugar in tomato, leaves. Physiol. Plant., 21: 168-175. Madsen, E., 1973. The effect of CO2-concentration on development and dry matter production in young tomato plants. Acts Agric. Scand., 23: 235-240. Mauney, J.R., Guinn, G., Fry, K.E. and Hesketh, J.D., 1979. Correlation of photosynthetic carbon dioxide uptake and carbohydrate accumulation of cotton, soybean, sunflower and sorghum. Photosynthetica, 13: 260-266. Moe, R., 1977. Effect of light, temperture, and CO2 on the growth of Campanula isophylla stock plants and on the subsequent growth and development of their cuttings. Sci. Hortic, 6:129 141. Mortensen, L.M., 1983. Effect of CO2 enrichment on photosynthesis and growth of some green-

181 house plants. Agricultural University of Norway, Department of Floriculture and Greenhouse crops. As, Norway. Osbrink, W.L.A., Trumble, J.T. and Wagner, R.E., 1987. Host suitability of Phaseolus lunata for Trichoplusia ni (Lepidoptera: Noctuidae) in controlled carbon dioxide atmospheres. Environ. Entomol., 16: 210-215. Radin, J.W., Kimball, B.A., Hendrix, D.L. and Mauney, J.R., 1987. Photosynthesis of cotton plants exposed to elevated levels of carbon dioxide in the field. Photosynthesis Res., 12: 191203. Spencer, W. and Bowes, G., 1986. Photosynthesis and growth of water hyacinth under CO2 enrichment. Plant Physiol., 82: 528-533. Swalls, A.A. and O'Leary, J.W., 1976. Growth, water consumption, and salt uptake of tomato plants in high humidity-high carbon dioxide greenhouse environments. J. Ariz. Acad. Sci., 11: 23-26.