Many and varied are the studies that have demonstrated the pervasive positive influence of elevated levels of atmospheric CO2 on the photosynthetic prowess of wheat (Triticum aestivum L.). For several examples of this fact of plant life, see wheat, photosynthesis, in the Plant Growth Data section of our website. In addition, we here briefly summarize the findings of the subset of those studies for which we have produced Journal Reviews.
Monje and Bugbee (1998) grew wheat hydroponically in controlled environment chambers maintained at atmospheric CO2 concentrations of 330 and 1200 ppm, finding that plants grown at the elevated CO2 concentration exhibited net photosynthesis rates that were 13% greater than those of the ambiently-grown plants over most of their life cycle. Bunce (1998), on the other hand, grew winter wheat in field plots for two full growing seasons, documenting a CO2 fertilization effect that rose from 63% at an air temperature of 10°C to 115% at an air temperature slightly above 30°C when the CO2 concentration of the air surrounding the leaf being measured was briefly doubled.
In a more realistic situation, Garcia et al. (1998) grew spring wheat in the field near Maricopa, Arizona, USA, from emergence to maturity in FACE plots exposed to air of either 370 or 550 ppm CO2, finding that the extra 180 ppm of CO2 increased the average midday rate of net photosynthesis by 28%. Similarly, Hakala et al. (1999) grew spring wheat in the field at Jokioinen in the southern part of Finland for a period of three years in open-top chambers maintained at ambient and elevated (700 ppm) atmospheric CO2 concentrations, documenting a CO2-induced enhancement of net photosynthesis in the range of 31-37%.
Liu et al. (2002) grew three widely-cultivated varieties of winter wheat (Jingdong 8, Nongda 139, and Yanda 1817) in fields near Beijing, China, subjecting them to a short-term doubling of the air's CO2 content and observing photosynthetic enhancements of 173% (Jingdong 8), 88% (Nongda 139) and 76% (Yanda 1817). Srivastava et al. (2002), on the other hand, grew wheat plants in pots within open-top chambers maintained at atmospheric CO2 concentrations of 350 and 600 ppm for several months. Measuring net photosynthetic rates at 9:30, 13:30 and 17:30 local time during the vegetative growth stage of the plants, they documented CO2-induced increases of 125%, 27% and 33%, respectively, while during the flowering growth stage they measured increases of 108%, 23% and 0%, respectively. Last of all, Harnos et al. (2002) grew winter wheat in open-top chambers maintained for an entire growing season at atmospheric CO2 concentrations of 365 and 700 ppm, finding that the twice-ambient CO2 concentration increased net photosynthesis rates by approximately 100% in upper-canopy leaves and by 770% in leaves further down in the canopy, where light intensity was 60% less than in the upper canopy.
In light of these several observations, it should be clear to most everyone that in a wide variety of circumstances, atmospheric CO2 enrichment tends to significantly increase the photosynthetic rates of wheat plants.
Bunce, J.A. 1998. The temperature dependence of the stimulation of photosynthesis by elevated carbon dioxide in wheat and barley. Journal of Experimental Botany 49: 1555-1561.
Garcia, R.L., Long, S.P., Wall, G.W., Osborne, C.P., Kimball, B.A., Nie, G.Y., Pinter Jr., P.J., LaMorte, R.L. and Wechsung, F. 1998. Photosynthesis and conductance of spring-wheat leaves: field response to continuous free-air atmospheric CO2 enrichment. Plant, Cell and Environment 21: 659-669.
Hakala, K. Helio, R., Tuhkanen, E. and Kaukoranta, T. 1999. Photosynthesis and Rubisco kinetics in spring wheat and meadow fescue under conditions of simulated climate change with elevated CO2 and increased temperatures. Agricultural and Food Science in Finland 8: 441-457.
Harnos, N., Tuba, Z. and Szente, K. 2002. Modelling net photosynthetic rate of winter wheat in elevated air CO2 concentrations. Photosynthetica 40: 293-300.
Liu, H.Q., Jiang, G.M., Zhang, Q.D., Sun, J.Z., Guo, R.J., Gao, L.M., Bai, K.Z. and Kuang, T.Y. 2002. Gas exchange responses to CO2 concentration instantaneously elevated in flag leaves of winter wheat cultivars released in different years. Photosynthetica 40: 237-242.
Monje, O. and Bugbee, B. 1998. Adaptation to high CO2 concentration in an optimal environment: radiation capture, canopy quantum yield and carbon use efficiency. Plant, Cell and Environment 21: 315-324.
Srivastava, A.C., Khanna, Y.P., Meena, R.C., Pal, M. and Sengupta, U.K. 2002. Diurnal changes in photosynthesis, sugars, and nitrogen of wheat and mungbean grown under elevated CO2 concentration. Photosynthetica 40: 221-225.