Wheat Seedling Flavonoid Concentrations
Levine, L.H., Kasahara, H., Kopka, J., Erban, A., Fehrl, I., Kaplan, F., Zhao, W., Littell, R.C., Guy, C., Wheeler, R., Sager, J., Mills, A. and Levine, H.G. 2008. Physiologic and metabolic responses of wheat seedlings to elevated and super-elevated carbon dioxide. Advances in Space Research 42: 1917-1928.
Against this backdrop, Levine et al. (2008) grew well watered and fertilized wheat plants (Triticum aestivum, cv Yocoro roho) from seed in custom-designed root modules -- "consisting of a porous tube embedded in Turface (1-2 mm particle size) substrate containing 5 g Osmocote time release fertilizer per liter" -- which were housed in Plexiglas chambers maintained at atmospheric CO2 concentrations of either 400, 1500 or 10,000 ppm for periods of 14, 21 and 28 days, while measuring a number of plant metabolic properties, among which were the leaf concentrations of several flavonoids capable of scavenging ROS.
The thirteen researchers report that "elevated CO2 promoted the accumulation of secondary metabolites (flavonoids) progressively to a greater extent as plants became mature." As best as can be determined from the bar graphs of their results, for example, the percentage increase in total wheat leaf flavonoid concentration in going from an atmospheric CO2 concentration of 400 to 1500 ppm was 22%, 38% and 27% (the one exception to this general rule) at 14, 21 and 28 days after planting, respectively, while in going from a CO2 concentration of 400 to 10,000 ppm, the percentage increase in total flavonoid concentration was 38%, 56% and 86%, respectively, at 14, 21 and 28 days after planting. In addition, they found that "both elevated CO2 levels resulted in an overall 25% increase in biomass over the control plants."
In addition to the potential for the types of benefits described in the background material of this review, the U.S., Japanese and German scientists write that "the increased accumulation of secondary metabolites in plants grown under elevated CO2 may have implications regarding plant-herbivore interactions, decomposition rates for inedible biomass, and potential beneficial effects on plant tolerance to water stress (Idso, 1988) and cold stress (Solecka and Kacperska, 2003) due to their potentials for the scavenging of reactive oxygen species (ROS)."
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