From CO2Science: Writing as background for their study, Shimomura et al. (2020) note that chlorogenic acid (CGA) is “a strong antioxidant that potentially reduces oxidative damage in human cells.” Its production in plants is a function of various environmental factors, including temperature, salinity, atmospheric CO2 concentration and light conditions. And so in recognition of the above facts, Shimomura et al. set out to explore the relationship between CO2 and light intensity in the production of CGA in young lettuce plants.
Paper reviewed: Shimomura, M., Yoshida, H., Fujiuchi, N., Ariizumi, T. Ezura, H. and Fukuda, N. 2020. Continuous blue lighting and elevated carbon dioxide concentration rapidly increase chlorogenic acid content in young lettuce plants. Scientia Horticulturae 272: 109550, doi.org/10.1016/j.scienta.2020.109550.
Their experiment was conducted in controlled growth chambers where two-week-old green lettuce (Lactuca sativa, cv. Green Wave) seedlings were subjected to a full-factorial design of four atmospheric CO2 concentrations and three light intensities for a period of one week, after which they were harvested and examined for CGA content. The four CO2 levels included 400, 1000, 1500 and 2000 ppm, while the three light intensities were 100, 200 and 300 µmol m-2 s-1 photosynthetic photon flux density, which were irradiated by white fluorescent lamps that provided continuous lighting.
In discussing their findings the authors note that “elevated CO2 concentration led to increased lettuce growth with higher dry matter weight than the control treatment” (increases up to 68% as seen in Figure 1). More importantly, it stimulated the production of CGA. As shown in Figure 1 the CGA content per lettuce dry matter increased by 196%, 146% and 175% in the 1000, 1500 and 2000 ppm CO2 treatments, respectively. Shimomura et al. additionally found that plant growth and CGA content increased in response to increasing light intensity and that there was a “compound effect” on these enhancements when CO2 and light intensity increased together. Consequently, in light of the above, it would appear that as the air's CO2 concentration rises in the years and decades ahead, the chlorogenic acid content of lettuce will increase, producing more of this effective antioxidant for human consumption and health care. And that is good news worth reporting.
Figure 1. Top dry matter weight (green columns) and CGA content per dry weight (blue columns) of lettuce seedlings grown at different atmospheric CO2 concentrations. Data presented originate from Table 1 of Shimomura et al. (2020).