Paper Reviewed
Zhu, X., Liu, S., Sun, L., Song, F., Liu, F. and Li, X. 2018. Cold tolerance of photosynthetic electron transport system is enhanced in wheat plants grown under elevated CO2. Frontiers in Plant Science 9: 933, doi: 10.3389/fpls.2018.00933.

Although a number of studies have examined the combined impact of elevated CO2 and high temperature stress on the growth and development of plants, few studies have investigated the interactive effects of elevated CO2 and low temperature stress. However, low temperature stress, according to Zhu et al. (2018), is "one of the most critical environmental stimuli affecting crop plant growth and grain yield. Seeking more information on this topic, Zhu et al. set out to study the impact of elevated CO2 and low temperature stress on wheat (Triticum aestivum).

Writing as background for their work, the six scientists state that wheat is "very sensitive to low temperature stress during the reproductive stage." Such stress occurs from cold-induced damage to the photosynthetic apparatus, as low temperatures increase membrane viscosity and restrict the diffusion of plastoquinone, which inhibits thylakoid electron transport. Such inhibition over-energizes the thylakoid membranes and leads to an overproduction of reactive oxygen species that induce photodamage. It was the authors' hypothesis that elevated CO2 would enhance photosynthetic and antioxidant systems and thereby mitigate the effects of low temperature stress.

To test this hypothesis, Zhu et al. grew wheat (cv Lianmai6) in pots in a controlled-environment facility under ambient (400 ppm) or elevated (800 ppm) CO2 for five months. At the head emerging stage, half of the wheat plants in each CO2 treatment were subjected to a low temperature stress treatment of 2/-1°C day/night for a period of two days.

Results of the cold stress treatment revealed that low temperatures indeed depressed photosynthesis, primarily due to negative effects on the photosynthetic electron transport system. However, the authors report that wheat grown under elevated CO2 "had a higher efficiency in photosynthetic electron transport than wheat under ambient CO2." What is more, they observed that "wheat plants grown under elevated CO2 possessed higher reactive oxygen species scavenging capacity than that under ambient CO2, which benefited for the protection of photosynthetic electron transport system."

Taken together, the above findings demonstrate that rising CO2 levels will help reduce the negative impacts of cold temperature stress on winter or spring wheat. And those benefits will translate to greater growth and yields.