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Effects of Atmospheric CO2 Enrichment on the Physiological and Biochemical Responses of Maize to Chilling Temperatures
Baczek-Kwinta, R. and Koscielniak, J. 2003. Anti-oxidative effect of elevated CO2 concentration in the air on maize hybrids subjected to severe chill. Photosynthetica 41: 161-165.

Maize (Zea mays L.) is a C4 plant of tropical origin; and, hence, as noted by Baczek-Kwinta and Koscielniak, "it is extremely sensitive to chill (temperatures 0-15C)." Nevertheless, maize is often grown in cool temperate zones because of its high yield potential; but in such circumstances it can experience a variety of maladies associated with exposure to periods of chilling air temperatures.

What was done
The authors grew two hybrid genotypes - KOC 9431 (chill-resistant) and K103xK85 (chill-sensitive) - from seed in air of either ambient (350 ppm) or elevated (700 ppm) CO2 concentration (AC or EC, respectively), after which the plants were exposed to air of 7C for eleven days and then recovered in ambient air of 20C for one day. Throughout this period, a number of physiological and biochemical parameters were measured on the plants' third fully-expanded leaves.

What was learned
Baczek-Kwinta and Koscielniak report that "EC inhibited chill-induced depression of net photosynthetic rate (PN), especially in leaves of chill-resistant genotype KOC 9431," which phenomenon "was distinct not only during chilling, but also during the recovery of plants at 20C." In fact, they note that "seedlings subjected to EC showed 4-fold higher PN when compared to AC plants." They also determined that "EC diminished the rate of superoxide radical formation in leaves in comparison to the AC control." In addition, they say that "electrolyte leakage from the [leaf membrane] tissue, a parameter reflecting membrane injury, was significantly lower in samples of plants subjected to EC than AC." Last of all, they report that enrichment of air with CO2 successfully inhibited the decrease in the maximal quantum efficiency of photosystem 2, both after chilling and during the one-day recovery period.

What it means
Lumping all of these positive effects of elevated CO2 together, the authors conclude their paper by saying that "the increase in atmospheric CO2 concentration seems to be one of the protective factors for maize grown in cold temperate regions."

Reviewed 4 February 2004