Effects of elevated CO2 concentration on growth and photosynthesis of Chinese yam under different temperature regimes

Effects of elevated CO2 concentration on growth and photosynthesis of Chinese yam under different temperature regimes. Nguyen Cong Thinh, Hiroyuki Shimono, Etsushi Kumagai & Michio Kawasaki.  Plant Production Science, Volume 20, 2017 - Issue 2, Pages 227-236, http://dx.doi.org/10.1080/1343943X.2017.1283963

Abstract: Chinese yam (‘yam’) was grown at different carbon dioxide concentrations ([CO2]), namely, ambient and elevated (ambient + 200 μmol mol−1), under low- and high-temperature regimes in summer and autumn, separately. For comparison, rice was also grown under these conditions. Mean air temperatures in the low- and high-temperatures were respectively 24.1 and 29.1 °C in summer experiment and 20.2 and 24.9 °C in autumn experiment. In summer experiment, yam vine length, leaf area, leaf dry weight (DW), and total DW were significantly higher under elevated [CO2] than ambient [CO2] in both temperature regimes. Additionally, number of leaves, vine DW, and root DW were significantly higher under elevated [CO2] than under ambient [CO2] in the low-temperature regime. In autumn experiment, tuber DW was significantly higher under elevated [CO2] than under ambient [CO2] in the high-temperature regime. These results demonstrate that yam shows positive growth responses to elevated [CO2]. Analysis of variance revealed that significant effect of [CO2] × air temperature interaction on yam total DW was not detected. Elevated-to-ambient [CO2] ratios of all growth parameters in summer experiment were higher in yam than in rice. The results suggest that the contribution of elevated [CO2] is higher in yam than in rice under summer. Yam net photosynthetic rate was significantly higher under elevated [CO2] than under ambient [CO2] in both temperature regimes in summer. Elevated [CO2] significantly affected on the rate in yam but not in rice in both experiments. These findings indicate that photosynthesis responds more readily to elevated [CO2] in yam than in rice.

Keywords: Chinese yam, elevated CO2, nagaimo, photosynthesis, rice

My comment: First of all, this is not news, we already knew this for these and other cultivars. Second, referring to yam in the summer experiment, "number of leaves, vine DW, and root DW were significantly higher" means 38-61 pct for high [CO2], and 40-83pct for higher temperature + higher [CO2] (they interactuate strongly). Third, as to yam in autumn and rice in both summer and autumn, the results are positive but much smaller (7-36 pct). Fourth, not all cultivars of economic interest will grow more with higher temperatures or higher [CO2], but many do. These two, yam and rice, are important cases.