Interactive Effects of CO2 and Drought Stress on Millet

Paper Reviewed Nematpour, A., Eshghizadeh, H.R. and Abraheh, M. 2019. Interactive effects of CO2 and nitrogen supply on growth and physiological traits of millet cultivars under drought stress. Archives of Agronomy and Soil Science 44: doi.org/10.1080/03650340.2019.1631450. According to Nematpour et al. (2019), it is “essential to gain a better understanding of the interactive effects of elevated CO2 levels and drought stress on crop yield in order to ensure future food security.” And as their contribution to this effort, the three agronomists from Iran investigated the interactive effects of CO2, drought and nitrogen supply on two millet cultivars. Their work was conducted in a controlled-environment greenhouse at the College of Agriculture, Isfahan University of Technology, Isfahan, Iran. CO2 treatments included ambient (390 ppm) and elevated (700 ppm), nitrogen (N) treatments included no N added and 85 mg N kg-1 soil applied, and the two water treatments were irrigation after 40% depletion of available soil water (adequate water) and irrigation after 75% water depletion of available soil water (water stress), which drought stress was only applied after the plant reach full establishment at the four-leaf stage. The two millet cultivars included common millet (Panicum miliaceum cv. Pishahang) and foxtail millet (Setaria italica cv. Bastan). Drought stress resulted in negative impacts on the two millet cultivars. In the words of the authors, it decreased the shoot dry weight “mainly due to such effects as increased reactive oxygen species production, damage to cell membranes, and decreased chlorophyll content and leaf area.” Elevated CO2, on the other hand, was shown to “to ameliorate the adverse effects of drought stress by reducing reactive oxygen species generation, which ultimately reduced the need for antioxidant enzymes.” In addition, elevated CO2 enhanced chlorophyll content, leaf area, and root dry weight under both well-watered and drought-stressed conditions, but the enhancements were slightly greater under well-watered conditions. More specifically, these parameters were enhanced by 38, 43, 42 and 47% for chlorophyll a, chlorophyll b, leaf area and root dry weight, respectively, under well-watered conditions and by 27, 23, 10 and 35% under drought-stressed conditions, again respectively. Shoot dry weights, reported as a mean for both cultivars, increased by 26% due to CO2 enrichment. The results of this study demonstrate that the power of atmospheric CO2 to stimulate plant growth under both adequate water and water-stressed conditions is not limited to plants utilizing the C3 photosynthetic pathway. As a C4 plant, millet also benefitted to a similar degree to that observed in most C3 plants. And that is great news for those who grow and consume this crop, especially in arid and semi-arid regions. This article appeared on the CO2 Science website at http://www.co2science.org/articles/V23/feb/a9.php]]>

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