Paper Reviewed
Brand, D., Wijewardana, C., Gao, W. and Reddy, K.R. 2016. Interactive effects of carbon dioxide, low temperature, and ultraviolet-B radiation on cotton seedling root and shoot morphology and growth. Frontiers in Earth Science 10: 607-620.

In providing the rationale for their study, authors Brand et al. (2016) note that while many studies have examined the impact of elevated CO2, temperature and UV-B radiation as single stressors on cotton plants, until now there has been no study that has examined the combined effects of these stresses. It therefore became their objective to remedy this data deficiency by investigating "the interactive effects of CO2, UV-B radiation, and low temperature on root morphology and early seedling vigor of [four] cotton cultivars."

Their work was conducted at the Rodney Foil Plant Science Research facility located at Mississippi State University, where they grew four cultivars of cotton in controlled sunlit growth chambers for 20 days following seedling emergence. In all, eight treatments were utilized to examine the interactive growth effects, including two CO2 concentrations (400 or 750 ppm), two temperatures (28/20°C or 21/12°C) and two UV-B levels (0 or 10 kJ m^-2 d^-1 between 0800 and 1600 hours each day). The control treatment was set at 400 ppm CO2, 28/20°C day/night temperature (which was the higher of the two temperature treatments) and 0 kJ m^-2 d^-1 UV-B.

In describing their findings, Brand et al. report that the "vegetative growth of all cotton cultivars including root morphology traits was negatively influenced by low temperature and increased UV-B treatment, but it was positively influenced by elevated CO2," which elevation "increased the total biomass production significantly in all four cotton cultivars tested." Elevated CO2 also "stimulated root growth," producing longer, thicker and highly branched roots, while low temperature and elevated UV-B "either individually or in combination, suppressed most root traits" (see figure below).

In light of the above findings, it is safe to conclude that cotton plants will benefit from rising atmospheric CO2 concentrations, and those benefits will help to reduce the deleterious impacts of growth-related stresses caused by low temperature and elevated UV-B radiation.

Figure 1. Representative scanned root images from single and combined stress treatments for two cotton cultivars (DP1522B2XF and TM-1) harvested at 20 d after planting. Source: Brand et al. (2016). Treatment legend: +CO2 = elevated CO2, -T = low temperature, +UV-B = elevated UV-B.