ObjectivesReaumuria soongorica is a dominant desert steppe plant in the arid region of China. The objective of the study was to evaluate the interaction of elevated CO₂ concentration and precipitation on root morphology and root function of the desert plant, to provide scientific reference for the growth of R. soongorica under the background climate change in the future.

MethodsA pot experiment was conducted with three CO₂ concentrations (350, 550 and 700 μmol/mol) and five precipitation levels. Taking the local natural precipitation as control (100%), precipitation of 30% less (–30%), 15% less (–15%), 15% more (+15%) and 30% more (+30%) were designed. The total root length, total root surface area, total root volume, root average diameter, root biomass, root/shoot ratio, specific root length, specific root area, carbon content, nitrogen content and C/N of R.soongorica. were investigated.

ResultsThe total root length, total root surface area, root biomass and average diameter of R. soongorica were significantly affected by both the CO₂ concentration and precipitation and their interaction (P < 0.01), while the root/shoot ratio, specific root length and specific root area of R. soongorica were significantly affected by CO₂ concentration and precipitation (P < 0.01), but not by the synergetic effects. The increases of total root length, total root surface area, total root volume and root average diameter under the –30% and –15% less precipitation treatments were averagely18.53% higher than those under the +15% and +30% more treatments (P < 0.05),while the root biomass under the +15% and +30% treatments were120.8% higher than those under the –30% and –15% less treatments. The root/shoot ratios under the –30% and –15% less treatments were 57.1% higher than those under the +15% and +30% more treatments(P < 0.01), and the root/shoot ratios in all the precipitation treatments were significantly decreased by the elevated CO₂ concentration. The specific root length and specific root area were decreased significantly with the precipitation increased from –30% to +30%, and they were increased obviously by the elevated CO₂ concentration. The carbon and nitrogen contents were increased significantly with the precipitation increased from –30% to +30%. Under the high CO₂ concentration, the carbon content was increased and nitrogen content was decreased. The C/N ratios in roots of R. soongoricawere were significantly increased under the high CO₂ concentration, and there was a fluctuant variation of C/N according to the precipitation increased.

ConclusionsThe elevation of CO₂ concentration has a positive effect on root morphology indexes except the root/shoot ratio. Under the high CO₂ concentration, the total root length, total root volume, root average diameter, root/shoot ratio, specific root length and specific root area are significantly affected by low precipitation, while the total root surface area and root biomass are affected by the high precipitation. The root C/N of R. soongorica has positive response to the elevated CO₂ concentration, while the response of C/N to the interaction of CO₂ and precipitation will not be predicted, depending on the different CO₂ concentration and precipitation.