Short-term effects of elevated atmospheric CO2 on root dynamics of water-stressed maize

The interactions between elevated [CO 2 ] and drought result in complex changes in plant root system, which challenge our current understanding.To test the effects of complex environment on plants short-term root/shoot relation with elevated [CO 2 ], maize (Zea mays) was planted to experience combined elevated [CO 2 ](380 or 750 µmol mol -1 , climate chamber), osmotic stress (15% PEG-6000). During the growing period, the root morphology, carbon (C) and nitrogen (N) concentrations, and biomass accumulation of the maize plants were investigated. Compared to water-stressed maize in atmospheric [CO 2 ], the maize subject to elevated [CO 2 ] and water stress significantly increased their total biomass accumulation throughout the experiment period, but increased their root biomass only in the early drought stressed days. The short-term increase of root biomass mainly resulted from improved specific nodal root volumes and C and N concentrations. Beyond the early drought stressed days, different levels of [CO 2 ] caused root growth to take different strategies. With elevated [CO 2 ], maize increased its nodal root volumes to extend nodal root system, but with ambient [CO 2 ], maize increased its specific seminal root volume more significantly. The study demonstrated that maize was found capable of biomass accumulation with elevated [CO 2 ] by regulating its root morphology and C and N concentrations and this could partially alleviate drought stress that it suffered.