C and N allocation on wheat under the effects of depleted, current andelevated [CO2] are modulated by water availability

Abstract

Although elevated atmospheric [CO2] has substantial indirect effects on vegetation carbon uptake via associatedclimate change, their dynamics remain unclear. The carbon and nitrogen allocation and partitioning in durumwheat were compared at different [CO2] and different water availability. The aim of this study was to investigatehow the impacts of depleted and elevated [CO2] driven climate change on Mediterranean wheat plants underdrought conditions. For that reason, double stable isotope labelling using 13CO2 and 15NH4–15NO3 was conductedto follow 13C and 15N allocation and partitioning in the different plant organs. Plants were studied in growthchambers under three different CO2 environments (depleted, current and elevated) and two water availabilityconditions (well-watered and mild-water-stress). Isotopic 13C and 15N determination, gas exchange analyses andgrowth parameters were measured.We show that plants subjected to depleted and elevated [CO2] suffered up and down regulation of photosynthesisrespectively, but their responses were both modulated by water availability. Depleted [CO2] anddrought reduced plant biomass. However, elevated [CO2], show that the initial positive effect of elevated [CO2]on carbon uptake declined rapidly, showing a consequence of physiological acclimation and the inhibition of[Rubisco] and activity, this effect was more evident in combination with drought. In both cases, depleted [CO2]and elevated [CO2] condition modified the C and N allocation compared with current [CO2], overall combinedwith drought.These results obtained highlight the different C and N management strategies of wheat and provide relevantinformation about the potential response of plants under global climate change conditions