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

Abstract

Although elevated atmospheric [CO₂] has substantial indirect effects on vegetation carbon uptake via associated climate change, their dynamics remain unclear. The carbon and nitrogen allocation and partitioning in durum wheat were compared at different [CO₂] and different water availability. The aim of this study was to investigate how the impacts of depleted and elevated [CO₂] driven climate change on Mediterranean wheat plants under drought conditions. For that reason, double stable isotope labelling using ¹³CO₂ and ¹⁵NH₄–¹⁵NO₃ was conducted to follow ¹³C and ¹⁵N allocation and partitioning in the different plant organs. Plants were studied in growth chambers under three different CO₂ environments (depleted, current and elevated) and two water availability conditions (well-watered and mild-water-stress). Isotopic ¹³C and ¹⁵N determination, gas exchange analyses and growth parameters were measured.

We show that plants subjected to depleted and elevated [CO₂] suffered up and down regulation of photosynthesis respectively, but their responses were both modulated by water availability. Depleted [CO₂] and drought 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 combined with drought.

These results obtained highlight the different C and N management strategies of wheat and provide relevant information about the potential response of plants under global climate change conditions.