Elevated carbon dioxide exacerbates adverse effects of Mg deficiency in durum wheat

Background and Aims Elevated carbon dioxide (CO2) and magnesium (Mg) deficiency have contrasting influences on plant growth and performance, but disrupt carbohydrate metabolism in a similar manner. This study was aimed at characterizing interactive effects of elevated CO2 and Mg nutrition on carbohydrate metabolism, sink strength and biomass partitioning. Methods Durum wheat was cultured in climate chambers with ambient (398 μmol mol−1 air) or elevated CO2 (700 μmol mol−1 air) and with adequate (1000 μM) or low (75 μM) Mg supply in nutrient solution. Biomass production and partitioning, tissue Mg concentrations, photosynthetic performance and carbohydrate status of leaves and roots were determined. Results Low-Mg plants responded to elevated CO2 with a biomass decrease rather than enhancement especially in roots. In low-Mg plants inhibition of root growth and partitioning of biomass towards shoots were enhanced by elevated CO2. Elevated CO2 increased photosynthesis rate in adequate-Mg plants, but not in low-Mg plants. Leaf carbohydrate concentration was increased 2 fold by low Mg at ambient CO2 and 3 fold at elevated CO2, suggesting that low Mg and elevated CO2 decreased carbohydrate transport from source tissues. Conclusions Elevated CO2 exacerbated adverse effects of inadequate Mg nutrition on plant growth, biomass partitioning, carbohydrate metabolism and photosynthetic performance in durum wheat. Adequate Mg nutrition was important for maintaining efficient transport of carbohydrates and thus prevent an early acclimation to elevated CO2. Keywords Elevated carbon dioxide Magnesium Whea