Effect of CO2 enrichment on non‐structural carbohydrates in leaves, stems and ears of spring wheat

Abstract

Field‐grown spring wheat (Triticum aestivum L. cv. Dragon) was exposed to ambient and elevated CO2 concentrations (1.5 and 2 times ambient) in open‐top chambers. Contents of non‐structural carbohydrates were analysed enzymatically in leaves, stems and ears six times during the growing season. The impact of elevated CO2 on wheat carbohydrates was non‐significant in most harvests. However, differences in the carbohydrate contents due to elevated CO2 were found in all plant compartments. Before anthesis, at growth stage (GS) 30 (the stem is 1 cm to the shoot apex), the plants grown in elevated CO2 contained significantly more water soluble carbohydrates (WSC), fructans, starch and total non‐structural carbohydrates (TNC) in the leaves in comparison with the plants grown in ambient CO2. It is hypothesised that the plants from the treatments with elevated CO2 were sink‐limited at GS30. After anthesis, the leaf WSC and TNC contents of the plants from elevated CO2 started to decline earlier than those of the plants from ambient CO2. This may indicate that the leaves of plants grown in the chambers with elevated CO2 senesced earlier. Elevated CO2 accelerated grain development: 2 weeks after anthesis, the plants grown in elevated CO2 contained significantly more starch and significantly less fructans in the ears compared to the plants grown in ambient CO2. Elevated CO2 had no effect on ear starch and TNC contents at the final harvest. Increasing the CO2 concentration from 360 to 520 μmol mol−1 had a larger effect on wheat non‐structural carbohydrates than the further increase from 520 to 680 μmol mol−1. The results are discussed in relation to the effects of elevated CO2 on yield and yield components.