Does a Large-Ear Wheat Cultivar Benefit More from Elevated CO2 than a Multiple-Ear Wheat for the Utilization of Non-Structural Carbohydrates?

The effects of elevated CO₂ concentration (eCO₂) on the utilization of carbohydrates in wheat cultivars with different ear types remain poorly understood, despite the critical role of wheat ears as major carbohydrate sinks and the importance of ear type as a key growth trait influencing crop yield. In this study, a free-air CO₂ enrichment (CAAS-FACE) facility was utilized to investigate the effects of eCO₂ on the non-structural carbohydrate (NSC) utilization in two wheat cultivars: a large-ear cultivar (cv. Shaanhan 8675) and a multiple-ear cultivar (cv. Triumph). The findings demonstrated that under eCO₂ conditions, Shaanhan 8675 exhibited enhanced NSC availability and more efficient remobilization from vegetative organs to grains. This improvement was associated with sustained photosynthetic activity in the leaves during the grain-filling period, which contributed to better grain filling. Consequently, both grain NSC accumulation and kernel weight were significantly increased in Shaanhan 8675 under eCO₂. In contrast, the grain NSC accumulation in Triumph was constrained by limited translocation of NSC from the stem and ear to the grain under eCO₂ environment. Overall, our findings suggest that CO₂ enrichment has a pronounced positive effect on NSC utilization in large-ear wheat cultivars. These results contribute to strategies aimed at ensuring stable and high wheat yields under future climatic conditions.