ABSTRACT Terminal drought is a primary constraint to wheat production in Mediterranean environments, often severely reducing grain weight and quality. This study evaluated the physiological contribution of awns to yield formation, water use efficiency (WUE), and grain quality traits in bread wheat Triticum aestivum L. and durum wheat Triticum turgidum subsp. durum (Desf.) Husn.. Two field experiments were conducted in Izmir, Turkey, over the 2018–2019 and 2022–2023 growing seasons under rainfed and supplemental irrigation conditions. Treatments consisted of intact spikes and manually de‐awned spikes to assess the net photosynthetic and metabolic contribution of awns. De‐awning significantly reduced grain yield and thousand‐grain weight in both species, though the magnitude of loss was influenced by water availability. In durum wheat, a significant Awn × Irrigation interaction ( p < 0.01) for yield suggested that awns play a more critical compensatory role in durum cultivars under water stress compared to bread wheat. Physiologically, awns contributed to maintaining higher WUE and, in bread wheat, supported grain protein accumulation. However, the presence of awns tended to reduce the concentration of essential amino acids, likely due to the dilution effect resulting from increased carbohydrate accumulation. Awn removal reduced protein content in T. aestivum but not T. durum , yet increased essential amino acid concentrations in both species, likely reflecting a concentration effect due to reduced yield. These findings confirm that awns serve as a vital photosynthetic organ during terminal drought, playing a decisive role in sustaining yield and regulating the carbon‐nitrogen balance in Mediterranean wheat cultivation.
Yeşil et al. (2026) studied this question.