Ear photosynthetic anatomy effect on wheat yield and water use efficiency

The screening of C-4 property in C-3 crops is an alteration that could improve photosynthetic capacity and efficiency, enhancing potential grain yield, particularly under water stress conditions. The present study aimed to determine how photosynthetic anatomy affects wheat (Triticum aestivum) photosynthetic rate and yield. Gas exchange and anatomical characteristics of the flag leaf and ear were compared in different ploidy wheats (diploid, tetraploid, and hexaploid) under well-watered (WW) and water-stressed (WS) conditions. The photosynthetic rate of the ear (P-N_ear) decreased to a lesser extent than that of the flag leaf (P-N_leaf) under WS and that the P-N_ear of tetraploid wheat decreased the least. Furthermore, the integral water-use efficiency (WUEi) of tetraploid wheat increased the most among the three wheat species. The anatomical characteristics varied not only between the WW and WS conditions but also between the three wheat species; tetraploid species showed higher stomatal frequency (SF), stomatal area per organ area (SA), vein distance (D-V), and bundle-sheath cell number (N-BS), and lower vein distance in the glume and lemma. Correlation analysis showed that grain yield presented significant positive correlation with the P-N_leaf, P-N_ear, and WUEi. The P-N_leaf was affected by stomatal length (SL), stomatal width, and SA, while the P-N_ear was affected by SF, SA, and stomatal size in the ear organs. The WUEi was generally positively correlated with SL, N-V, and N-BS in the ear organs. The higher vein density and well-developed bundle sheath of tetraploid species may contribute to the higher P-N_ear and lower decrease in grain yield.