Leaf nitrogen have a better relationship with photosynthesis performance across wheat species under elevated CO and drought.

Elevated CO concentrations and persistent drought are predicted to inhibit the photosynthetic performance and yield of crops. Such effects vary considerably between species groups. Modern cultivated (Triticum aestivum L., AABBDD) and wild (Triticum dicoccoides Korn L., AABB and Triticum monococcum L., AA) species of wheat were subjected to elevated CO concentration (ambient concentration +200 μmol mol) and drought (well watered: 75-85% of the field water capacity; drought: 50-60% of the field water capacity) at open-top chamber experimental facilities. Elevated CO concentration decreased the limitation of stomatal morphology traits on stomatal conductance regulation. This could compensate the disadvantage of plants who has low stomatal density and large single stomatal area as well as low leaf water use efficiency such as modern wheat Z9023 in drought acclimation in the future CO rising world. Moreover, elevated CO concentration largely increased the dependence of light harvesting and electron transportation performance per photosynthesis system II reaction center, maximum rubisco carboxylation rate, and maximum Ribulose-1,5-bisphosphate regeneration rate on leaf nitrogen concentration across the selected wheat species and water regimes. Modern cultivated cultivars Z9023 and CH58 have higher photosynthetic performance per unit of leaf nitrogen than wild species under elevated CO concentrations. The increasing CO may present opportunities to breeders and possibly allow them to select for cultivars with better photosynthetic nitrogen use efficiency response to future CO rising climate.