The decline in leaf mesophyll conductance is derived from anatomical traits under multiple stresses of water, salt and high temperature in cotton.

Climate change-driven extreme abiotic environmental stresses, for instance water stress, salt stress, and high temperature, prominently threaten agricultural crop development and yield. Although we have extensive knowledge regarding how plants react to each of these single stresses, we have limited understanding of how the combination of multiple factors (i.e., multiple stresses) have impact on leaf CO2 diffusion and photosynthesis. This study examined the response of leaf mesophyll conductance (gm) and its consequences for photosynthesis and biomass in flower and boll stages of cotton under the multiple stresses of water, salt, and high temperature. The results revealed that the multiple stresses of water, salt, and high temperature stress markedly reduced stomatal conductance (gs), gm and net photosynthesis rate (AN), and AN was positively associated with gs and gm. The decline in gm was closely associated with reductions in the surface areas of mesophyll cells and chloroplasts exposed to intercellular airspace. Under triple stress, gm showed a great decline than under individual stresses, whereas the reduction in AN was comparatively less pronounced. This discrepancy is likely because biochemical limitations became the dominant factor under severe stress. These findings demonstrate that the multiple stresses of water, salt, and high temperature obviously restricts gm and impairs photosynthetic capacity by changes in leaf anatomical traits, it suggests that optimizing CO2 diffusion may represent a potential strategy to mitigate the effect of multiple stresses.