Salinity effects on leaf anatomy: consequences for photosynthesis

Increasing salinity led to substantially higher ratios of mesophyll surface area to leaf area (A^mes/A) for Phaseolus vulgaris and Gossypium hirsutum and a smaller increase for Atriplex patula, a salt-tolerant species. The increase in internal surface for CO₂ absorption did not lead to higher CO₂ uptake rates, since the CO₂ resistance expressed on the basis of mesophyll cell wall area (r_cell) increased even more with salinity. The differences among species in the sensitivity of photosynthesis to salinity in part reflect the different A^mes/A and r_cell responses.