Figure 4.

Chloride (Cl⁻) nutrition at macronutrient levels significantly increases the size of leaf cells, resulting in a reduction in stomatal density and, therefore, conductance (g_s). At the same time, Cl⁻ improves mesophyll diffusion conductance to CO₂ (g_m), due, at least in part, to increased surface area of chloroplasts exposed to the intercellular airspace. The higher mesophyll diffusion conductance compensates for the reduction in stomatal conductance, resulting in overall higher WUE [23]. Upward arrows indicate higher values, and downwards indicate lower values. Figure obtained from Maron, 2019 [61].