Figure 3.
Relationships that influence the optimal value of μw (∂A/∂E, the marginal carbon revenue of transpiring water—the increase in leaf carbon gain that would result from an infinitesimal increase in water loss). Changes in stomatal conductance and therefore water loss lead to immediate carbon gains (in photosynthesis) and costs (of repairing xylem embolisms resulting from reduced water potential), which directly affect ∂A/∂E. However, optimal carbon partitioning requires coordination between ∂A/∂E and the marginal carbon cost of acquiring water. Optimality‐based prediction of ∂A/∂E and thus, stomatal conductance, should consider these long‐term, amortized costs as well as the direct, immediate costs and benefits of variations in stomatal conductance.