Figure 1.

Schematic depiction of the three proposed adjustments necessary for plant productivity in a given environment: (i) photosynthetic capacity (light- and CO₂-saturated intrinsic capacity of photosynthesis determined by the level of photosynthetic proteins) to provide sugars (the plant’s source strength) fueling crop yield; (ii) high flux capacities for distributing water throughout the leaf as well as loading and exporting sugars from the leaf (foliar water-intake & sugar-export capacities; see Section 4.5 below); and (iii) sink activity (growth, reproduction, and storage; sink strength). Modified from Demmig-Adams et al. [7] and Adams et al. [10]. The left panel illustrates CO₂ uptake and water loss through leaf stomates, which requires sufficient water delivery to the leaf. The middle panel shows a leaf vein that contains conduits for water import (blue) into and conduits for sugar export (green) out of the leaf. The right panel shows examples of sugar-consuming and -storing sink tissues that constitute the plant’s demand for photosynthate.