Summary:

Plant Water Demand

Plant water demand is influenced by stomatal conductance, which is described in the previous section. The model for plant water demand includes transpiration that is attenuated by a transpiration loss function based on leaf water potential.

Sunlit and Shaded Leaf Transpiration
- Sunlit leaf transpiration (E_sun) is calculated as the maximum sunlit leaf transpiration (E_sun,max) multiplied by a sigmoidal loss function based on sunlit leaf water potential (ψ_sunleaf).
- Shaded leaf transpiration (E_shade) is calculated similarly using shaded leaf water potential (ψ_shadeleaf).

Water Stress
- Sunlit transpiration water stress (β_t,sun) is calculated as the ratio of sunlit stomatal conductance (g_s,sun) to maximum sunlit stomatal conductance (g_s,sun,β_t=1).
- Shaded transpiration water stress (β_t,shade) is calculated similarly using shaded stomatal conductance.
- Water stress is used to attenuate photosynthesis, as described in the previous section.

The key equations provided describe the calculation of sunlit and shaded leaf transpiration, and the associated water stress factors, which are important components of the plant water demand model.