Leaf stomatal efficiency

Input: gs_val (candidate stomatal conductance)
                    │
                    ▼
    ┌──────────────────────────────────────┐
    │  Compute boundary layer conductances │
    └──────────────────────────────────────┘
                    │
          ┌─────────┴─────────┐
          ▼                   ▼
At gs = gs_val − delta    At gs = gs_val
   ┌───────────────┐    ┌───────────────┐
   │ Leaf temp     │    │ Leaf temp     │
   │ Photosynthesis│    │ Photosynthesis│
   │ → an2         │    │ → an1         │
   └───────────────┘    └───────────────┘
          │                   │
          └─────────┬─────────┘
                    ▼
    ┌───────────────────────────────────────┐
    │  CHECK 1: Efficiency                  │
    │wue = (an1 − an2) − delta·iota·(VPD/P) │
    │                                       │
    │  Marginal carbon  vs  Marginal water  │
    │  gain                    cost         │
    │                                       │
    │       wue > 0 → "still worth it"      │
    │       wue < 0 → "too expensive"       │
    └───────────────────────────────────────┘
                    │
                    ▼
    ┌──────────────────────────────────────┐
    │  CHECK 2: Cavitation safety          │
    │  leafwp = leaf_water_potential()     │
    │  minpsi = leafwp − ψ_min             │
    │                                      │
    │  minpsi > 0 → "No cavitation risk"   │
    │  minpsi < 0 → "danger of cavitation" │
    └──────────────────────────────────────┘
                    │
                    ▼
    ┌──────────────────────────────────────┐
    │  val = min(wue, minpsi)              │
    │                                      │
    │  val > 0 → open stomata more         │
    │  val < 0 → close stomata             │
    │  val = 0 → OPTIMAL gs (root)         │
    └──────────────────────────────────────┘
                    │
                    ▼
          Return val to Brent's method

---

source

leaf_stomatal_efficiency

def leaf_stomatal_efficiency(
    physcon:PhysCon, atmos:Atmos, leaf:Leaf, flux:Flux, gs_val:float
)->tuple:

Stomatal water-use efficiency check and cavitation check to determine maximum gs.

For the stomatal conductance gs_val, calculate photosynthesis and leaf water potential for an increase in stomatal conductance equal to “delta”.

The returned value is positive if this increase produces a change in photosynthesis > iotavpddelta or if the leaf water potential is > minl_wp.

The returned value is negative if the increase produces a change in photosynthesis < iotavpddelta or if the leaf water potential is < minl_wp.

Example leaf_stomatal_efficiency()