Conditions
Energy partition [W m-2]
Leaf vs air temperature
The two vapour pressure deficits
Every number on this page came from an API call
This page ships no model code. Move a slider and it POSTs to
/leaf/steady; the charts come from /leaf/sweep.
The physics runs on Cloudflare, close to you, and the model itself never
leaves the server.
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What you may send
Read live from GET /leaf/schema — this table cannot drift from the deployed engine.
What this demo key can do
The key in this page is public by construction — you can read it in the page source. It is deliberately limited, and the API tells you its own ceiling:
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What this model computes
One leaf, in a greenhouse, in equilibrium with its own microclimate. Give it weather and a root zone; it returns the leaf's temperature, how fast it is losing water, how much tension that puts the water column under, and how long it can hold that state before something is damaged.
The reason it exists: the driving force for transpiration is not the vapour pressure deficit of the air. It is the deficit between the saturated air inside the leaf — at leaf temperature — and the air immediately around it. When a leaf in sun sits 6 K above air, those two numbers differ by a factor of two or more. Climate computers report the first. Plants respond to the second. The gap is the whole point — watch the two VPD lines separate as you raise the radiation slider.
Two switches that dominate
The cover. Longwave transmissivity — glass 0.02, bare PE 0.65, a closed screen 0.05 — decides the entire night balance. It is the largest single lever in the model, and it changes the daytime light too.
The air node. The leaf heats and humidifies the air it sits in. Pin that air to the bulk greenhouse air and you have the Penman-Monteith assumption; in still air the difference is several kelvin.
Honest limits
Photosynthesis here is a placeholder — structurally sound, not a carbon model. The canopy geometry is not calibrated: view factors describe an isolated leaf while the air node describes a canopy, so the night result under glass is softer than reality. Substrate retention curves are generic. This is a physics demonstrator, not a production advisory tool.