Plant Stress Snapshot

A one-moment health check for a plant. You enter a few readings — canopy greenness (NDVI), the leaf's temperature, the surrounding air temperature, and optionally a sap-flow sensor value — and it combines them into vitality and stress scores. The key idea is "canopy temperature depression": a well-watered plant cools itself by transpiring, so its leaves sit slightly BELOW air temperature; when the leaf runs hotter than the air, the plant has likely closed its stomata and is water-stressed.

For a quick spot-check on a specific plant or block when you suspect stress — wilting, a hot afternoon, an irrigation hiccup — and you have a cheap infrared thermometer. Works for any crop with an open canopy. It is a single manual snapshot, so it is a diagnostic prompt, not continuous monitoring; take a few readings across the room rather than trusting one plant.

Vitality Index near 100 is good; it drops as water or heat stress climbs. The Leaf-Air Temp Diff is the tell: a small negative or near-zero number is healthy (leaf cooler than air = transpiring freely), while a positive number (leaf hotter than air) drives the Water Stress Index up and means irrigate or check root-zone problems. A high Heat Stress Index (leaf above ~85°F) calls for cooling or shade. Because the coefficients are heuristic, act on the direction — go water or cool — rather than the exact percentage.