Photosynthesis rate follows light-response and CO2-response curves that saturate at high intensity. Water moves upward via the cohesion-tension mechanism through xylem, driven by transpiration pulling water from roots to leaves through stomatal pores.
P = Pmax · (I / (I + K_I)) · (CO2 / (CO2 + K_C)) · W_factor
Transpiration ∝ stomatal conductance × (leaf-air vapor gradient)
Stomata openness ↑ with water availability, ↓ under drought stress
- Light intensity — drives the light-dependent reactions; particle flow (photon absorption) and leaf glow scale with it.
- CO2 level — substrate for carbon fixation in the Calvin cycle; raises photosynthesis rate up to a saturation point.
- Soil water — root uptake availability; low water closes stomata to conserve moisture, throttling gas exchange.
- Nutrient level — nitrogen/phosphorus availability that scales overall plant vigor and growth rate.
Understanding these curves underlies precision agriculture and greenhouse climate control, where growers tune light, CO2 enrichment, and irrigation to maximize crop yield.