Measuring Stomatal Conductance with FLIR Lepton Thermal Arrays
How non-invasive micro-radiometric thermal imaging detects stomatal transpiration shutdown 36 hours before visual symptoms appear in tropical houseplants.
Dr. Siddhant Tiwari
Head of Biophysics, Vriksh Vani Labs
The Physics of Stomatal Transpiration
Plants exchange water vapor and carbon dioxide through microscopic leaf pores called stomata. When a plant photosynthesizes under optimal atmospheric conditions, continuous evaporative cooling lowers the leaf surface temperature relative to ambient room air by 1.5°C to 3.2°C.
When root water uptake declines or vapor pressure deficit (VPD) rises above tolerable thresholds, guard cells lose turgor pressure, forcing stomata to seal tight to prevent desiccation. This stomatal closure halts evaporative cooling, causing the leaf surface temperature to immediately spike toward or above ambient room temperature.
Micro-Radiometric Thermal Arrays in NIH-01
Traditional soil moisture probes measure electrical conductivity in substrate surrounding roots, missing local root hair hypoxia, soil channeling, or VPD-induced transpiration stress. The FLIR Lepton 3.5 sensor array in NIH-01 measures true leaf surface radiant thermal energy at 80x60 thermal pixel resolution.
By sampling spatial thermal gradients across leaf laminae at 1-minute intervals, the NIH-01 edge processor detects minute thermal spikes (+0.4°C/hr) indicative of early transpiration shutdown—giving plant owners a 36-hour head start before physical leaf drooping or tip browning occurs.
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