POROMETER

A porometer measures how easily water vapour passes through the stomata of a leaf - a parameter known as stomatal conductance. Stomata are the small pores on the leaf surface that regulate gas exchange between the plant and the atmosphere. When stomata open, the leaf loses water through transpiration and takes up CO₂ for photosynthesis; when they close - under drought, heat, or other stress - water loss drops but photosynthesis slows. Measuring stomatal conductance with a leaf porometer therefore gives direct insight into how a plant responds to its environment, making it one of the most widely used parameters in plant stress physiology, irrigation management, phenotyping, and crop science.

Conventional porometers measure stomatal conductance alone - they tell you whether stomata are open or closed, but not how well the photosynthetic machinery is performing. Our porometer is the only porometer/fluorometer that adds full PAM chlorophyll fluorescence analysis to every porometry measurement. You capture both sides of the equation at once: how much gas exchange the leaf allows (stomatal conductance) and how efficiently it uses absorbed light (PS II quantum yield). Because the system uses complete pulse-amplitude-modulated (PAM) fluorometry with saturating pulses - not just single-turnover fluorescence - it resolves the full quenching analysis. This is decisive for separating stomatal from non-stomatal limitations of photosynthesis, a central question in drought physiology, breeding for water use efficiency, and the study of plant stress responses.

The MINI-PAM-II/POROMETER is a specialized leaf clip that attaches to the MINI-PAM-II portable chlorophyll fluorometer. The clip encloses a 1 cm diameter sample area and integrates humidity sensors, a leaf-temperature sensor, and a fiber-optic port for PAM fluorescence excitation and detection. During a measurement, a defined airflow passes through the chamber; the porometer derives stomatal conductance and transpiration from the humidity change caused by the enclosed leaf, while the PAM system simultaneously records chlorophyll fluorescence through the fiber optic. The entire measurement typically completes in under 15 seconds.

The porometer delivers data every second. At a standard flow rate of 100 µmol s⁻¹ and a typical stomatal conductance of 100 mmol m⁻² s⁻¹, a measurement finishes in under 15 seconds. Automatic stability detection keeps results reliable - clip the leaf, wait for the stability criteria, and the measurement runs automatically with an optional acoustic signal. This makes the system ideal for rapid field screening of large sample sets.

The 1 cm diameter measuring chamber accommodates broadleaves as well as grasses and conifer needles — a significant advantage over other commercially available porometers that struggle with narrow samples. The removable dark shield enables F_V/F_M measurements with controlled actinic light for dark-acclimated samples.

Every measurement automatically logs data from a built-in GPS, accelerometer, gyroscope, and magnetometer - providing geospatial coordinates, sun angle, and leaf angle with every data point. A cosine-corrected PAR sensor at sample level and a leaf-temperature thermocouple complete the environmental context. No other handheld porometer captures this depth of environmental metadata.

Beyond rapid single-point porometry, the system supports advanced protocols including induction curves and light curves, enabling detailed analysis of stomatal dynamics over time for example, tracking stomatal opening and closing in response to light transitions or drought onset.