MINI-PAM-II/POROMETER

What is a 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 leaf surfaces that regulate gas exchange between the plant and the atmosphere. When stomata open, the leaf loses water through evaporation and takes up CO₂ for photosynthesis. When they close — due to drought, heat, or other stress — water loss decreases but photosynthesis slows down. Measuring stomatal conductance with a porometer therefore provides direct insight into how a plant responds to its environment. It is one of the most widely used parameters in plant stress physiology, irrigation management, and crop science.

 
Why Combine Porometry with Chlorophyll Fluorescence?
Conventional porometers measure only stomatal conductance — they tell you whether stomata are open or closed, but not how well the photosynthetic machinery is functioning. The MINI-PAM-II/POROMETER is the only instrument that adds full PAM chlorophyll fluorescence analysis to every porometry measurement. This means you get both sides of the equation simultaneously: how much gas exchange the leaf allows (stomatal conductance) and how efficiently it uses the light it absorbs (PS II quantum yield). This combination is particularly powerful for distinguishing between stomatal and non-stomatal limitations of photosynthesis - a question that is central to drought physiology, breeding for water use efficiency, and understanding plant responses to environmental stress.

How Does It Work?
The MINI-PAM-II/POROMETER is a specialized leaf clip that attaches to the MINI-PAM-II portable fluorometer. The clip encloses a 1 cm diameter sample area and contains integrated 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 calculates stomatal conductance and evaporation from the change in humidity caused by the enclosed leaf. Simultaneously, the PAM fluorometry system measures chlorophyll fluorescence parameters through the fiber optic. The entire measurement typically completes in under 15 seconds.

Fast and Reliable Porometry
The porometer delivers data every second. At a standard flow rate of 100 µmol s⁻¹ and typical stomatal conductance of 100 mmol m⁻² s⁻¹, a measurement completes in under 15 seconds. An automatic stability determination ensures reliable results — simply clip the leaf, wait for the stability criteria, and the measurement executes automatically with an optional acoustic signal.

Works on Leaves and Needles
The 1 cm diameter measuring chamber accommodates broadleaves as well as conifer needles — a significant advantage over porometers with larger chambers that struggle with narrow samples. The removable dark shield enables F_V/F_M measurements with controlled actinic light for dark-acclimated samples.

Comprehensive Sensor Suite
Every measurement automatically includes data from built-in GPS, accelerometer, gyroscope, and magnetoscope — providing geospatial coordinates, sun angle, and leaf angle with every data point. A cosine-corrected PAR sensor at the sample level and a leaf temperature thermocouple complete the environmental context. No other porometer provides this level of environmental metadata.

Established Measurement Protocols
Beyond rapid single-point porometry, the system supports advanced protocols including induction curves and light curves. These enable detailed analysis of stomatal dynamics over time — for example, tracking stomatal opening and closing responses to light changes or drought onset.