MINI-PAM-II

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Portable PAM Fluorometer for Field and Laboratory

The Standard for PAM Fluorometry in Field Research

The MINI-PAM-II is a portable chlorophyll fluorometer based on the pulse-amplitude modulation (PAM) technique. It enables rapid, non-destructive assessment of photosystem II efficiency, electron transport rate, and plant stress responses directly at the site of interest. Energy-efficient LED sources and easy-to-replace batteries ensure extensive measurements in remote locations. Sensitivity, small dimensions, reliability under rugged conditions, and simple execution of fluorescence analysis make the MINI-PAM-II the standard for PAM fluorometry.

What is Chlorophyll a fluorescence?

When chlorophyll molecules absorb light during photosynthesis, a small fraction of that energy is re-emitted as fluorescence. Measuring this chlorophyll fluorescence signal provides a direct, non-invasive window into the photosynthetic performance of the plant without causing any damage. Chlorophyll fluorescence analysis is a well-established technique for detecting and quantifying environmental stress, photoinhibition, nutrient deficiency and acclimation processes in plants, algae, lichens and cyanobacteria. As the measurements are non-invasive, the same leaf or organism can be monitored repeatedly over time.

The MINI-PAM-II uses the pulse-amplitude modulation (PAM) technique - a technique that enables the detection of weak chlorophyll fluorescence signals even in full sunlight. The key principle is that the instrument emits rapidly pulsed measuring light at a defined modulation frequency. As the detector only responds to signals at this exact frequency, it can clearly distinguish the fluorescence emitted by the plant from the much stronger unmodulated ambient light. This separation allows reliable measurements to be taken in the field without the need to shield the leaf.

From these measurements the system automatically calculates many different parameters, namely F_V/F_M (maximum photochemical yield), Y(II) (effective photochemical yield) and its complementary yields Y(NPQ) and Y(NO), as well as parameters of photochemical (qL, qP) and non-photochemical quenching (NPQ, qN).

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Ready for Fieldwork

Energy-efficient LED sources, storage capacity for 27,000 data sets, and easy replaceable off-the-shelf batteries permit extensive measurements in remote places. A sun-readable touchscreen serves as easy-to-use interface for field studies. The fluorometer automatically calculates and displays all relevant parameters of saturation pulse analysis.

The far-red light (735 nm LED) of the MINI-PAM-II preferably excites photosystem I. Low intensity far-red light induces nearly no charge separations in photosystem II. A special measuring routine uses this far-red light to determine the F₀’ fluorescence level, which is important to correctly assess the redox state of photosystem II reaction centers.

Blue and Red Version

The MINI-PAM-II is available in a blue version (470 nm) and a red version (655 nm), optimized for different sample types. Blue excitation is standard for higher plants and green algae, while red excitation is preferred for cyanobacteria and samples where blue-light-induced responses should be avoided.

Versatile Accessories: Expanding Your Research

The MINI-PAM-II grows with your research. A wide range of accessories adapts the system to virtually any application. From leaf clips and miniature spectrometer to porometer, suspension cuvette with oxygen sensor, multi-color lamp, and barcode scanner.

The POROMETER leaf-clip enables combined measurements of stomatal conductance and chlorophyll fluorescence, making it ideal for rapid stress screenings, field studies, and detailed plant analysis - all within a compact, GPS-equipped device. It is the only porometer on the market that combines porometry with full PAM chlorophyll fluorescence analysis, thereby suitable for broad leaves, grass blades and needles.

For suspension-based work, the Suspension version of the MINI-PAM-II using the KS-2500 cuvette paired with the MKS-2500 stirring unit allows simultaneous chlorophyll fluorescence and oxygen measurements in just 400 µl of sample, with optional temperature control via a connected water bath.

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Measuring simultaneously PAM fluorescence, PAR, leaf temperature and relative humidity

The MINI-PAM-II combined with the digital leaf clip 2035-B measures simultaneously PAM fluorescence, photosynthetically active radiation (PAR), leaf temperature and air humidity.
The present experiment demonstrates how these parameters vary during a partly cloudy spring day. The photosynthetic sample was an attached leaf of Ilex aquifolia growing the garden of the Walz Company.

Effective quantum yield of photosystem II (Y(II)) of an attached holly leaf (Ilex aquifolium) and photosynthetically active radiation (PAR) during a partly cloudy spring day. During the first half of the day, PAR increased occasionally to values around 500 μmol m^-2s^-1 and the Y(II) varied in an opposite manner to PAR.

Simultaneous Recording of Fluorescence and Oxygen

Fluorescence measurements were carried out with a MINI-PAM/B fluorometer to which an FSO2-1 system (optode plus oxygen meter) was connected via an FSO2-AK interface. The sample in a KS-2500 cuvette was stirred by a MKS-2500 stirrer. Both, the fluorometer’s fiberoptics and the optode were connected to the suspension cuvette.

The light regime consisted of 5 min illumination periods alternating with 5 min of darkness: the PAR increased from the first to the last illumination interval (Fig. 1). Saturation pulse analysis was performed at the end of dark and light periods.
The slopes of light-driven oxygen increases were similar for all light intensities (Fig. 1 and 2). In comparison, the photosystem II yield Y(II) at the end of light periods decreased with light intensity (Fig. 1). The discrepancy can possibly be explained by the fact that Y(II) is related to the Q_A redox state, whereas the oxygen signal is related to the turnover of Q_A.

Figure 1: Simultaneous measurement of fluorescence and oxygen of a suspension of Synechococcus leopoliensis (Cyanobacteria). The screenshot shows time courses of oxygen concentration (blue line), continuous PAM fluorescence (black line), PAR (yellow line), and Y(II) (green line). The PAR was 6, 13, 19, 27, 38, 56, 85, 125, 187, 245, 344, 450 μmol m^-2 s^-1. Y axis scaling is percentage of oxygen saturation.

The MINI-PAM-II/POROMETER provides information on e.g. evaporation rate, VPD and stomatal conductance of the measured leaves. Measurements are easy to perform and provide accurate results within a typical sample measurement time of 15-30 seconds. To show typical measuring sequence, the datapoints were recorded every second using the WinControl-3 software. The dot circled in red marks a manual measurement triggering an additional saturation pulse analysis.

To optimize the workflow, the stability assessment can be performed automatically by the device. The change in conductance is then evaluated and the measurement is automatically triggered as soon as the stability criteria are met. The stability criteria are preset but can be customized to suit the individual requirements. The stability criteria can be applied to both types of data acquisition: either porometer data only or the combination of SAT pulse analysis and porometer data acquisition. The latter was used for the analysis on shaded-grown (A) vs. sun-exposed (B) Viburnum rhytidophyllum leaves.

WinControl-3 screenshot showing porometer data recording with stomatal conductance stabilization over time

These differently grown leaves show many differences in parameter of porometer and chlorophyll fluorescence analysis. The figure shows as an example the results of stomatal conductance (gs) and Y(II). Particularly interesting for field measurements: the Porometer logs GPS, leaf solid angle of the surface normal and the incident vector of sunlight with each dataset so that the sample´s geographical context can be documented precisely.

MINI-PAM-II/POROMETER field measurements showing stomatal conductance and Y(II) results for shade-grown and sun-exposed leaves

Comparison of stomatal conductance and PSII yield between shade-grown and sun-exposed Viburnum leaves measured with MINI-PAM-II/POROMETER

The MINI-PAM-II/POROMETER offers even more. This porometer allows MINI-PAM-II protocols to be combined with porometer data, adding an important aspect of gas exchange to these established tools for chlorophyll fluorescence analysis. This facilitates the measurement of evaporation, VPD, stomatal conductance and stomatal movement e.g. during light curves or induction curves. The figure shows stomal movement during an induction curve measured on a Taraxacum leaf.

The MINI-PAM-II/POROMETER can be operated with both MINI-PAM-II versions. Depending on the version, the actinic illumination is provided with red or blue actinic light. If you prefer a more flexible choice of light colors, you can use the External LED Source 2054-L for the actinic lighting with red, green, blue or white light, or mixtures of these four light qualities like it was done in this experiment:

This is a screenshot of Taraxacum two-step induction curve with 10% blue, 10% green 10% red and 70% white at 190 µmol m^-2 s^-1, then 380 µmol m^-2 s^-1. Showing mainly the first part of this two-stage induction curve indicating Y(II) (green), PAR (yellow), ETR (red), NPQ (light blue) and stomatal conductance (dark blue). The Y-axis scaling refers to the stomatal conductance in mmol m^-2 s^-1.

A new clock feature the "Yield + Poro Only" gives the ability to trigger a saturation pulse, followed by a sequence of porometer-only measurements. This clock item is ideal for monitoring purposes if you want detailed information about stomatal conductance but less frequent saturation pulse measurements. In stand-alone operation, just supplied with some extra power, the MINI-PAM-II with porometer can monitor your sample for several days. You can capture PS(II) photosynthesis and the dynamics of stomata and their adaptation to changing conditions in a detailed and continuous manner as you can see here in two monitoring experiments:

1. Diurnal and Nocturnal monitoring of a Kalanchoe laxiflora leaf:

The plant was cultivated under a 12-hour light (680 µmol m⁻² s⁻¹) and 12-hour dark cycle. As is typical for CAM plants, the porometer determines stomatal opening at night. As long as the plant was adequately watered, stomatal opening also occurred during the second half of the day e.g. to maintain photosynthetic efficiency. Initially well-watered, the data clearly show a decline in stomatal aperture during the second half of the day over the first three days. Following irrigation on the fourth day, there is a marked increase in nocturnal stomatal opening compared to the previous three nights.

2. Six-day monitoring experiment of a tomato leaf grown a small glasshouse

In this experiment the instrument executed porometer and chlorophyll fluorescence measurements every half hour for monitoring a tomato leaf continuously for six days inside a small greenhouse. The figure displays some of the comprehensive data collected during this period. Daily cycles were well measured, and you can see the performance of the leaf under the fluctuating light conditions throughout the day.

The MINI-PAM-II/POROMETER allows for the simultaneous recording of environmental parameters, such as the CO₂ concentration within the greenhouse. Shown in grey is the CO2 concentration inside the greenhouse. It exhibits significant fluctuations with peak concentrations of more than 750 ppm CO2 during the day.

In accordance with M.A.Caird et al. (Funct Plant Biol. 2007 Apr;34(3):172-177. doi: 10.1071/FP06264) the tomato leaf measured in this experiment did not fully close the stomata and showed significant transpirational water loss throughout the night.

Experience precision and flexibility research with the MINI-PAM-II/Porometer.