POROMETER

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.

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.

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:

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.

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.

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.