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Development of a Low-Cost, Autonomous Pulse Amplitude Modulated (PAM) Chlorophyll Fluorometer for In-Situ Monitoring of Photosystem II Efficiency

Samaneh Baghbani, Uygar Akkoc, Clara Stock, Christiane Werner, Stefan J. Rupitsch

TL;DR

This work addresses the need for autonomous, low‑cost in situ monitoring of PSII efficiency by developing a compact PAM fluorometer (~€150, 50 g) that uses a single LED to deliver measuring light and saturation pulses and transmits $F$, $F_m'$, and $\Phi_{PSII}$ via LoRa. The device achieves performance comparable to commercial instruments ($R^2 = 0.95$) across three plant species and a range of light conditions, validated against a Micro‑PAM in a controlled climate chamber. Reproducibility tests on 20 units show stable measurements (SD $<0.03$ across PAR after addressing high‑light saturation issues), supporting large‑scale deployment for fine‑scale forest canopy monitoring. The approach enables scalable, deployable, wireless monitoring of photosynthetic efficiency in natural ecosystems with potential improvements in flexibility and energy autonomy for field use.

Abstract

The quantum yield efficiency of photosystem II (PhiPSII) is an important parameter for assessing the photosynthetic performance and stress status of plants. Commercial PAM fluorometers can measure this parameter, but they are often expensive, bulky, or lack autonomous operation. This work presents the development of an autonomous PAM fluorometer designed to address these limitations and enable large-scale deployment. It supports high spatio-temporal monitoring of PhiPSII in forest canopies under a wide range of ambient light conditions. The prototype costs approximately 150 EUR, has dimensions of 3 cm x 6 cm x 2 cm, and weighs about 50 g. In side-by-side tests across three plant species, it achieved measurement accuracy comparable to state-of-the-art commercial sensors, with a correlation factor of R^2 = 0.95.

Development of a Low-Cost, Autonomous Pulse Amplitude Modulated (PAM) Chlorophyll Fluorometer for In-Situ Monitoring of Photosystem II Efficiency

TL;DR

This work addresses the need for autonomous, low‑cost in situ monitoring of PSII efficiency by developing a compact PAM fluorometer (~€150, 50 g) that uses a single LED to deliver measuring light and saturation pulses and transmits , , and via LoRa. The device achieves performance comparable to commercial instruments () across three plant species and a range of light conditions, validated against a Micro‑PAM in a controlled climate chamber. Reproducibility tests on 20 units show stable measurements (SD across PAR after addressing high‑light saturation issues), supporting large‑scale deployment for fine‑scale forest canopy monitoring. The approach enables scalable, deployable, wireless monitoring of photosynthetic efficiency in natural ecosystems with potential improvements in flexibility and energy autonomy for field use.

Abstract

The quantum yield efficiency of photosystem II (PhiPSII) is an important parameter for assessing the photosynthetic performance and stress status of plants. Commercial PAM fluorometers can measure this parameter, but they are often expensive, bulky, or lack autonomous operation. This work presents the development of an autonomous PAM fluorometer designed to address these limitations and enable large-scale deployment. It supports high spatio-temporal monitoring of PhiPSII in forest canopies under a wide range of ambient light conditions. The prototype costs approximately 150 EUR, has dimensions of 3 cm x 6 cm x 2 cm, and weighs about 50 g. In side-by-side tests across three plant species, it achieved measurement accuracy comparable to state-of-the-art commercial sensors, with a correlation factor of R^2 = 0.95.

Paper Structure

This paper contains 17 sections, 2 equations, 11 figures, 1 table.

Table of Contents

  1. Introduction
  2. Materials and Methods
  3. Principle of PAM Fluorometry and Saturation Pulse
  4. Sensor Design and Architecture
  5. Sensor Head
  6. Fluorescence Excitation
  7. Fluorescence detection
  8. Data Acquisition and Transmission
  9. Sensor Cost Analysis
  10. Sensor Housing
  11. Sensor Characterization and Validation
  12. Side-by-Side Measurements with a Commercial PAM Fluorometer
  13. Reproducibility and Calibration
  14. Results and Discussion
  15. Results of Side-by-Side Measurements with the Commercial Device
  16. ...and 2 more sections

Figures (11)

  • Figure 1: Principle of PAM fluorometry within dark-light transition. The measuring light pulses are used to probe the photosynthetic activity of the leaf.
  • Figure 2: Steady state fluorescence and maximum fluorescence in dark and light conditions.
  • Figure 3: Block diagram of the sensor system.
  • Figure 4: Light absorption and emission by chlorophyll a molecules.
  • Figure 5: Measurement protocol for the measuring light and saturation pulse.
  • ...and 6 more figures