This thesis investigates the possibility of detecting electrical changes in plants as an indicator of
plant state during water deficiency. The original plan focused on monitoring plant electrical
signals during gradual drying of the substrate. During the work, the experimental part was
redirected toward verification of the measurement chain, comparison of electrode designs and
observation of selected responses to external stimuli.
The experimental plant was tomato, cultivar Novosadski jabucar, Solanum lycopersicum
‘Novosadski jabucar’. The measurement chain was based on an AD8232 module, an Arduino
Nano microcontroller and Python-based data acquisition and processing. The measurement chain
was verified with an Agilent 33220A function/arbitrary waveform generator and two resistive
dividers. The tests provided two input signals of different amplitudes and enabled an approximate
conversion of the recorded amplitude units to input voltage, about 4.52 µV per unit.
Three electrode designs were compared: inserted silver electrodes, wrapped silver electrodes and
spring-loaded gold contact electrodes. For plant measurements, a unified fourth-order low-pass
digital filter with a 30 Hz cutoff frequency was used. The results show that measurable changes
can be observed with the implemented setup, but also that the measurements are strongly affected
by electrode contact, electrode design and plant condition. Wrapped electrodes lost contact
during severe plant wilting, while inserted and spring-loaded contact electrodes maintained
contact more reliably.
The thesis does not prove a unique relationship between water deficiency and a specific plant
electrical signal. It presents a measurement approach, practical limitations and an electrode
comparison that can support further controlled measurements of plant electrical signals.
|
