Even without nervous system, plants are sensitive to their environment and are able to change their metabolism to adapt themself to outdoor conditions. This imperceptible physiological transformation process can be measured using a GSR (Galvanic Skin Response) sensor. GSR is able to analyze changes in the epidermal conductance of the plant.
Then, the results of these analyzes are translated into MIDI language (communication protocol specific to electronic music) thanks Arduino uno and transmitted to an open source and virtual synthesizer made with PureData.
Arduino is connected to an USB to MIDI inferface wich is connected to a Raspberry Pi. Softwares run under Raspian Jessy.
Hardware and code is inspired by MIDI Sprout, a very well documented project :https://www.midisprout.com/