Plants possess sensing mechanisms which are employed to monitor the environment for optimal growth. This sensing mechanism can be observed by the change in behavior in plants like Mimosa pudica (touch me not) which closes its leaves when touched or Dionaea muscipula (Venus flytrap) which closes its trap when an insect gets in it. It has been established that plants produce an electrical signal response to stimuli which is used to control various physiological phenomena within the plant. These electrical signals, which may have embedded signatures capturing the essence of the stimuli affecting them, may be used as means of sensing the environment in which they grow.

Excitability in plants occurs due to the high sensitivity of protoplasm and all cell organelles to any natural and electrochemical effects. It is reported that due to any type of stimulus, an initial influx of Ca²⁺ triggers a Cl^- efflux via anion channels which lead to massive and quick plasma membrane depolarization. A slow repolarization of the plasma membrane takes place due to activation of K⁺ efflux up to the resting potential. Due to ion channel gating, this electrical wave (due to influx and efflux of ions) propagate through the sieve tubes.

 Apart from a local electrical potential (LEP), which is induced and sustained due to a wounding/injury and stops a few millimeters from a dying cell, there are action potential (AP) and variation potential (VP). All these three types of signals are due to a transient change in the membrane potential of plant cells (depolarization / repolarization phases), but only VP’s and AP’s make use of the vascular bundles to systemically spread through the entire plant body. Out of these three types of electrical signals, AP and VP are of particular interest and several works have been reported in analyzing them including mathematical modeling of such signals.  

Plants, covering around one third of earth’s land mass in the form of forests, are found in abundance, thereby covering a large geographical area naturally. Plants are also affected by the same parameters (environmental pollutants) as other living beings sharing the same natural environment. Therefore, if electrical signals such as AP / VP / SP from each plant could be used to monitor a certain area around that particular plant, then their abundantly distributed presence could be used to monitor a larger area at the same time. The viability of such an approach seems immense, but several questions rise along with this. If such electrical signals are extracted and analyzed, information about the external stimuli which caused the electrical signal may be found. A successful analysis of such signals will assist the idea of plants being used as a living, multiple stimuli biosensor.