Plants have sensory receptors through which they sense and respond to environmental cues. This work focuses on correlating the electrical responses of living plants with variations in environmental conditions. A pair of sharp metal probes were attached to the stem of a bell pepper plant to monitor its time-domain voltage characteristics. The plant was subjected to heat and pressure stimuli, water stress, and humidity variations. For every 50-degree centigrade increment in leaf temperature, there was an up to 3-fold enhancement in the measured voltage. A burst of voltage spikes was also observed when the leaf was pressed with a finger. Spikes in the measured voltage were observed in less than 5 seconds after exposing the plant to heat/pressure stimulus. The voltage spiked at the beginning of the 7-day stress cycle for a water stressed plant but subsided after the first day. The electrical responses of the plant were also investigated under three different humidity levels. The measured signals were analyzed through Morlet, Gabor, Bump, Dubecheis, and Haar wavelets to identify the dominant frequency components for each stress condition. In addition, autocorrelation and cross correlation values were computed to analyze the similarity between the measured time-series signals. The knowledge gained from this project will help engineering plants that are hypersensitive to environmental cues. These super-sensitive plants can be used as an early warning system in the event of a wildfire, toxic gas leakage, water/nutrient shortage, or pest attack. Our findings support that probing the electrical responses of plants will enable local climate monitoring and allow the growers to intervene immediately to reduce crop losses resulting from environmental stresses.
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