Development of an advanced embedded system for description of electrophysiological phenomena in ornamental plants by biosignals processing

Extracellular electrical signals that are produced from plants have different patterns depending on factors that may cause stress such as water deficiency, nutrient shortages, high salinity level in the root environment etc. In practice, growers and greenhouse control systems acts against the stress factor when visible symptoms are observed, or when the measured values of parameters related to the stress are outside certain limits during a pre-defined period. However, the decrease in plant growth has already begun during this period with consequences for production. The objective of this work is the development of an advanced embedded wireless sensor to detect electrophysiological phenomena in order to investigate the correlation of biosignal patterns to salinity stress in ornamental plants. This embedded system could be used to improve the efficiency of irrigation control systems especially in soilless cultures. For this reason an integrated embedded hardware was designed for plant biosignal measurements. In order to avoid white Gaussian noise (WGN caused from 50 Hz power line noise as well as the noise of the electrical devices operating inside the greenhouse), the IEEE 802.15.4 protocol was used for wireless communication to the embedded systems. Electrical potential difference in leaves of single stem Chrysanthemum (Chrysanthemum moriflorum) plants grown in soilless culture and irrigated with low and high electrical conductivity (EC) nutrient solution were measured using the embedded wireless system and a traditional wire data acquisition system (DAQ). The measurements are recorded for a period of 4 days, via a data acquisition system and processed using LabVIEW code. The results show that biosignal measurements on plants, obtained with the use of the design wireless embedded system have a negligible error in contrast to wired data acquisition, since these are not affected by RF and other similar signal noise. The experimental measurements showed that there is a significant correlation between the mean
voltage value of the measured biosignal (V )and the EC level of the substrate where the plants were grown.