Towards Tomato Plant Iron Stress Monitoring Through Bioimpedance and Circuit Analysis

Insufficient availability of essential nutrients, such as iron, can impede plant growth, decrease crop productivity, and even lead to mortality. This is why it is crucial to detect early signs of stress and prevent yield loss, via proximal monitoring techniques. In this study, stem impedance of 8 tomato plants was measured each 1 hour to monitor the impact of iron stress. The normalized impedance magnitude at 10 kHz was continuously measured over 38 days. The results reveal a noticeable divergence in the trend of impedance magnitude shortly after the elimination of iron from the nutrient solution, indicating the effect of iron stress on plant bioimpedance. Additionally, the Cole model was employed to evaluate the electrical parameters of the impedance spectra. The fitting results exhibited an average root mean square error of 466.3 Ω. Statistical analysis of the extracted circuit parameters revealed significant differences between iron-stressed and control plants, highlighting their potential as relevant features for discriminating plant health conditions. Our findings highlight the usefulness of impedance measurements for monitoring iron stress in plants and provide insights into the physiological responses of tomato plants to nutrient deprivation.