Physiological and Spectral Responses of Centella asiatica (L.) to Drought Stress: Implications for Growth, Yield, Stress Monitoring, and Modeling

Centella asiatica (L.) is an important medicinal herb valued for its wound-healing, anti-inflammatory, and cognitive-enhancing properties. However, information on its physiological responses to drought stress and the application of hyperspectral remote sensing for drought assessment in this species remains limited. This study evaluated the effects of four soil moisture regimes (control, mild, moderate, and severe drought) on plant growth, physiology, and leaf spectral reflectance in two trials. Drought stress significantly reduced gas exchange, growth, and biomass production. Under severe drought, stomatal conductance decreased by 88%, accompanied by a 37% increase in canopy temperature. Net photosynthetic rate declined by 69% and was positively correlated with soil moisture content (R = 0.80). Marketable fresh weight declined from 6.5 under control to 1.0 kg m -2 under severe drought, while dry biomass decreased from 0.64 to 0.26 kg m -2 in trial 1 and from 0.57 to 0.28 kg m -2 in trial 2. Drought stress also altered leaf spectral reflectance, particularly in the visible region, resulting in significant changes in several vegetation indices that were strongly correlated with key morpho-physiological traits. Additionally, functional relationships between soil moisture and major physiological and growth traits were established through environmental productivity indices, providing a quantitative framework for predicting plant responses to water availability. These findings demonstrate the potential of hyperspectral sensing for early, non-destructive drought detection and provide practical tools for improving irrigation management and precision cultivation of C. asiatica under field and greenhouse conditions.