Effects of Water Deficit and GABA-Containing Biostimulant on Maize Plants: Nondestructive Monitoring by X‑Ray...

Climate change increases the frequency of water deficit in crops, requiring efficient mitigation and monitoring strategies. This study evaluated the use of portable X-ray fluorescence (pXRF) and visible spectroscopy (400-700 nm), combined with principal component analysis (PCA), to rapidly detect water stress in maize (Zea mays L.), and assessed the protective effect of a foliar biostimulant containing GABA (GCB). Water deficit reduced stomatal conductance, chlorophyll content, and plant growth, while increasing membrane damage and leaf temperature. GCB, especially at 30 g ha^-1, mitigated stress effects by improving physiological stability, preserving photosynthetic pigments, and enhancing biomass and leaf area. PCA effectively discriminated treatments, with 670-690 nm (chlorophyll) and 490-600 nm (carotenoids) identified as key spectral regions, while pXRF signals for K and Ca reflected stress-induced changes. The integration of biostimulants with portable spectroscopy represents a promising nondestructive approach for monitoring and managing water stress in maize under climate-related constraints.