Effect of Biostimulants on Physiological and Quality Aspects of Tomato under Drought Stress

Abstract

Drought stress represents a significant abiotic factor restricting the productivity of tomato (Solanum lycopersicum L.), especially in the context of changing climatic conditions. Recently, biostimulants have gained attention as a sustainable strategy to enhance plant tolerance by modulating stress mechanisms in plants. This study evaluated the potential of selected biostimulants—melatonin (100 µM), salicylic acid (1 mM), arbuscular mycorrhizal fungi (AMF), and plant growth-promoting rhizobacteria (PGPR) to enhance drought tolerance in two tomato varieties: Vellayani Vijai (tolerant) and Arka Vikas (susceptible). A pot experiment was conducted using a factorial completely randomized design with two varieties and five treatments including stress control. Drought was induced at the flowering stage by withholding irrigation till relative water content of leaves reached 70%, and physiological and quality attributes were assessed. Results showed significant improvements in all physiological and quality attributes upon biostimulant application in both the varieties. Melatonin treatment led to the highest chlorophyll stability index (82.63 %), photosynthetic rate (20.13 µmol CO2 m-2 sec-1), stomatal conductance (0.0193 mmol H2O m-2 sec-2) and specific leaf area (297.04 cm2 g-1). Quality attributes such as total soluble solids (7.10 °Brix) and shelf life (18.67 days) of tomato fruits were also significantly increased with biostimulants application. AMF and PGPR also contributed positively to the drought stress tolerance. These findings suggest that biostimulants serve as an effective and environmentally friendly means to enhance drought tolerance in tomato, providing a sustainable strategy to promote climate resilience.