A plant physiological approach to reduce greenhouse energy consumption
The economic and environmental pressures associated with greenhouse heating for warm-season vegetable transplant production have prompted a search for biologically driven, cost-effective alternatives. This study investigates the potential of exogenously applied salicylic acid (SA), a phenolic phytohormone known for its stress-mitigating properties, to reduce energy consumption by enhancing seedling cold tolerance. Tomato seedlings (Solanum lycopersicum cv. Rutgers) were subjected to three concentrations of foliar-applied SA (0, 75, and 150 mg/L) and grown under two temperature regimes 16°C and 25°C, in growth chambers. Transplant morphological parameters, including shoot and root biomass, stem thickness, leaf development, and root system architecture, were analyzed over a 49-day growth cycle. At 16°C, application of 75 mg/L SA significantly enhanced seedling vigor, with shoot fresh weight, stem diameter, and leaf area comparable to those grown at standard commercial conditions of 25°C without SA. SA-treated seedlings exhibited enhanced root biomass and surface area, indicating improved cold tolerance. Importantly, energy modeling indicated that reducing the heating setpoint from 25°C to 16°C could lower heating energy requirements by approximately 45%, a savings enabled by the physiological benefits of SA. These findings underscore the dual role of SA as both a growth regulator and an abiotic stress mitigator, suggesting that targeted SA application could transform transplant production by reducing reliance on costly supplemental heating. This represents a novel integration of plant physiological intervention into sustainable energy management practices in horticulture.