Hydroponic Thermal Regulation for Low-Energy Winter Strawberry Production in Mediterranean Coastal Infrastructures

The implementation of immersion heaters in hydroponic strawberry systems offers substantial potential for reducing glasshouse operational costs. This 115-day study investigated the effects of nutrient solution temperature on strawberry physiological and biochemical parameters. Temperature significantly influenced anthocyanin accumulation, with a maximum increase (135.49%) at 20 °C. Total chlorophyll content and photosystem II efficiency (Fv/Fm) exhibited temperature-dependent variations, while the 20 °C treatment served as the optimal baseline. Plants maintained at 20 °C demonstrated superior growth performance, achieving 64.79% higher fresh shoot weight and 50.29% greater total dry biomass compared to controls. Fruit quality parameters remained largely temperature-independent, except at 15 °C, which produced fruits with elevated sugar content but reduced acidity and dimensions. Conversely, the 20 °C treatment yielded the maximum fruit weight. Photosynthetic rates peaked during the experimental period, with plants at 20 °C exhibiting optimal recovery capacity. Both transpiration and stomatal conductance displayed treatment-specific patterns, with 20 °C maintaining superior physiological responses despite stress periods. These findings establish that maintaining nutrient solution temperature at 20 °C optimizes strawberry physiology, growth, and fruit quality, validating temperature regulation as an effective practice for hydroponic strawberry production systems.