Exogenous application of hormones and chemicals to mitigate heat stress in strawberry under tropical summer conditions.

Resilience of Strawberries in tropical and subtropical climates, including Bangladesh, faces severe challenges due to rising summer temperatures and sporadic heatwaves exacerbated by climate change. The experiment evaluated the physiological and biochemical responses of three Strawberry genotypes of which G1 (RABI-3) was heat tolerant and G2 (BARI Strawberry-2) and G3 (BARI Strawberry-3) were heat susceptible and assessed the effectiveness of five exogenous substances like 5% Molasses (T1), 10 ppm Melatonin (T2), 5% Kaolin (T3), 10 mM CaCl2 (T4) and 5 ppm Abscisic acid (T5) in mitigating heat induced damage. The experiment was conducted in pots under field conditions following CRD (Completely Randomized Design) set was repeated thrice. Exogenous treatments were applied as foliar spray at five days intervals for three months in comparison to the control. The hourly temperature and relative humidity (%RH) data was recorded using digital data logger. Leaf fluorescence parameters, temperature differentials, photosystem II efficiency and leaf attributes such as thickness and greenness were analyzed. The plant data was recorded three time viz. at the end of March, at the end of April and at the end of May using a handheld fluorometer (Multispeq V.02). The result showed that the heat tolerant genotype (G1) consistently maintained higher photosynthetic activity and chlorophyll content, while the susceptible genotype (G3) showed significant improvement under treatments. All the exogenous substances possess the ability to help the plant to mitigate the effects of heat stress and support photosynthetic activity. The organic spray like kaolin and molasses effectively reduced internal leaf temperature by developing surface coating, while ABA enhanced internal physiological regulation. The results suggest that the integration of heat tolerant genotypes with suitable treatments can enhance Strawberry resilience to heat stress, which provides a practical alternative for sustainable Strawberry cultivation in tropical regions.