MICROCLIMATE MODIFICATION STRATEGIES FOR MITIGATING HEAT STRESS-INDUCED POLLEN DAMAGE IN TOMATO (SOLANUM LYCOPERSICUM L.)

Abstract

Heat stress is a primary constraint on tomato (Solanum lycopersicum L.) productivity worldwide, acting most critically during the reproductive stage by impairing pollen viability, germination, and tube elongation, leading to reduced fruit set and yield losses. High temperature disrupts the microsporogenesis process, causes oxidative damage to pollen membranes, impairs carbohydrate metabolism through invertase inactivation, and destabilises the actin cytoskeleton required for pollen tube navigation. Molecular mechanisms underlying these effects include downregulation of meiotic recombinases, sporopollenin biosynthesis genes, and callose synthases, along with disruption of Ca²⁺ homeostasis and premature tapetal programmed cell death. Microclimate modification strategies including shade-net cultivation (30–50% shading), polyhouse and greenhouse systems with evaporative cooling, reflective plastic mulching, anti-transpirant and foliar osmoprotectant sprays, and IoT-based wireless sensor-actuator systems have been demonstrated to reduce canopy temperatures by (2–10°C), preserving pollen viability and improving fruit set under heat stress conditions. The combination of these microclimate interventions with heat-tolerant varieties that constitutively express heat shock proteins and enhanced antioxidant systems has been shown to provide synergistic protection of reproductive function under thermal stress, with yield gains up to 35%. This review synthesises the physiological and molecular basis of heat-induced pollen damage, systematically evaluates the efficacy of six categories of microclimate management strategies, and proposes an integrated framework for maintaining tomato reproductive success under current and projected climate warming scenarios.