LAUSR

Simple Summary Sudden cold snaps, often accompanied by rapid fluctuations in sunlight, disrupt leaf light-harvesting mechanisms. In mulberry trees, this combination weakens the photosynthetic apparatus, decreases photosynthetic and water-use efficiency, and increases oxidative stress. To investigate potential mitigation, we tested the effect of a small, safe dose of hydrogen sulfide (H2S), a naturally occurring gas in plants. Young mulberry plants were exposed to low temperatures and fluctuating light, with or without a one-time leaf spray that gradually releases H2S. Under stress, photosynthesis declined, and oxidant levels increased. H2S treatment, however, enhanced photosynthesis and water-use efficiency, reduced oxidant accumulation, and activated endogenous protective enzymes. Two mechanisms were observed: excess light energy was dissipated as heat, and antioxidant defenses were enhanced. These effects stabilized energy flow and improved carbon utilization under stress. The results indicate that low-dose H2S could serve as a practical strategy for mitigating the impact of erratic spring weather on fruit tree yield.