Hormetic effects of pre-flowering UV-C-dominated radiation enhance yield and fruit quality on tomato

Sustainable agriculture requires strategies to increase food production, such as controlled light spectrum treatments. This study investigated the impact of low, accumulated doses of UV-C and UV-B radiation on the physiology, yield, and fruit quality of Solanum lycopersicum . Plants were treated weekly for four weeks, receiving a total dose of 53 J m⁻² UV-C and 10.29 J m⁻² UV-B. The results demonstrated that while photosynthetic pigment´s concentration decreased toward the end of the treatment, the net photosynthesis and transpiration rates were significantly higher in irradiated plants. This suggests a higher photosynthetic efficiency per unit of chlorophyll, potentially due to structural leaf adjustments that optimize light distribution. The UV treatment triggered a hormetic acclimation response to oxidative stress. Irradiated plants maintained significantly higher levels of ascorbic acid, a better AsA/DHA redox ratio, and increased accumulation of phenolic compounds, flavonols, and anthocyanins in their leaves. These physiological changes were accompanied by a progressive increase in the differential expression of the UVR8 gene, suggesting its involvement in perceiving UV-C radiation. UV-treated plants produced a higher number of flowers and fruits and achieved a greater total harvest weight. Notably, the biochemical analysis of mature fruits revealed substantial improvements in nutritional quality: carotenoids increased by 27%, lycopene by 31%, and total phenols by 18%, resulting in a significantly higher total antioxidant capacity. These findings indicate that pre-flowering application of controlled UV radiation is an effective, non-chemical agronomic tool to enhance crop yield and the concentration of health-promoting bioactives in tomatoes.