Harnessing UV-B and UV-C pre-flowering effect to enhance tomato growth, flowering, and defense under greenhouse conditions

Modern agriculture faces increasing pressure to meet global food demands, leading to intensified practices such as excessive fertilizer use and land expansion, which contribute significantly to greenhouse gas emissions and resource depletion. Climate change further exacerbates these challenges by altering pathogen dynamics and expanding the geographical range of plant diseases. In this context, ultraviolet (UV) light emerges as a promising tool to reduce fertilizer dependency and control plant pathogens under greenhouse conditions. Moderate doses of UV-B and UV-C have been shown to enhance plant growth, flowering, and defence responses. This study investigates the effects of pre-flowering low-doses UV-B and UV-C radiation on the physiology of tomato plants ( Solanum lycopersicum L.), focusing on biometric traits, photosynthetic performance, flowering and oxidative/redox status. Additionally, the potential of UV treatments to reduce infection by Pseudomonas syringae , a model phytopathogenic bacterium, is evaluated. Initial assays revealed that a 3-minute weekly UV treatment significantly enhanced plant height, flower onset, and photosynthetic efficiency, while avoiding photodamage observed at higher doses. Enhanced pigment content and reduced non-photochemical quenching indicated optimal light utilization. Moderate oxidative stress, evidenced by increased malondialdehyde (MDA) levels, was accompanied by elevated phenolic compounds, suggesting an adaptive antioxidant response. Furthermore, plants pre-treated with the 3-minute UV dose exhibited reduced pathogen infection, likely due to the activation of innate immunity as suggested by enhanced PR2 and PR3 expression. These findings support the use of controlled UV irradiation as a powerful strategy to improve crop productivity and resilience in sustainable agricultural systems.