Modulation of red wavelengths influences the response of <i>V. Radiata</i> plants to ionizing radiation: Implications for growth in closed ecological life‐support systems in space

Space is considered one of the harshest environments for living organisms, where ionizing radiation poses a significant threat to biological systems. Although plants exhibit higher resistance to radiation than animals, their photosynthetic machinery remains highly vulnerable. Given the role of plants in Controlled Ecological Life Support Systems (CELSSs), understanding how environment influences plant performance is critical for space missions. This study investigated the combined effects of X-ray irradiation (0.3, 10, or 20 Gy) and light quality (white, red, or red-blue LEDs) on young Vigna radiata L. plants. To assess plant potential acclimation strategies to radiation, we evaluated key functional traits, focusing on growth and photosynthetic performance. Specifically, we quantified in vivo chlorophyll fluorescence, photosynthetic pigments (chlorophylls, carotenoids), and expression of two major photosynthetic proteins: D1 (PSII core) and Rubisco. To our knowledge, no previous studies have explored how specific light wavelengths modulate plant responses to ionizing radiation during early development stages. Our results showed that red light enhances biomass allocation to shoots, promotes pigment accumulation, specifically at 0.3 and 10 Gy, and maintains higher photochemical efficiency and protein expression even at the highest radiation dose, compared to other light wavelengths. Maintaining an appropriate light environment during initial phases of growth enhances photosynthetic performance, reducing the harmful effects of X-rays, thus enabling plants to fulfil their ecological role in CELSSs.