Hormetic growth of Pinus pseudostrobus seedlings exposed to low-dose gamma and X-ray irradiation

Mexico ranks among the countries with the highest deforestation rates, increasing the demand for high-quality forest seedlings ofvaluable species such asPinus pseudostrobus Lindl., which face germination limitations due toseed dormancy and low viability. Ionising radiation has emerged asanalternative pregermination treatment capable ofinducing adaptive responses inplants through hormesis. This study evaluated the effects ofdifferent doses ofgamma radiation (60Co) and high-energy X-rays (linear accelerator, 6 MeV) onthe germination, growth, and quality ofP. pseudostrobus seedlings. Atotal of1440 seeds were irradiated per radiation source with 12 doses (0–25 Gy) and sown under nursery conditions inacompletely randomised design. Germination parameters, morphological traits, photosynthetic pigment content, and quality indices were analysed. With both radiation sources, low doses (0.5–1.5 Gy) significantly enhanced germination, chlorophyll content, and seedling height and diameter, while doses above 15 Gy inhibited these responses. TheLD50(median lethal dose) was estimated at20 Gy for gamma rays and 12 Gy for X-rays, whereas GR50(median growth reduction dose) exceeded 45 Gy inboth treatments. These findings demonstrate that low radiation doses elicit abeneficial hormetic effect inP.pseudostrobus, representing a viable biotechnological approach to improve seedling production and ecological reforestation efficiency.