Effects of ⁶⁰Co-γ radiation on seed germination， seedling growth， and physiological characteristics of Taraxacum kok-saghyz Rodin

【Objective】 This study aimed to investigate the effects of ⁶⁰Co-γ radiation mutagenesis on seed germination， seedling growth， and physiological characteristics of Taraxacum kok-saghyz Rodin， to determine the optimal radiation dose， providing theoretical basis for breeding novel superior varieties and enriching Taraxacum kok-saghyz Rodin germplasm resources. 【Method】 Seeds of Taraxacum kok-saghyz Rodin K445 were used as experimental materials. Seeds were treated with different ⁶⁰Co-γ radiation doses 0 （control，CK）， 60， 100， 140， 180 Gy to conduct comparative analysis of the effects of different radiation dose treatments on seed germination indicators， seedling morphological indicators， and physiological indicators of Taraxacum kok-saghyz Rodin. 【Result】 After different doses of ⁶⁰Co-γ radiation， the germination rate， germination potential， germination index， and seedling emergence rate of Taraxacum kok-saghyz Rodin were significantly decreased compared to control group （P<0.05， the same below）， exhibiting a gradual decreasing trend with increasing radiation dose， indicating that seed germination was markedly inhibited. After different doses of ⁶⁰Co-γ radiation for Taraxacum kok-saghyz Rodin seeds， seedling growth was markedly inhibited， with marked morphological radicle differences between different dose groups； compared with the control group， radicles were noticeably shortened after radiation， with brown necrosis at the root tips， and radicle necrosis turned severer as radiation dose increased. As radiation dose increased， both seedling emergence rate and relative seedling rate of Taraxacum kok-saghyz Rodin seeds showed a decreasing trend， with significant differences between dose treatment groups； leaf length， root length， dry weight， and fresh weight of seedlings also generally decreased， indicating that different ⁶⁰Co-γ radiation doses markedly inhibited seedling growth of Taraxacum kok-saghyz Rodin， and seedling growth inhibition was intensified as radiation dose increased. By establishing the optimal regression equation of radiation dose （x） and relative seedling rate （y） as y=-0.550x+84.825， R²=0.828， the semi-lethal dose （LD₅₀） for 50% relative seedling rate of Taraxacum kok-saghyz Rodin was calculated to be 63.32 Gy， which was the recommended radiation dose. As radiation dose increased， contents of hydrogen peroxide （H₂O₂） and malondialdehyde （MDA） first increased and then decreased， all significantly higher than those in the control group； activities of peroxidase （POD）， superoxide dismutase （SOD）， and catalase （CAT） in seedling leaves showed an initial increase followed by a decrease， all significantly higher than the control group. 【Conclusion】 Taraxacum kok-saghyz Rodin exhibits high sensitivity to ⁶⁰Co-γ radiation， with an LD₅₀ of only 63.32 Gy. Under ⁶⁰Co-γ radiation， the seed germination and seedling growth of Taraxacum kok-saghyz Rodin show dose dependency and inhibitory effects. Appropriate radiation dose can activate antioxidant defense system in Taraxacum kok-saghyz Rodin seedlings， but excessive doses can damage the defense system， causing increased lipid peroxidation of cell membranes.