Abstract:

This paper aims to investigate the effects of different concentrations of selenium and boron on the growth of radish seedlings, further explore the effects of selenium on the biomass and reactive oxygen species metabolism of radish seedlings under boron toxicity, providing technical support for reducing boron toxicity in radish seedlings. Using radish seedlings (Raphanus sativus ‘Xuedan No.1’) as the test material, a pot experiment was conducted with 5 boron concentrations (0, 125, 250, 500, 750 μmol/L) and 5 selenium concentrations (0, 2.5, 5, 7.5, 10 μmol/L), to study the effects of foliar spraying of different concentrations of selenium and boron on the growth of radish seedlings. Furtherly, 2 boron treatments (250 and 500 μmol/L) were sprayed with Se (0, 5 μmol/L) to study the effect of moderate selenium on physiological characteristics of radish seedlings under boron toxicity. The fresh weight of radish seedlings showed a trend of first increasing and then decreasing with the increase of selenium and boron concentrations sprayed on the leaves. When selenium spraying concentration for radish seedlings was 5 μmol/L, foliar boron spraying concentration was 500 μmol/L, radish seedlings showed symptoms of poisoning. Compared with normal boron application (250 μmol/L), boron toxicity (500 μmol/L) significantly reduced the dry matter weight of radish seedlings, increased the boron content and boron accumulation, decreased the contents of catalase (CAT), peroxidase (POD), ascorbate peroxidase (APX) and glutathione (GSH) in leaves of radish seedlings, and increased the contents of hydrogen peroxide (H₂O₂) and malondialdehyde (MDA). Spraying proper amount of selenium (5 μmol/L), compared with selenium free treatment, the boron content and boron accumulation of radish seedlings under boron toxicity treatment decreased by 40.06% and 37.36% respectively, the activities of POD, CAT, APX antioxidant enzymes in the leaves of seedlings increased by 14.82% and 17.45% respectively, the contents of non enzymatic antioxidants GSH and ascorbic acid (ASA) increased by 13.89% and 5.88% respectively, and the contents of H₂O₂ and MDA decreased by 28.43% and 20.45% respectively. The proper selenium can improve the antioxidant effect of radish seedlings, reduce the accumulation of active oxygen, reduce the toxicity of boron toxicity on radish seedlings, and improve the adaptation range of plants to boron.

Key words: radish, selenium, boron toxicity, antioxidant enzyme activity, non enzymatic antioxidant content