Effects of U stress on physiological tolerance characteristics and mineral element distribution of sunflower seedlings

The metabolism of plant mineral nutrients is crucial for plant growth and development and is a key parameter for characterising the growth state of plants in various environments. However, as a non-essential element for plants, radionuclide uranium readily accumulates in the roots, causing root toxicity and metabolic disorders of plant mineral nutrients. We used hydroponic sunflowers as experimental materials to explore the uranium tolerance features of sunflower seedlings and to compare the absorption of mineral nutrients by different root components and organs of the sunflower. The results showed that the absorption and accumulation of uranium by different sunflower varieties and various parts of sunflowers differed significantly, and uranium treatment severely damaged the sunflower root tissue. Simultaneously, uranium predominantly accumulated in the cell walls of the root tissue, contributing to sustained damage. Furthermore, antioxidant enzymes play a vital role in preventing damage caused by uranium stress. Uranium stress disrupts the photosynthetic metabolism of sunflowers. The levels of most mineral elements in the roots and leaves of sunflowers increased significantly after treatment with 0.01 mM uranium. Uranium treatment significantly reduced the Mg content of TY007 and S668 leaves by 11.03–77.68 % and 28.51–58.40 %, respectively. This study offers a scientific basis for remediating uranium contamination in urban and rural brownfield sites.