Response of Vicia faba to short-term uranium exposure: chelating and antioxidant system changes in roots.

Uranium (U) phytotoxicity is an inherently difficult problem in the phytoremediation of U-contaminated environments. Plant chelating and antioxidant systems play an authoritative role in resistance to abiotic stress. To reveal the toxicity of U, the changes of chelating system, osmoregulatory substances and antioxidant systems in Vicia faba roots were studied after short-term (24 h) U exposure. The results indicated that the development of lateral roots and root activity of V. faba were significantly inhibited with U accumulation. Compared with the control, plant chelating systems showed significant positive effects after U exposure (15 - 25 µM). Osmoregulatory substances (proline and soluble protein) increasingly accumulated in roots with increasing U concentration, and O2- and H2O2 rapidly accumulated after U exposure (15 - 25 µM). Thus, the contents of malondialdehyde (MDA), a marker of lipid peroxidation, were also significantly increased. Antioxidant systems were activated after U exposure but were inhibited at higher U concentrations (15 - 25 µM). In summary, although the chelating, osmotic regulation and antioxidant systems in V. faba were activated after short-term U exposure, the antioxidases (CAT, SOD and POD) were inhibited at higher U concentrations (15 - 25 µM). Therefore, the root cells were severely damaged by peroxidation, which eventually resulted in inhibited activity and arrested root development.

Effects of U on the growth, reactive oxygen metabolism and osmotic regulation in radish (Raphanus sativus L.).

Uranium (U) is a non-essential and toxic element, so it is necessary to study the physiological mechanism of plant response to U stress. The present study evaluated the growth status, reactive oxygen metabolism and osmotic regulation system in radish (Raphanus sativus) under U stress (0, 25, 50 and 100 µM). The results showed that U had no significant effect on the germination of radish seeds but inhibited the growth of seedlings, such as reduced root activity and increased plasma membrane permeability. U is mainly distributed in radish roots, so it poisons the roots more than the aboveground parts. When U concentration was 25 µM, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities in radish were increased to cope with the oxidative stress caused by U stress, and the accumulation of proline and soluble sugar was increased to maintain cell turgor. However, under high concentration (100 µM), the damage of radish root was serious; thus, the SOD, CAT and soluble sugar could not respond to U stress. In conclusion, the identification and characterization of U-stress responses in genuine U-tolerant plants would improve our knowledge on the detoxification of this radionuclide.

[Research progress in the osteogenetic mechanism of strontium].

Strontium (Sr) is an essential trace element and widely exists in nature. It plays an important role in the in vivo regulation of bone metabolism. Sr locates below Fe in the periodic table, and its chemical structure and polarity are similar to those of Ca. It can induce bone mesenchymal stem cells to differentiate into osteoblasts by inhibiting the activity of osteoclasts and reducing bone resorption. It promotes bone formation through a series of related pathways. The mechanism of Sr regulation of bone metabolism has been extensively researched in recent years. The current study aims to investigate the mechanism of Sr and provide a theoretical basis for its clinical application.