Effects of tris (2-chloroethyl) phosphate on the seed germination and antioxidant properties of alfalfa

Tris (2-chloroethyl) phosphate (TCEP) is a new type of flame-retardant material that continues to accumulate in the environment and causes harm to the natural ecology and human health. In this experiment, the effects of TCEP on the seed germination characteristics, reactive oxygen species production, and antioxidant system were studied using widely cultivated alfalfa as the raw material, with different concentrations of TCEP and different treatment times. The results showed that high concentrations of TCEP (≥120 mg·L⁻¹) had a significant inhibitory effect on alfalfa germination, and the degree of inhibition gradually increased with an increase in the treatment concentration. Histochemical staining and UV spectrophotometric determination showed that the degree of lipid peroxidation of the reactive oxygen species in TCEP-treated alfalfa sprouts was exacerbated, and the SOD, CAT, POD, APX, DHAR, MDHAR, and GSH-Px of the sprouts increased significantly on the third day, and the contents of GSSH and DHA also increased. On day 5 of the treatment, the SOD, CAT, DHAR, and MDHAR activities and GSSH content increased. The above results show that under TCEP stress, the normal progress of AsA-GSH circulation in alfalfa is disturbed, and the oxidation degree of AsA and GSH increases, thereby destroying the redox balance in the alfalfa shoots, causing a large accumulation of reactive oxygen species, and finally inhibiting alfalfa germination. This study investigated the tolerance of alfalfa to TCEP pollution and the toxic effects and specific mechanisms of TCEP on alfalfa germination, which will provide a theoretical basis for the restoration of TCEP pollution in grasslands that may occur in the future.