Influence of Organic Fertilizers and Brassinosteroids on Accumulation and Uptake of as and Cd by Rice Seedlings (<i>Oryza Sativa</i> L.) Grown in Soil

The influence of four organic fertilizers (OF) (rapeseed dregs (RD), sesame dregs (SD), bean dregs (BD), and peanut dregs (PD)), two brassinosteroids (Br) (24-epibrassinolide (Br24), and 28-homobrassinolide (Br28)), and their combination (RD+Br and BD+Br) on the accumulation and uptake of arsenic (As) and cadmium (Cd) by rice plants grown in paddy soil spiked with 40 mg kg−1 As and 5 Cd mg kg−1 was performed under waterlogged conditions. The results showed that OF, Br, and their combination significantly decreased Cd contents in shoot and root, but increased As contents in shoot of rice seedling. Iron (Fe) concentration in shoot showed a significant negative correlation with Cd concentration in shoot, but a positive correlation with As concentration in shoot. There was a positive correlation between the Fe content and As or Cd content in plaque. The application of SD, BD, and BD+Br increased the amount of iron plaque, which promoted the adsorption of As, manganese (Mn), copper (Cu), and zinc (Zn) on root surface of rice plant. These findings suggested that the application of OF, Br, and their combination in As-Cd-contaminated paddy soil was an effective approach to decrease Cd uptake by rice plant, but not for As reduction. This is a preliminary study, which has the potential for further enhancing the understanding of uptake mechanisms of As and Cd in rice plant in paddy fields.