Abstract:A hydroponic experiment was carried out to explore the effects of Si/As ratios (0:1,100:1 and 200:1) on the uptake, efflux, translocation and accumulation of arsenic in rice seedlings that were grown in nutrient solution containing 10 μmol/L arsenite or arsenate for 12, 24,48 h. The results showed that Si/As of 200:1 reduced arsenite uptake rate compared to Si/As of 0:1, accounting for 30.7% (P<0.05), when rice was exposed to nutrient solution with arsenite and silicon for 12 h. The uptake rates of arsenite of rice gradually decreased and the effect of different Si/As ratios reduced with the prolongation of exposure time. Furthermore, compared to Si/As of 0:1, the ratios of Si/As at 100:1 and 200:1 inhibited the translocation of arsenite from roots to shoot and the concentrations of As(Ⅲ) were decreased by 51.2% and 56.9%, respectively, when rice seedlings exposed to nutrient solution with arsenite for 48 h, at the same time, the concentrations of As(Ⅲ) in rice shoots were significantly lower than Si/As of 0:1, accounting for 50.7% and 67.2%, respectively. When rice seedlings were exposed to arsenate nutrient solution for 12 h, Si/As of 100:1 promoted the uptake rate of arsenate by rice, which was 82.3% higher than Si/As of 0:1. However, the ratio of Si/As of 200:1 inhibited the uptake rates of arsenate, arsenite efflux by rice roots and translocation of As(Ⅲ) after 24 h for exposure to asenate, accounting for 28.0%, 41.9% and 39.9%, respectively. The translocation of As(Ⅲ) from root to shoot with Si/As of 200:1 was 57.9% lower than that of Si/As of 100:1 after 48 h of exposure time. In addition, the concentrations of As(Ⅲ) in rice shoots in the treatment of Si/As ratio at 100:1 and 200:1 for 24 h or 48 h were significantly lower than the control, accounting for 53.6% and 75.0%, 25.0% and 52.8%. In addition, there was a significant positive correlation between the uptake of As(V) and the efflux of As(Ⅲ) in rice roots (r=0.921, P<0.01), which was not affected by Si/As and exposure time. In summary, when rice seedlings were exposed in nutrient solution with As(Ⅲ) or As(V) for 12~48 h, the ratio of Si/As at 200:1 significantly inhibited arsenic uptake, As(Ⅲ) efflux and translocation of As(Ⅲ) from root to shoot in rice.