The absorption and accumulation of As at different stages of rice growth are significantly different. To study the key growth stages of As accumulation in brown rice and to determine the contribution of As accumulation at different growth stages to As contribution in brown rice, a rice hydroponics experiment was carried out by adding external As during the different rice growth stages: tillering stage (30 d), jointing stage (16 d), booting stage (13 d), filling stage (17 d), dough stage (15 d), maturity stage (13 d), and full growth period (104 d). The results showed that: ① As stress at different growth stages had a significant effect on the biomass of rice plants. In comparison with the control CK, the treatments of As stress with five single-stages decreased the rice biomass, except during the tillering stage. Among these treatments, although the As stress at booting stage had the lowest rice biomass, the biomass of all the rice plants were higher than that for As stress in the full growth period. ② The content of As in brown rice for all the treatments of As stress at six single-stages, ranging from 0.08-0.24 mg ·kg-1, was higher than that of CK. Among these six treatments, the As stress at booting stage had the highest As content in brown rice, accounting for 64.9% of the As content in the full growth period. ③ The accumulation of As in brown rice for all the treatments of As stress at six single-stages was higher than that of CK, and ranged from 1.4-1.5 μg ·plant-1. Among these six treatments, the As stress at booting stage had the highest As accumulation, followed by filling stage. The accumulation of As in brown rice treated with As stress was highest in the full growth period with a value of 5.7 μg ·plant-1. ④ The relative contribution of As stress at the booting stage was the highest for the As accumulation in brown rice and reached to 40.3%, followed by filling stage with 26.0%. Therefore, the rice growth stages of the booting stage and filling stage were the key stages of As accumulation in brown rice.
Keywords: Arsenic stress; accumulation rate; growth stage; relative contribution rate; rice.