Exploring the effects of water management and silicon or phosphorus pretreatment on arsenic accumulation in rice grains

Abstract

Water management or individual phosphorus (P) and silicon (Si) fertilizers have been demonstrated to be effective in inhibiting arsenic (As) accumulation in rice; however, the nature of their synergistic effects remains unclear. Here, this study innovatively combines complementary water management and seedling enrichment techniques by potted plant experiments to investigate their collaborative impact on As accumulation in rice. The core mechanism involves the regulation of As³⁺ and dimethyl arsenic (DMA), which are prevalent under flooded conditions, by Si transport proteins. In contrast, P primarily regulates As⁵⁺, which is abundant under wet-dry alternating conditions. Here, our results showed that the Si accumulation in the seedlings after Si pretreatment was increased by 38- and 24-fold compared to the control in the two rice varieties Huaghuazhan and Nanjing 46, while P was increased by 3.9- and 3.6-fold by P pretreatment, respectively. Specifically, in the roots of Si-pretreated seedlings, As-related genes were primarily down-regulated, including OsLsi1 (20.0 % and 44.0 %) and OsLsi2 (28.5 % and 29.5 %), while OsABCC1 was upregulated by 54.0 % and 42.7 %. Similarly, in the P-pretreated seedlings, the relative expression of OsPT1 in both varieties was significantly decreased by 43.5 % and 64.7 %, while the relative expression of OsABCC1 in Nanjing 46 was upregulated by 58.5 %. After transplanting seedlings pretreated with Si and P into As-contaminated paddy soil and applying appropriate water management, the translocation of As from roots to stems and from node I to grains was significantly reduced. Consequently, the concentrations of total As, As(III), As(V), and dimethylarsinic acid (DMA) in the grains of both rice varieties were decreased by 12.2–31.6 %, 9.73–29.8 %, 5.23–25.0 %, and 11.9–36.7 %, respectively. Moreover, the structural equation model further confirmed that the cultivation of rice seedlings pretreated with Si or P modulates the expression of arsenic-related genes in rice roots, resulting in a reduction of arsenic content in the rice grains. The coupling effects between water management and seedling pretreatment have been demonstrated to be effective for mitigating As contamination in rice, which holds significant practical value for addressing As pollution in paddy fields.