Spraying silicon to decrease inorganic arsenic accumulation in rice grain from arsenic-contaminated paddy soil.

Area of Science:

• Agricultural Science
• Environmental Chemistry
• Plant Physiology

Background:

• Arsenic (As) contamination in paddy soils poses a significant risk to rice safety.
• Silicon (Si) addition to soil reduces As uptake, but foliar application is an underexplored alternative.
• Optimal timing and methods for foliar Si application to mitigate As accumulation in rice remain unclear.

Purpose of the Study:

• To investigate the efficacy of foliar silicon (Si) application at different growth stages for reducing arsenic (As) accumulation in rice grains.
• To determine the impact of Si application timing on inorganic As concentrations in various rice tissues.
• To elucidate the physiological mechanisms underlying Si's role in mitigating As uptake and translocation.

Main Methods:

• Conducted soil pot experiments using As-contaminated paddy soil and rice.
• Applied silicon (Si) solutions via foliar spraying at distinct rice growth stages (tillering, jointing, etc.).
• Analyzed total and inorganic As concentrations in rice husks, grain, bran, and polished rice; measured Si concentrations and transporter gene expression.

Main Results:

• Foliar Si application at tillering or jointing stages significantly reduced As in husks and grain by inhibiting translocation.
• Application at the tillering stage markedly decreased inorganic As in rice bran (27.3%) and polished rice (61.4%).
• Si solution with Tween 80 reduced total As by 48.8% and inorganic As in grain by 49.2%, linked to downregulated Si transporters (Lsi1, Lsi2, Lsi6).

Conclusions:

• Foliar Si application is a viable strategy to reduce inorganic As accumulation in rice grains from contaminated soils.
• Application during the tillering stage is most effective for minimizing As in edible rice portions.
• The mechanism involves enhanced Si uptake, leading to downregulated Si transporters and reduced As uptake and transport.