Plants uptake silica from the soil primarily as orthosilicic acid (H4SiO4).
Here's a breakdown of the process:
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Soil Solution: Silica exists in the soil solution in the form of orthosilicic acid. The concentration typically ranges between 0.2–0.6 mM.
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Uptake by Roots: Plants actively absorb orthosilicic acid from the soil through their roots. The exact mechanisms are still being researched, but it's known that certain transporter proteins play a crucial role.
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Transport to Xylem: After uptake, orthosilicic acid is transported from the root cells to the xylem, the plant's vascular tissue responsible for water and nutrient transport.
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Xylem Transport: Within the xylem, the concentration of orthosilicic acid can transiently reach much higher levels, ranging from 6–18 mM.
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Deposition: The orthosilicic acid is then transported throughout the plant to various tissues and organs, where it's deposited as amorphous silica (SiO2·nH2O), often referred to as phytoliths. This deposition strengthens cell walls and provides other benefits to the plant.
