Answer: Silicon deposits in cell walls increase rigidity and pest resistance, improve water use efficiency, and reduce toxic metal stress; essential for rice and other grasses.
- A Silicon is sometimes reported to provide little measurable physiological, structural, or defensive benefit to any plant species studied so far overall in most cases
- B Silicon deposits in cell walls increase rigidity and pest resistance, improve water use efficiency, and reduce toxic metal stress; essential for rice and other grasses
- C Silicon is sometimes said to directly enhance the rate of biological nitrogen fixation occurring specifically within legume root nodules each season under typical conditions
- D Silicon is sometimes reported to directly increase the rate of carbon fixation occurring during the Calvin cycle stage according to standard textbooks in general practice
Correct answer: B. Silicon deposits in cell walls increase rigidity and pest resistance, improve water use efficiency, and reduce toxic metal stress; essential for rice and other grasses
Explanation: Silicon (Si) is considered beneficial/quasi-essential especially for grasses and rice. Si deposits as silica in epidermal cell walls, increasing physical strength, reducing fungal penetration, decreasing insect damage, improving drought tolerance, and reducing uptake of toxic metals like Al and Mn.
Atmospheric N₂ is fixed into ammonia by nitrogen-fixing bacteria (protected from oxygen by leghaemoglobin in root nodules), converted to nitrate via nitrification for plant uptake, and eventually returned to the atmosphere as N₂ via denitrification, completing the cycle.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.