Answer: Mobile nutrients are redistributed from older to younger leaves during deficiency; immobile nutrients remain in older leaves.
- A Mobile nutrients tend to be absorbed from the surrounding soil at a somewhat faster physical rate in typical laboratory settings
- B Mobile nutrients are redistributed from older to younger leaves during deficiency; immobile nutrients remain in older leaves
- C Immobile nutrients are largely excluded from readily entering the plant body once absorbed under usual circumstances according to most researchers
- D Mobile nutrients are mostly restricted to the broad category of macronutrients like N and K in the majority of cases studied
Correct answer: B. Mobile nutrients are redistributed from older to younger leaves during deficiency; immobile nutrients remain in older leaves
Explanation: Mobile nutrients (N, P, K, Mg) are retranslocated from older to younger tissues during deficiency; deficiency symptoms appear first in OLD leaves. Immobile nutrients (Ca, Fe, B, Cu) cannot be moved; deficiency symptoms appear in YOUNG leaves first.
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.