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Agronomy QUESTION #2065
Question 1
Boron deficiency uniquely affects actively growing meristematic tissues and reproductive organs because:
  • Boron is highly mobile in the phloem and accumulates in young tissues
  • Boron is largely immobile in most plant species (except those with polyol transport), so new growth is deprived first; it is essential for cell wall synthesis (cross-linking of pectin), pollen tube growth, and sugar transport✔️
  • Boron toxicity and deficiency produce identical symptoms in young leaves
  • Boron is required exclusively for nitrogen fixation in legume nodules
Correct Answer Explanation
B immobility in most crops means deficiency first appears in shoot tips (hollow heart in brassicas, scorched tips, failure of anthers to dehisce). B is critical for: cell wall pectin cross-linking (borate-diol esters), pollen tube elongation, sugar loading into phloem, and membrane function. Narrow sufficiency range — excess B is toxic.