- A Boron functions as a major structural polymer that progressively displaces most of the cellulose normally found in the wall
- B Boron cross-links pectin (as borate-diol ester) in the primary cell wall, maintaining wall integrity and cell-to-cell adhesion
- C Boron deposits as a waxy cuticle layer across the wall surface, making it largely resistant to water loss over time
- D Boron contributes minimally to cell wall structure, playing a much smaller physiological role than calcium or magnesium
Correct answer: B. Boron cross-links pectin (as borate-diol ester) in the primary cell wall, maintaining wall integrity and cell-to-cell adhesion
Explanation: Boron forms borate ester bonds that cross-link rhamnogalacturonan II (RG-II) in the pectin fraction of primary cell walls. This borate-RG-II complex is essential for wall architecture and porosity. Boron deficiency disrupts pollen germination (borate needed for pollen tube growth) and causes death of growing tips.
Concept context
Essential mineral elements, their roles and deficiency symptoms. Nitrogen fixation and soil nutrition.