Answer: Chloride is a micronutrient essential for photosynthesis (water-splitting in PSII), stomatal regulation (counter-ion for K+ in guard cells), and osmoregulation.
- A Chloride ions are sometimes reported to be largely non-essential and to play little measurable physiological role in most plant species studied as frequently observed in practice
- B Chloride is a micronutrient essential for photosynthesis (water-splitting in PSII), stomatal regulation (counter-ion for K+ in guard cells), and osmoregulation
- C Chloride is sometimes said to function chiefly as a macronutrient required mainly for cross-linking pectin molecules within plant cell walls broadly in many documented cases
- D Chloride is sometimes reported to play a meaningful physiological role mainly within salt-tolerant halophyte plant species, rarely elsewhere according to conventional understanding
Correct answer: B. Chloride is a micronutrient essential for photosynthesis (water-splitting in PSII), stomatal regulation (counter-ion for K+ in guard cells), and osmoregulation
Explanation: Chloride is a micronutrient: (1) Required as cofactor for PSII water-splitting complex; (2) Serves as counter-ion to K+ during stomatal opening; (3) Involved in turgor regulation. Plants need very small amounts (<0.01% dry weight) but deficiency disrupts photosynthesis and wilting occurs.
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.