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Zorluk: OrtaPlant Nutrition and Photosynthesis

A hydroponic experiment was set up to study the physiological roles of micronutrients in crop growth. Plants grown in a medium lacking a specific trace element exhibited normal chlorophyll synthesis, yet their rate of oxygen evolution during the light-dependent stage of photosynthesis dropped significantly. Which of the following mineral elements is directly involved as a cofactor in the photolysis of water to cause this effect?

  1. ManganeseCevap
  2. B
    Nitrogen
  3. C
    Phosphorus
  4. D
    Potassium

Cevap

Manganese is the essential micronutrient required as a cofactor for the oxygen-evolving complex during photolysis of water.
Manganese ions (Mn2+Mn^{2+}) are essential cofactors for the oxygen-evolving complex (OEC) integrated within Photosystem II in the thylakoid membranes. Manganese undergoes reversible oxidation states to catalyze the photolytic cleavage of water into oxygen gas, protons, and electrons. Without manganese, water photolysis fails and oxygen release drops even if chlorophyll concentration remains normal.

Adım Adım Çözüm

1
Analyze the experimental observations
Chlorophyll levels remain normal, indicating pigment production is intact, but oxygen evolution during the light stage is impaired.
Oxygen gas is liberated exclusively during photolysis (light-dependent splitting of water) within Photosystem II.
2
Identify the enzymatic requirement for photolysis
Photolysis relies on the oxygen-evolving complex (OEC), which requires specific mineral cofactors to oxidation-split water molecules (2H2O→O2+4H++4e−2H_2O \rightarrow O_2 + 4H^+ + 4e^-).
Manganese (Mn2+Mn^{2+}) and chlorine (Cl−Cl^-) ions serve as essential cofactors facilitating electron extraction from water.
3
Differentiate from other mineral deficiency symptoms
Deficiencies in Nitrogen or Magnesium impair chlorophyll synthesis causing chlorosis, whereas Manganese deficiency impairs oxygen production directly without initially reducing chlorophyll content.
Targeted functional assignment isolates Manganese as the correct mineral element.

Anahtar Kavram

Role of Manganese as a cofactor in water photolysis and oxygen evolution during photosynthesis
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Konular

Plant Nutrition and Photosynthesis

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