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Plant Physiology

Photosynthesis, respiration, transport, growth hormones

Key Concepts
  • Photosynthesis: light reactions (in thylakoid) + Calvin cycle (in stroma)
  • C3 plants: fix CO₂ via RuBisCO into 3-PGA; C4 plants use Hatch-Slack pathway
  • Respiration: glycolysis (cytosol) → Krebs cycle (matrix) → ETC (inner mitochondrial membrane)
  • Transpiration: loss of water vapour from leaves; drives water up xylem
  • Plant hormones: auxin (elongation), gibberellin (stem elongation), cytokinin (cell division), ABA (stress), ethylene (ripening)
Important Formulae
Net photosynthesis equation 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ (light energy)
Aerobic respiration (net ATP) 1 glucose → ~36–38 ATP
Glycolysis (net) 1 glucose → 2 pyruvate + 2 ATP + 2 NADH
Quick Tips
  • RuBisCO is the most abundant enzyme on Earth; fixes CO₂ in the Calvin cycle.
  • CAM plants (cacti, succulents) open stomata at night to reduce water loss.
  • Phloem transports sugars (source to sink); xylem transports water and minerals (unidirectional, root to leaf).
Sample Practice Questions

  1. CO₂ fixation in C3 plants occurs via the enzyme:

    • PEP carboxylase
    • RuBisCO
    • Hexokinase
    • ATP synthase
    Show answer

    Answer: RuBisCO

  2. Root pressure is caused by:

    • Transpiration pull
    • Active uptake of mineral ions creating osmotic gradient
    • Gravity
    • Capillary action alone
    Show answer

    Answer: Active uptake of mineral ions creating osmotic gradient

  3. The enzyme RuBisCO catalyses oxygenation reaction in:

    • Dark reactions only
    • Photorespiration
    • Calvin cycle only
    • Glycolysis
    Show answer

    Answer: Photorespiration

  4. Vernalisation is the promotion of flowering by:

    • High temperature
    • Cold temperature
    • Long days
    • Short days
    Show answer

    Answer: Cold temperature

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Practice Questions

Practice 20 randomly selected NEET questions on Plant Physiology. Answers are revealed after each question.

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