Factors Affecting Photosynthesis — NEET Biology MCQs with Solutions
Free NEET Biology Factors Affecting Photosynthesis MCQs with step-by-step solutions (6 questions). Part of Photosynthesis in Higher Plants. Practise online on Prepizo — no login needed.
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Questions with solutions
Q1 — Factors Affecting Photosynthesis · easy · theory
Blackman's law of limiting factors states that when several factors affect a process, its rate is limited by the factor that is:
A. At its maximum
B. Nearest to its minimum value ✓ Correct
C. Constant
D. Unrelated to the rate
Solution: The pace of the process is set by the most limiting (scarcest) factor at that time.
Q2 — Factors Affecting Photosynthesis · easy · theory
Which is NOT an external factor affecting photosynthesis?
A. Temperature
B. CO₂ concentration
C. Light
D. Number of chloroplasts (internal) ✓ Correct
Solution: External factors: light, CO₂, temperature, water. Internal factors include chlorophyll amount, leaf age, chloroplast number.
Q3 — Factors Affecting Photosynthesis · medium · theory
At light saturation, further increase in light intensity does not raise the rate because:
A. Temperature falls
B. Chlorophyll is destroyed
C. Another factor (e.g. CO₂) becomes limiting ✓ Correct
D. Light is no longer absorbed
Solution: Beyond the saturation point, light is no longer limiting; some other factor caps the rate.
Q4 — Factors Affecting Photosynthesis · medium · theory
For most C3 plants, increasing CO₂ concentration up to ______ increases photosynthesis, and this is used commercially in greenhouses:
A. ~78%
B. ~0.05% (higher than atmospheric) ✓ Correct
C. ~21%
D. ~0.001%
Solution: Raising CO₂ (to ~0.05%) boosts C3 photosynthesis (CO₂ fertilisation); C4 plants saturate at lower CO₂.
Q5 — Factors Affecting Photosynthesis · hard · theory
Very high light intensity can DECREASE the photosynthetic rate due to:
A. Excess CO₂
B. Photo-oxidation (breakdown) of chlorophyll ✓ Correct
C. Increased water
D. Low temperature
Solution: Excessive light causes photo-oxidative damage (photoinhibition) to the pigments and photosynthetic apparatus.
Q6 — Factors Affecting Photosynthesis · hard · theory
The temperature response of photosynthesis differs between C3 and C4 plants in that:
A. Both have identical optima
B. Temperature has no effect on C4
C. C4 plants have a higher temperature optimum than C3 plants ✓ Correct
D. C3 plants tolerate higher temperatures
Solution: C4 plants are adapted to warmer, high-light environments and photosynthesise optimally at higher temperatures than C3 plants.