24. If an Arobidopsis plant, mutated in lycopene biosynthetic pathway is grown in sunny tropical climate in the presence of oxygen:
(1) it would accumulate higher biomass due to higher rate of photosynthesis.
(2) there will not be any influence of this mutation on the rate of photosynthesis and plant growth.
(3) it would show reduced biomass due to photo oxidative damage.
(4) the leaves would be bluish purple in color because of higher accumulation of xanthophylls.

The most accurate answer is (3): The Arabidopsis mutant in the lycopene biosynthetic pathway would show reduced biomass due to photo-oxidative damage. This is because a defect in carotenoid (such as lycopene, which is the precursor to carotenoids like β-carotene and xanthophylls) biosynthesis impairs the plant’s ability to perform photoprotection, resulting in photodamage under high-light conditions.

Lycopene Pathway Mutant Arabidopsis: Impact on Biomass and Photoprotection

Introduction

Key phrase: Arabidopsis lycopene biosynthesis mutation photo-oxidative damage tropical climate

Mutations disrupting the lycopene biosynthetic pathway in Arabidopsis affect levels of carotenoids. In sunny tropical climates, insufficient carotenoids make plants highly vulnerable to photo-oxidative stress, resulting in compromised growth and reduced biomass.​

Explanation of Each Option

• (1) It would accumulate higher biomass due to higher rate of photosynthesis.

  • Incorrect. Mutation in carotenoid biosynthesis leads to less photoprotection, resulting in greater damage and less biomass, not higher. Carotenoids protect against excess light and reactive oxygen species.​

• (2) There will not be any influence of this mutation on the rate of photosynthesis and plant growth.

  • Incorrect. Such mutations do influence photosynthesis and growth because photoprotective pigments are essential for surviving high-light environments.​

• (3) It would show reduced biomass due to photo-oxidative damage.

  • Correct. Plants unable to synthesize carotenoids or lycopene have increased sensitivity to light-induced damage, leading to chlorophyll bleaching, photoinhibition, and reduced growth/biomass under stressful light and oxidative conditions.​

• (4) The leaves would be bluish purple in color because of higher accumulation of xanthophylls.

  • Incorrect. Lycopene pathway mutants produce less carotenoid and xanthophyll, not more. Thus pigments would decrease, not accumulate in excess.​

Key Facts: Lycopene Mutant Arabidopsis

• Carotenoids (including lycopene, β-carotene, and xanthophylls) protect chlorophyll and membranes from oxidative damage.

• Mutation in lycopene biosynthetic pathway results in less carotenoid, greater photodamage, lower leaf biomass.

• Blue-purple coloration is unrelated; such mutants often show chlorosis or bleaching instead.​