The quantum yield of photosynthesis (φ) represents:

The correct answer is A: The number of CO₂ molecules fixed per photon absorbed. Quantum yield is the ratio of CO₂ fixed to photons absorbed, typically 0.05-0.1 (5-10 CO₂ per 100 photons).

Which of the following is the SI unit of electric potential?

The correct answer is A: Joule per Coulomb. Electric potential is defined as work done per unit charge. SI unit is Joule/Coulomb = Volt. Option D (Watt/Ampere) also equals Volt but option A is more fundamental.

In C4 plants, the first stable compound formed during carbon fixation is:

The correct answer is B: Oxaloacetate. In C4 photosynthesis, CO2 combines with PEP (3-carbon) to form oxaloacetate (4-carbon compound) via the enzyme PEP carboxylase.

What is the primary reason why Venus experiences a runaway greenhouse effect compared to Earth, despite being only slightly closer to the Sun?

The correct answer is A: Venus has a much thicker atmosphere composed primarily of carbon dioxide with clouds of sulfuric acid. Venus's dense atmosphere (90 times denser than Earth's) is composed of 96.5% carbon dioxide with clouds of concentrated sulfuric acid, creating an extreme greenhouse effect with surface temperatures around 465°C. This massive atmospheric composition traps far more infrared radiation than Earth's atm

The process of nitrogen fixation in legumes is performed by which organism?

The correct answer is B: Rhizobium (Nitrogen-fixing bacteria in root nodules). Rhizobium bacteria form symbiotic associations with legume roots, fixing atmospheric N2 into ammonia. The bacteria live in root nodules. This symbiotic relationship is agriculturally significant and frequently tested in competitive exams.

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Difficulty: All Easy Medium Hard 21–25 of 25

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All Physics 106 Chemistry 9 Biology 2 Botany 78 Human Body 4 Disease & Health 2 Space & Astronomy 5 Environment 1

Q.21 Easy Botany

The phenomenon where plants bend towards light source is governed by which hormone?

A Gibberellin

B Auxin

C Cytokinin

D Ethylene

Correct Answer: B. Auxin

EXPLANATION

Auxin causes differential elongation of cells on the shaded side, resulting in phototropic response towards light.

Test

Q.22 Easy Botany

Which element is essential for the synthesis of chlorophyll molecule and forms the central atom in its structure?

A Iron

B Magnesium

C Zinc

D Copper

Correct Answer: B. Magnesium

EXPLANATION

Magnesium (Mg) is the central atom in the chlorophyll molecule, forming a coordinate bond with the porphyrin ring.

Test

Q.23 Easy Botany

The pH of cell sap in plant cells typically ranges between:

A 2-3

B 4-6

C 7-8

D 8-9

Correct Answer: B. 4-6

EXPLANATION

Plant cell sap is slightly acidic due to organic acids like malic acid and citric acid, maintaining pH between 4-6.

Test

Q.24 Easy Botany

Which of the following is the primary pigment responsible for absorbing light energy in the visible spectrum during photosynthesis?

A Chlorophyll a

B Xanthophyll

C Carotenoid

D Anthocyanin

Correct Answer: A. Chlorophyll a

EXPLANATION

Chlorophyll a is the primary photosynthetic pigment that absorbs light in the blue and red regions of the electromagnetic spectrum.

Test

Q.25 Easy Botany

Photosynthesis occurs in?

A Root

B Stem

C Leaf

D Flower

Correct Answer: C. Leaf

EXPLANATION

In chloroplasts of leaves.

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