All Free Biology MCQs with Answers

• A. Hydrotropism
• B. Chemotropism
• C. Chemotactic
• D. Seismetactic

Explanation: Chemotropism: Chemotropism is the growth movement of a plant part towards or away from a chemical stimulus.

• A. Epinasty
• B. Thermonasty
• C. Photonasty
• D. Seismonasty

Explanation: Epinasty refers to the downward or outward bending or opening of flower buds or leaf buds.

• A. Auxins
• B. Ethylene
• C. Abscisic acid
• D. Gibberellins

Explanation: Abscisic acid is a plant hormone that plays a crucial role in inducing and maintaining seed and bud dormancy.

• A. geoannual rhythm
• B. lunar rhythm
• C. circadian rhythm
• D. tidal rhythm

Explanation: Circadian rhythms are intrinsic 24-hour cycles that affect physiological, mental, and behavioral functions in living organisms.

• A. phytohormones
• B. Gibberllin
• C. auxins
• D. cytokinesis

Explanation: All plant hormones are collectively known as growth hormones. They include growth promoters, e.g., auxins, cytokinins, gibberellins, etc.

• A. Triple response
• B. Sex expression
• C. Flower initiation
• D. Leaf, flower, and fruit fall

Explanation: Abscisic acid (ABA) is a plant hormone that plays a key role in inhibiting growth and promoting dormancy in plants.

• A. F.A.D
• B. Chlorophyll a
• C. I.A.A
• D. ABA

Explanation: The correct answer is I.A.A (Indole-3-acetic acid), which is an auxin, a class of plant hormones that are essential for cell elongation…

• A. Long day plant
• B. Short day plant
• C. Day-neutral plant
• D. Intermediate plant

Explanation: Tobacco is classified as a short-day plant. These plants require long periods of darkness and shorter daylight hours to initiate…

• A. Gibberellic acid
• B. Indole acetic acid
• C. Flsrcen
• D. Ethylene gas

Explanation: Ethylene gas is known as the 'ripening hormone' because it initiates the ripening process in fruits.

• A. An algae
• B. A fungus
• C. A bacterium
• D. A virus

Explanation: The correct answer is that gibberellins were first isolated from a fungus, specifically Gibberella fujikuroi.

• A. Apical buds
• B. Lateral buds
• C. Parthenocarpy
• D. Root growth

Explanation: Auxins are plant hormones that play a crucial role in regulating plant growth processes.

• A. Auxin
• B. Gibberellins
• C. Cytokinin
• D. Abscisic acid

Explanation: Leaf senescence is a degenerative process among which cellular organelles and biomolecules are broken down and resultant catabolites are…

• A. Flowers
• B. Flower-buds
• C. Leaves (CORRECT)
• D. Fruits

Explanation: Florigen is a plant hormone produced in the leaves. It acts as a long-distance signaling molecule that travels to the shoot apical…

• A. Photoperiodism
• B. Vernalization
• C. Dormancy
• D. Phytochrome

Explanation: Seeds of some plants do not germinate even under favourable conditions. This is called dormancy. It is under endogenous control.

• A. Leaf-tip
• B. Leaf-margin
• C. Leaf-base
• D. Middle-vein

Explanation: Pulvini may be present at the base or apex of the petiole, they consist of a core of vascular tissue within a flexible, bulky cylinder of…

• A. Photo-receptor
• B. Photo-taxis
• C. Photo-tropism
• D. Photo-Periodism

Explanation: Photoperiodism is the ability of plants and animals to measure environmental day length (photoperiod), typically by monitoring night…

• A. 2˚C
• B. 3˚C
• C. 4˚C
• D. 10˚C

Explanation: Vernalization requires an exposure to temperatures between 0-6 °C for several months.

• A. Auxins
• B. Cytokinins
• C. Ethylene
• D. Gibberellins

Explanation: Gibberellin is a plant hormone regulating key processes in plants; many of them are of significant agricultural importance, such as seed…

• A. Spring variety to the winter variety
• B. Winter variety to the spring variety
• C. Winter variety to the summer variety
• D. Summer variety to the winter variety

Explanation: The term vernalization originated from the Latin word Vernalis, which means "of the spring".

• A. 600 nm
• B. 660 nm
• C. 560nm
• D. 730 nm

Explanation: Phytochrome exists in two forms i.e. P 660 and P 730. P 660, a quiescent form, absorbs red light at a wavelength of 660 nm and is…