The hormone responsible for apical dominance in plants is: MCQ with Answer and Explanation

The hormone responsible for apical dominance in plants is:
A. Cytokinin
B. Gibberellin
C. Ethylene
D. Auxin
Answer: Option D
Solution (By JKSSB Mock Tests)
Auxin produced at the shoot apex inhibits lateral bud growth, a phenomenon called apical dominance. Removing the tip promotes branching.

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Practice More Biology Questions

Question #1
The structure that prevents the collapse of the trachea during breathing is:
A. C-shaped cartilaginous rings
B. Smooth muscle
C. Fibrous tissue
D. Ciliated epithelium

Correct Answer: Option A


Explanation:
The tracheal wall contains C-shaped hyaline cartilage rings that keep the airway open, preventing collapse due to negative pressure during inspiration. Smooth muscle and fibrous tissue connect the rings, ciliated epithelium sweeps mucus upward.

This question belongs to: Science Biology
Question #2
Which enzyme catalyzes the primary carboxylation reaction in the Calvin cycle?
A. Carbonic anhydrase
B. Nitrogenase
C. RuBisCO
D. PEP carboxylase

Correct Answer: Option C


Explanation:
RuBisCO (Ribulose-1,5-bisphosphate carboxylase/oxygenase) is the most abundant protein on Earth and the key enzyme in the Calvin cycle (C3 pathway). It catalyzes the fixation of CO2 by attaching it to Ribulose-1,5-bisphosphate (RuBP) to form a 6-carbon intermediate that immediately splits into two molecules of 3-PGA.

This question belongs to: Science Biology
Question #3
In plant physiology, the 'Imbibition' is a special type of diffusion where water is absorbed by solid particles (colloids), causing them to increase in volume. This process is crucial for:
A. The opening and closing of stomata
B. The translocation of sugars in the phloem
C. The initial absorption of water by dry seeds, leading to germination
D. The ascent of sap in tall trees

Correct Answer: Option C


Explanation:
Imbibition is a physical process where solid, hydrophilic (water-loving) colloidal materials (like cellulose, pectin, proteins, and starch) adsorb water, causing a tremendous increase in their volume and generating significant imbibitional pressure. This process is the very first step in seed germination. When a dry seed is exposed to water, its cell walls and storage materials imbibe water, causing the seed to swell, rupturing the seed coat, and initiating the metabolic activities required for the seedling to grow. It is also responsible for the splitting of rocks by plant roots.

This question belongs to: Science Biology