Plant Hormones — Set 4
Biology · पादप हार्मोन · Questions 31–40 of 50
Which hormone is primarily responsible for the growth of fruits and flowers?
Correct Answer: C. Auxin
Auxins stimulate the growth of ovary walls into fruit after pollination. They also play a role in the initial development of flower buds. Without this hormone, most plants would fail to develop successful reproductive structures.
Which plant hormone is used to increase the height of sugarcane crops?
Correct Answer: A. Gibberellin
Spraying sugarcane with gibberellins increases the length of the internodes significantly. This results in a higher yield of sugar per acre because more biomass is produced. It is a standard industrial application in sugar production.
Which hormone promotes the germination of seeds by breaking dormancy?
Correct Answer: A. Gibberellin
Gibberellins are the primary signals that tell a dormant seed to start growing. They activate the metabolic pathways required for the embryo to consume stored nutrients. They work in direct opposition to the inhibitory effects of abscisic acid.
Which plant hormone helps in the synthesis of new chloroplasts in leaves?
Correct Answer: C. Cytokinin
Cytokinins promote the differentiation of plastids into mature chloroplasts. This enhances the plant's capacity for photosynthesis and energy production. They also help in maintaining the green color of the leaves.
Which hormone is known as the 'stress hormone' in plants?
Correct Answer: B. Abscisic Acid
Abscisic Acid (ABA) is produced in high amounts when plants face drought or extreme cold. It slows down growth and protects the plant until the stress passes. It is essential for the plant's ability to survive harsh environmental changes.
Which of the following hormones is involved in the ripening of climacteric fruits like bananas?
Correct Answer: A. Ethylene
Bananas produce a large amount of ethylene gas as they ripen, which speeds up the process in surrounding fruit. This is why placing a ripe banana in a bag with green fruit will help them ripen faster. It is a key factor in the global fruit trade.
Which hormone is responsible for the 'Thigmotropism' seen in climbing tendrils?
Correct Answer: D. Auxin
Auxin moves away from the side of the tendril that touches a support. This causes the outer side to grow faster, making the tendril coil around the object. This allows climbing plants to reach sunlight more efficiently.
Which hormone is used in tissue culture to promote root formation in the callus?
Correct Answer: C. High Auxin and Low Cytokinin
A high ratio of auxin to cytokinin in the growth medium encourages the undifferentiated callus to develop roots. Conversely, a high cytokinin to auxin ratio promotes shoot formation. This precise balance is the basis of plant micropropagation.
Which plant hormone is primarily synthesized in the plastids of roots and leaves?
Correct Answer: A. Abscisic Acid
Abscisic Acid is synthesized from carotenoid precursors located within the plastids. It is then transported through the vascular tissue to the target sites. This pathway is shared with certain plant pigments.
Which hormone prevents the 'shedding' of immature fruits and leaves?
Correct Answer: A. Auxin
Auxin maintains the structural integrity of the abscission zone during the growth phase. It inhibits the enzymes that break down the cell walls in that area. This ensures that the fruit stays on the plant until the seeds are ready.