Free Plant Growth Regulators MCQs with Answers

11. All of the following are methods to break the seed dormancy EXCEPT

• A. Exposing the seeds to heat
• B. Treating the seed coats with acid
• C. Keeping the seed coats hard and dry
• D. Giving low temperature treatment to seeds

Explanation: The only option that does not break dormancy is keeping the seed coats hard and dry, hence option C is correct.To break seed dormancy, methods like exposing seeds to heat, treating seed coats with acid, and giving seeds low-temperature treatment are effective. Heat softens hard seed coats, acid mimics digestive processes that weaken the coat, and cold stratification triggers biochemical changes in seeds with physiological dormancy. In contrast, keeping seed coats hard and dry does not break dormancy.

12. Biennials and perennial plants are stimulated to produce flowers by exposing them to low temperature. In these plants, the low temperature stimulus is received by the I. Shoot apex of a mature stem II. Embryo of the seed III. Leaves

• A. I only
• B. I and II
• C. III only
• D. II and III

Explanation: Only option I and II are correct as In many biennials (e.g., carrot, beet) and some perennials, the shoot apical meristem is the site where vernalization occurs.The shoot apex contains meristematic tissue, which can respond to cold and later initiate flowering when conditions become favorableIn some plants, especially winter annuals and cereals like wheat, barley, and rye, the embryo inside the seed perceives the cold treatment.(option I)Seeds are exposed to low temperatures (called stratification) to break dormancy and promote flowering after germinationLeaves are not the primary site for vernalization.(option II)Although leaves can sense photoperiod (day length) through phytochrome, they cannot perceive cold stimulus for vernalization.The cold must act on meristematic tissues, not on mature leaf cells, which lack the ability to initiate flowering signals in response to cold.(option III)

13. The experimental set-up that is used MAINLY to demonstrate positive geotropism in plants is

• A. A
• B. B
• C. C
• D. D

Explanation: Only option B shows positive geotropism as pea seedling growing in a porous pot and sand, with roots growing downwards demonstrates Positive Geotropism. The image clearly shows the roots of the pea seedling growing vertically downwards, following the pull of gravity, which is the definition of positive geotropism. The setup ensures the plant is growing in a condition where the root's response to gravity can be easily observed.

14. A farmer wants to ripen the raw apples in his farm. For this purpose, he keeps the raw apples with the apples that are already ripened.The hormone produced by the ripened apples is

• A. Auxin
• B. Ethylene
• C. Cytokinin
• D. Gibberellin

Explanation: The correct answer is Option B, also known as ethylene, is a plant hormone that is crucial in the ripening of fruits. It acts by breaking down cell walls, converting starches to sugars, and decreasing acidity, which collectively contribute to the ripening process. While auxins, cytokinins, and gibberellins have their roles in plant growth and development, they are not directly responsible for the fruit ripening process. Auxins primarily aid in cell elongation, cytokinins in cell division, and gibberellins in growth, but ethene is the key hormone for ripening.

15. During seed dormancy, seeds do not germinate because the seeds

• A. Are devoid of all kinds of nutrients
• B. Could produce fruits with hard fruit wall
• C. Require a period of rest before germination
• D. Could produce plants that are vulnerable to diseases

Explanation: The correct answer is that seeds require a period of rest before germination (Option C). Seed dormancy is a survival strategy to prevent germination during unfavorable conditions. This allows seeds to remain viable until environmental conditions are optimal for growth. Option A is incorrect because seeds contain nutrients necessary for early growth. Option B is irrelevant as the fruit wall's hardness doesn't affect seed dormancy. Option D is incorrect because dormancy is unrelated to disease vulnerability.

16. In most of the plants, intercalary meristems are situated at the

• A. Root apex
• B. Shoot apex
• C. Base of internodes
• D. Lateral sides of shoots

Explanation: Intercalary meristems are primarily found at the base of internodes in many plants and are responsible for the elongation of plant sections such as stems and leaves. This is especially common in grasses and monocots where growth needs to occur from the base upwards. The root apex and shoot apex are sites for apical meristems, which facilitate root and shoot elongation respectively. The lateral sides of shoots, however, are associated with lateral meristems, which are involved in the thickening of the plant stem or trunk (secondary growth).

17. Which of the following promotes both leaf and fruit growths?

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

Explanation: Gibberellins promote leaf and fruit growths.

18. Pick the paratonic movement from the following:

• A. Nastic.
• B. Growth.
• C. Turgor.
• D. Tactic.

Explanation: Nastic movements are a type of paratonic movement.

19. It is known that red light_ flowering in the long day plants.

• A. Synchronizes.
• B. Promotes.
• C. Inhibits.
• D. Does not affect.

Explanation: It has been found that red light Inhibits flowering the short day plants but promotes flowering in long day plants.

20. In plants, the red light favours:

• A. Enhancement of cell differentiation
• B. Maturation of the cells
• C. Elongation of cells
• D. Enhancement of cell division

Explanation: Explanation:Red light favours elongation of cells and blue light enhances cell division but retards cell enlargement.When red light can influence the differentiation of certain cell types in plants, it is not the primary effect of red light.Red light is not known to have a significant effect on the maturation of cells in plants.Red light is also not known to have a direct effect on cell division in plants, although it can indirectly influence cell division by promoting plant growth and providing the necessary conditions for cell division to occur.