Question

A decrease in the level of which hormone releases seeds from dormancy?

a. abscisic acid

b. cytokinin

c. ethylene

d. gibberellic acid

Short answer

a. abscisic acid

Step-by-step solution

Step-1 Introduction

A sensory response of plants towards external stimuli mainly depends upon chemical messengers which are otherwise called hormones. Various aspects of plant growth and development are regulated by plant hormones such as fruit set, flowering, and maturation. It also regulates plant parts elongation and leaf fall. Plant hormones are potentially produced by every cell.

Step-2 Explanation

Plant hormones are group signaling molecules and are unrelated chemical substances that regulate plant development in a positive as well as negative manner. ABA (Abscisic acid) is known to induce seed dormancy by blocking the process of germination and preventing the seed from unnecessary germination in unfavorable conditions. This helps to synthesize storage proteins. As the hormone level gradually decreases over winter, the dormancy period breaks, and the seed is released from dormancy. Subsequently, this will result in germination when the condition is favorable in spring.

The cytokinins are known for the cytokinesis (cell-division)process.

The ethylene is the hormone that induces the ripening of fruits.

A higher level of gibberellic acid promotes the germination of seed.

Step-3 Final Answer

Therefore, option ‘a’ is the correct answer.

Abscisic acid induces dormancy in the seed before germination and prevents germination.