Question 1

Which of the following is NOT a factor that plants can sense and respond to in their environment?

Accepted Answer

Touch by wind or objects

Question 2

A plant is exposed to light after being grown in darkness. Which sequence correctly describes the signal transduction pathway leading to de-etiolation (greening)?

Accepted Answer

Light activates phytochrome, which increases cGMP and Ca$$^{2+}$$, activating protein kinases and transcription factors.

Question 3

Which experiment led to the discovery of the first plant hormone, and what was the hormone?

Accepted Answer

Darwin and Darwin's phototropism experiment; auxin

Question 4

According to the acid growth hypothesis, how does auxin promote cell elongation?

Accepted Answer

Auxin stimulates proton pumps, lowering cell wall pH and activating expansins.

Question 5

A gardener applies a synthetic auxin-based herbicide to a lawn. Why does this kill dicots but not monocots?

Accepted Answer

Dicots are more sensitive to auxin overdose, leading to uncontrolled growth and death.

Question 6

Which hormone is primarily responsible for promoting seed dormancy and enhancing drought tolerance?

Accepted Answer

Abscisic acid (ABA)

Question 7

A mutant maize plant germinates early, even under dry conditions. Which hormone pathway is most likely disrupted?

Accepted Answer

Abscisic acid (ABA)

Question 8

Which combination of hormones is required for fruit set in many plants, such as grapes?

Accepted Answer

Auxin and gibberellin

Question 9

A plant with its apical bud removed becomes bushier. Which hormone interaction explains this phenomenon?

Accepted Answer

Reduced auxin allows cytokinins to promote axillary bud growth.

Question 10

Which hormone is associated with the triple response in seedlings, including stem thickening, horizontal growth, and slowed elongation?

Accepted Answer

Ethylene

Question 11

A plant mutant fails to undergo the triple response after exposure to ethylene. What is the most likely explanation?

Accepted Answer

The mutant lacks functional ethylene receptors.

Question 12

Which process is regulated by a change in the balance of auxin and ethylene, and is commonly observed in autumn?

Accepted Answer

Leaf abscission

Question 13

Which hormone is most directly involved in stimulating cytokinesis (cell division) in plants?

Accepted Answer

Cytokinin

Question 14

A scientist treats seeds with gibberellin. What is the most likely outcome?

Accepted Answer

Increased seed germination due to activation of enzymes like $$\alpha-$$amylase

Question 15

Which of the following best describes the role of second messengers in plant signal transduction?

Accepted Answer

They transfer and amplify signals from receptors to proteins that cause responses.

Question 16

Which hormone is most likely to accumulate in a plant experiencing drought, and what is its effect?

Accepted Answer

Abscisic acid (ABA); it closes stomata to reduce water loss.

Question 17

A plant is exposed to wind and mechanical touch. Which hormone is most likely to be produced in response to this stress?

Accepted Answer

Ethylene

Question 18

Which of the following best explains why cytokinins are often found in actively growing tissues such as roots, embryos, and fruits?

Accepted Answer

Cytokinins stimulate cell division, which is essential for growth in these tissues.

Question 19

Which hormone is most directly involved in promoting senescence and fruit ripening?

Accepted Answer

Ethylene

Question 20

A plant is treated with an inhibitor of ethylene synthesis. Which of the following is a likely result?

Accepted Answer

Delayed fruit ripening

Plant Signaling and Hormones: Mechanisms and Functions

Study Guide - Practice Questions

Study Guide - Flashcards