Question 1

Which plant hormone is primarily responsible for promoting cell elongation and is involved in phototropism and gravitropism?

Accepted Answer

Auxin

Question 2

A plant is exposed to light from only one direction. Which hormone redistributes to the shaded side, causing the plant to bend toward the light? What is the name of this process?

Accepted Answer

Auxin; phototropism

Question 3

Which of the following best describes the role of abscisic acid (ABA) in plants?

Accepted Answer

Induces stomatal closure during drought stress

Question 4

A scientist applies gibberellin to dwarf pea plants. What is the most likely outcome?

Accepted Answer

The plants will exhibit increased stem elongation

Question 5

Which hormone is most directly involved in the triple response of seedlings to mechanical stress (such as an obstacle in the soil)?

Accepted Answer

Ethylene

Question 6

A plant is exposed to a short day and a long night. According to the concept of photoperiodism, what will happen to a short-day plant?

Accepted Answer

It will flower because it requires a long night

Question 7

Which of the following best explains the mechanism by which phytochrome detects changes in day length?

Accepted Answer

Phytochrome switches between two forms, $$P_r$$ and $$P_{fr}$$, in response to red and far-red light

Question 8

Which process is most directly regulated by the ratio of $$P_{fr} to$$ $$P_r in $$plants?

Accepted Answer

Seed dormancy and germination

Question 9

A mutation causes a plant to be insensitive to ethylene. Which of the following is a likely consequence?

Accepted Answer

The plant will not exhibit the triple response to mechanical stress

Question 10

Which hormone is most closely associated with promoting lateral bud growth and overcoming apical dominance?

Accepted Answer

Cytokinin

Question 11

A gardener wants to delay the senescence (aging) of cut flowers. Which hormone should be applied to achieve this effect?

Accepted Answer

Cytokinin

Question 12

Which of the following best describes the role of gibberellins in seed germination?

Accepted Answer

They stimulate the synthesis of enzymes that mobilize food reserves

Question 13

A plant is exposed to continuous red light followed by a brief pulse of far-red light. What is the likely effect on a long-day plant's flowering response?

Accepted Answer

It will not flower because $$P_{fr} is $$converted back to $$P_r$$

Question 14

Which of the following is a correct sequence of events in the signal transduction pathway for a plant hormone?

Accepted Answer

Reception $$\rightarrow$$ Transduction $$\rightarrow$$ Response

Question 15

Which hormone is most likely to accumulate in seeds during drought conditions, promoting dormancy?

Accepted Answer

Abscisic acid (ABA)

Question 16

A plant is placed horizontally. Which hormone redistributes to the lower side of the stem, causing it to bend upward?

Accepted Answer

Auxin

Question 17

Which of the following best explains why a fruit placed in a sealed bag with a ripe banana ripens faster?

Accepted Answer

The banana releases ethylene, which accelerates ripening

Question 18

Which of the following is an example of a plant's thigmotropic response?

Accepted Answer

A vine coiling around a trellis after contact

Question 19

A mutation in a plant causes it to flower regardless of day length. Which gene is most likely affected?

Accepted Answer

CONSTANS (CO)

Question 20

Which of the following best describes the effect of blue light on plant growth?

Accepted Answer

It triggers phototropism by activating phototropins

Plant Responses to Internal and External Signals (Chapter 39) – Study Guide

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