Plant Responses to Internal and External Signals

Question 1

The process by which a signal from the environment is received, converted, and transmitted within a plant cell is called:
a) Photosynthesis
b) Cellular respiration
c) Signal transduction
d) Auxin transport

Answer 1

c) Signal transduction

Question 2

What are chemical messengers within plants that coordinate growth, development, and responses to stimuli?

Answer 2

Plant hormones

Question 3

The binding of a signal molecule to a ____ on the plasma membrane initiates signal transduction pathways in plant cells.

Answer 3

receptor

Question 4

TF: Second messengers, like cyclic nucleotides and calcium ions, are involved in relaying the signal within the cell and triggering cellular responses.

Answer 4

True

Question 5

How does the action of plant hormones differ from that of animal hormones? Consider factors like receptor location and target cells.

Answer 5

Plant hormones often bind to receptors on the cell surface or within the cytoplasm, while animal hormones frequently have receptors inside the nucleus. Plant hormones can have a broader range of target cells, whereas animal hormones often target specific tissues.

Question 6

Which plant hormone is primarily responsible for stimulating cell elongation and apical dominance?

Answer 6

Auxin

Question 7

Gibberellins are a group of plant hormones that play a role in:
a) Seed dormancy
b) Ethylene production
c) Stomatal closure
d) Root hair development

Answer 7

a) Seed dormancy

Question 8

Cytokinins can influence various aspects of plant growth and development, including cell division and ____ bud formation.

Answer 8

lateral

Question 9

What pigment molecule in plants is responsible for absorbing light and initiating phototropism (growth towards light)?

Answer 9

Photochrome

Question 10

Phytochrome exists in two forms: Pfr (red light absorbing) and Pr (far-red light absorbing). How does the differential absorption of these light forms influence plant growth?
a) Pfr promotes stem elongation, while Pr inhibits it.
b) Both Pfr and Pr promote stem elongation.
c) Pfr inhibits stem elongation, while Pr promotes it.
d) Light has no effect on stem elongation.

Answer 10

a) Pfr promotes stem elongation, while Pr inhibits it.

Question 11

The uneven distribution of auxin due to differential light exposure on opposite sides of a shoot is crucial for phototropic bending. The shaded side typically has a(n) ____ concentration of auxin, leading to increased cell elongation.

Answer 11

higher

Question 12

TF: Photoperiodism refers to the response of plants to the relative lengths of day and night, influencing flowering, dormancy, and other seasonal adaptations.

Answer 12

True

Question 13

Explain the concept of a critical daylength plant and how it differs from a long-day plant or a short-day plant in terms of flowering response.

Answer 13

Critical daylength plants flower when the daylength is either longer or shorter than a specific critical period. Long-day plants require a daylength exceeding the critical daylength to flower, while short-day plants flower when the daylength is shorter than the critical daylength.

Question 14

What is the name of the plant pigment molecule involved in the shade-avoidance response, where plants growing close together exhibit increased stem elongation?

Answer 14

Phytochrome

Question 15

The blue light receptor protein, phototropin, is involved in various plant responses, including:
a) Phototropism
b) Seed dormancy
c) Ethylene production
d) Fruit ripening

Answer 15

a) Phototropism

Question 16

Guard cells regulate the opening and closing of stomata, tiny pores on the leaf surface for gas exchange. What environmental factor can trigger stomatal closure?

Answer 16

Water stress (low water availability)

Question 17

What is the response of plants to gravity, with roots growing downward and shoots growing upward?

Answer 17

Gravitropism

Question 18

The uneven distribution of a plant hormone, auxin, within the root cap (tip) is essential for gravitropism. In roots, auxin accumulates on the ____ side, stimulating root growth in that direction.
a) Lower
b) Upper
c) Right
d) Left

Answer 18

a) Lower. Auxin accumulates on the lower side due to gravity, promoting root growth downward.

Question 19

TF: Plants can detect and respond to mechanical stress, such as windblown conditions, by thickening their cell walls and altering growth patterns for increased stability.

Answer 19

True

Question 20

How do plants use hydrotropism and chemotropism to their advantage for root growth and nutrient acquisition?

Answer 20

Hydrotropism allows roots to grow towards areas with higher water content, while chemotropism enables them to grow towards essential nutrients in the soil.

Question 21

Ethylene gas is a plant hormone involved in various processes, including fruit ripening and the triple response in seedlings. Briefly describe the triple response.

Answer 21

The triple response is a coordinated response by etiolated (light-grown) seedlings when exposed to darkness. It involves: 1) stem elongation, 2) apical hook weakening, and 3) inhibition of root elongation.

Question 22

Abscisic acid (ABA) is a plant hormone associated with:
a) Seed germination
b) Stem elongation
c) Phototropism
d) Fruit ripening

Answer 22

a) Seed germination

Question 23

Dormancy is a period of reduced metabolic activity in plants, often triggered by environmental cues like cold temperatures or short daylengths. What hormone plays a role in inducing dormancy in some plants?

Answer 23

Abscisic acid (ABA)

Question 24

TF: Plants can communicate with each other through chemical signals released into the environment. These signals can warn neighboring plants of herbivore attack or other stresses.

Answer 24

True e.g. volatile organic compounds released by damaged plants

Question 25

Describe the concept of systemic acquired resistance (SAR) in plants and how it contributes to their defense mechanisms.

Answer 25

When a plant is infected with a pathogen, it can activate SAR, a signaling pathway that enhances its defense response throughout the plant. This can make the plant more resistant to subsequent pathogen attacks.

Question 26

What internal signal molecule plays a crucial role in seed germination, breaking seed dormancy, and stimulating seedling growth?

Answer 26

Gibberellin

Question 27

The process by which a dormant seed undergoes imbibition of water and resumes growth is called:
a) Dormancy induction
b) Seed germination
c) Phototropism
d) Ethylene production

Answer 27

b) Seed germination

Question 28

TF: Abscission is the process by which plants shed leaves, fruits, or flowers, often in response to environmental stresses or developmental cues.

Answer 28

True

Question 29

Explain the role of ethylene gas in fruit ripening and the process of abscission.

Answer 29

Ethylene promotes fruit ripening by triggering changes in color, texture, and flavor. It can also stimulate abscission by weakening the attachment zone between an organ and the stem.

Question 30

What is the term for the movement of plant organs due to changes in turgor pressure within cells?

Answer 30

Nastic movements

Question 31

Examples of nastic movements in plants include:
a) Phototropism
b) thigmonastic movements
c) gravitropism
d) seed germination

Answer 31

b) thigmonastic movements

e.g. leaves folding in response to touch

Question 32

Chemical defenses in plants can include:
a) Secondary metabolites with toxic or deterrent properties
b) Only primary metabolites like sugars and starches
c) Water-soluble pigments
d) None of the above

Answer 32

a) Secondary metabolites with toxic or deterrent properties

Question 33

Plants can also defend themselves against herbivores by attracting ____, which are natural enemies of the herbivores. These beneficial predators or parasites can help control herbivore populations.

Answer 33

beneficial insects (e.g., ladybugs)

Question 34

Mutualistic relationships between plants and other organisms can be beneficial for both partners. For example, some plants have a symbiotic relationship with ____ fungi that assist with nutrient acquisition from the soil.

Answer 34

mycorrhizal

Question 35

Pollination is the transfer of pollen grains from the ____ to the ____ of a flowering plant. This is a crucial step in plant reproduction, often involving interactions with pollinators like bees or butterflies.

Answer 35

anther, stigma