Plant Responses

Question 1

What is a stimulus in plants?

Answer 1

A stimulus is something that causes a response in an organism.

Question 2

What is the most common response by plants to stimuli?

Answer 2

The most common response by plants to stimuli is a growth response.

Question 3

Name three stimuli that plants respond to.

Answer 3

Light (phototropism), gravity (geotropism), and water (hydrotropism).

Question 4

What is a tropism?

Answer 4

A tropism is a change in the growth of a plant in response to an external stimulus.

Question 5

What is positive tropism?

Answer 5

Positive tropism is when a plant’s growth is towards a stimulus.

Question 6

What is negative tropism?

Answer 6

Negative tropism is when a plant’s growth is away from a stimulus.

Question 7

What are external factors that regulate plant growth?

Answer 7

External factors include light intensity, day length, gravity, and temperature.

Question 8

What are internal factors that regulate plant growth?

Answer 8

Internal factors include chemicals called growth regulators, which are produced in meristematic regions.

Question 9

What is a growth regulator in plants?

Answer 9

A growth regulator is a chemical that controls the growth of a plant.

Question 10

Where are growth regulators produced in a plant?

Answer 10

Growth regulators are produced in meristematic regions like root tips and shoot tips.

Question 11

What are auxins?

Answer 11

Auxins are a group of growth regulators that promote growth, such as Indoleacetic Acid (IAA).

Question 12

Name two production sites of auxins.

Answer 12

Auxins are produced in shoot tips and developing seeds.

Question 13

What role do auxins play in plant growth?

Answer 13

Auxins promote stem and root elongation, fruit development, and cell differentiation, and they regulate phototropism and geotropism.

Question 14

What is apical dominance?

Answer 14

Apical dominance is when the auxin produced in the apical tip inhibits lateral growth, leading to dominant upward growth.

Question 15

What is apical dominance?

Answer 15

Apical dominance is when the auxin produced in the apical tip inhibits lateral growth, leading to dominant upward growth.

Question 16

What effect does Indoleacetic Acid (IAA) have on roots and shoots?

Answer 16

Low concentrations of IAA cause root growth, while high concentrations promote shoot growth and inhibit root growth.

Question 17

What is the function of ethene in plants?

Answer 17

Ethene is a gas that causes fruit ripening, leaf fall, and is involved in the aging of plants.

Question 18

What is the role of abscisic acid in plants?

Answer 18

Abscisic acid responds to harmful conditions by triggering dormancy in buds and seeds, inhibiting germination, and causing stomata to close during dry conditions.

Question 19

Where is auxin (I.A.A.) produced in plants, and what does it do?

Answer 19

Auxin (I.A.A.) is produced in the meristem region at the tip of the stem and travels down the stem to stimulate growth in different areas.

Question 20

How does auxin (I.A.A.) cause a plant to bend towards light in phototropism?

Answer 20

When exposed to light on one side, auxin diffuses down the shaded side of the stem, increasing its concentration there. This causes the shaded side to elongate and grow more than the sunny side, bending the stem towards the light.

Question 21

What is phototropism?

Answer 21

Phototropism is the bending of a plant stem towards light due to the uneven distribution of auxin (I.A.A.), which causes more growth on the shaded side.

Question 22

How is ethene used commercially in agriculture?

Answer 22

Ethene is used to ripen bananas or other fruit. Bananas are picked green, and ethene is used to stimulate ripening just before distribution.

Question 23

What is the purpose of rooting powders in plant propagation?

Answer 23

Rooting powders contain synthetic auxins like NAA, which stimulate rapid root formation on stem cuttings.

Question 24

Why do plants need adaptations for protection?

Answer 24

Plants need to protect themselves against adverse external environments, such as hot conditions, infection by microorganisms, and herbivores.

Question 25

What are structural/anatomical adaptations for plant protection?

Answer 25

Examples include tough bark, waxy or thick cuticles, stoma closing in certain conditions, and the formation of stings or thorns to prevent herbivore consumption and reduce water loss.

Question 26

How do guard cells help plants conserve water?

Answer 26

Guard cells change shape when they lose water, causing the stomata to close, which reduces water loss.

Question 27

What are chemical adaptations in plants for protection?

Answer 27

Plants produce heat shock proteins to protect enzymes at high temperatures, and phytoalexins in response to infections, which can attack microorganisms and stimulate other plants to respond.

Question 28

What are phytoalexins, and what do they do?

Answer 28

Phytoalexins are stress proteins produced by plants in response to microorganism infection. They attack microorganism cell walls and stimulate other plants to defend themselves.