Plant Responses 2.0

Question 1

What is a stimulus?

Answer 1

Anything that causes a reaction in an organism or any of its parts.

Question 2

What is a response?

Answer 2

Activity of a cell or organism that happens as a result of a stimulus.

Question 3

What are external factors that cause responses?

Answer 3

Light, day length, gravity, temperature.

Question 4

What are internal factors that cause responses?

Answer 4

Plants produce chemicals called ‘Growth Regulators’ in the meristematic regions of the plant: Shoot & root tip.

Question 5

What is tropism?

Answer 5

Change in the growth of a plant due to external stimulus.

Question 6

What is positive tropism?

Answer 6

Occurs when the growth is towards the stimulus.

Question 7

What is negative tropism?

Answer 7

Occurs when growth is away from the stimulus.

Question 8

What is an advantage of tropism?

Answer 8

Plants can achieve more favourable conditions for growth.

Question 9

What are the types of tropism?

Answer 9

Phototropism, geotropism, thigmotropism, hydrotropism, and chemotropism.

Question 10

What is phototropism?

Answer 10

Changes in growth of a plant in response to light.

Question 11

What is positive phototropism?

Answer 11

Stems grow towards light.

Question 12

What is negative phototropism?

Answer 12

Roots grow away from light.

Question 13

What is an advantage of phototropism?

Answer 13

Increased photosynthesis.

Question 14

What is geotropism?

Answer 14

Change in growth of a plant in response to gravity.

Question 15

What is positive geotropism?

Answer 15

Roots grow with gravity.

Question 16

What is negative geotropism?

Answer 16

Stem grows away from the direction of gravity.

Question 17

What is thigmotropism?

Answer 17

Change in growth of a plant in response to touch.

Question 18

What is positive thigmotropism?

Answer 18

Plants that have tendrils grow around supporting structures.

Question 19

What is hydrotropism?

Answer 19

Change in growth of a plant in response to water.

Question 20

What is positive hydrotropism?

Answer 20

Roots grow towards water.

Question 21

What are growth regulators transported in?

Answer 21

Transported in vascular tissue.

Question 22

What is chemotropism?

Answer 22

Change in growth of plant in response to chemicals.

Question 23

What is positive chemotropism?

Answer 23

Roots grow towards minerals in soil. Pollen tube grows towards chemicals in ovule.

Question 24

What is negative chemotropism?

Answer 24

Most roots will not grow towards acids or heavy metals (Lead & zinc) in soil.

Question 25

What are growth regulators?

Answer 25

Chemicals that control the growth of a plant.

Question 26

What are the functions of growth regulators?

Answer 26

Produced in small amounts & transported to another part of the plant to have an effect (Like hormones in us). Can be promoters or inhibitors.

Question 27

Define auxin.

Answer 27

A plant growth regulator.

Question 28

What are the uses of growth regulators in agri/horticulture?

Answer 28

Fruit ripening, seedless fruit.

Question 29

What are growth promoters?

Answer 29

Chemicals that cause increased growth in plants.

Question 30

What is an example of a growth promoter?

Answer 30

Auxins (IAA - Indole Acetic acid).

Question 31

Where are auxins made?

Answer 31

Made in meristematic tissue in tips & shoots.

Question 32

What are the functions of auxins?

Answer 32

Stimulates stem elongation, stimulates root growth, develops fruit, causes phototropism.

Question 33

What is the inhibitory function of auxins?

Answer 33

Slows mitosis.

Question 34

What are the types of auxins?

Answer 34

IAA, Ethene & Acetic acid.

Question 35

What is apical dominance?

Answer 35

If apical bud in stem is present, auxin is produced in tip, preventing lateral buds & side branching.

Question 36

What happens if the apical bud is removed?

Answer 36

Lateral bud can occur.

Question 37

How does concentration of IAA affect growth?

Answer 37

Low IAA concentration = Root growth. High IAA concentration = Shoot growth.

Question 38

What is the mechanism of phototropism?

Answer 38

IAA produced in meristem of stem; when exposed to light, IAA diffuses down the shaded side, causing uneven elongation and bending towards light.

Question 39

What are growth inhibitors?

Answer 39

Chemical that causes slowed growth in plants.

Question 40

What is an example of a growth inhibitor?

Answer 40

Ethene Gas.

Question 41

What are the functions of ethene?

Answer 41

Ripens fruit, causes fruit colour to form, stimulates more ethene production.

Question 42

What is the commercial use of ethene?

Answer 42

Green bananas picked from trees and transported across the world are exposed to ethene on arrival & allowed to ripen.

Question 43

What is abscisic acid?

Answer 43

Produced in leaves, stems & root caps.

Question 44

What are the functions of abscisic acid?

Answer 44

Helps plants withstand harsh conditions, causes stomata to close in dry conditions.

Question 45

What are commercially prepared growth regulators?

Answer 45

Ethene, root powder - Contains growth regulator NAA.

Question 46

What are anatomical protective adaptations/features of plants?

Answer 46

Thorns, stinging hairs, bark (prevents pathogen entry + water loss), stomata shrivel to close if there is a shortage of water.

Question 47

What are chemical protective adaptations/features of plants?

Answer 47

Formation of heat shock proteins to help enzymes maintain their shape in temperatures above 40 degrees, production of phytoalexins: Stress proteins.

Question 48

What are adverse external environments?

Answer 48

Surroundings that are harmful to an organism.