5.4 Plant Responses

Question 1

Plants respond to what changes in their environment?

Answer 1

Lack of water
Light
Gravity

Question 2

What are some limitations of plants?

Answer 2

Don’t have a nervous system

Rely on hormones which are much slower

Question 3

(Hormones) what role do auxins play in plants?

Answer 3

Control cell elongation
Prevent abscission
Maintain apical dominance
Tropisms
Stimulate ethene release

Question 4

(Hormones) what is the role of gibberellins in plants?

Answer 4

Cause stem elongation
Pollen tube growth
Mobilisation of food stores in germination

Question 5

(Hormones) what is the role of ethene in plants?

Answer 5

Causes ripening

Promoted abscission

Question 6

(Hormones) what is the role of ABA in the plant?

Answer 6

Maintains dormancy of deeds and buds

Stimulates protective responses such as antifreeze and stomatal closing

Question 7

(Gibberellins in germination) for a plant to start growing it must do what?

Answer 7

Germinate

Question 8

(Gibberellins in germination) 1. How is the embryo activated?

Answer 8

Seed absorbs water

Question 9

(Gibberellins in germination) 2. The seed begins producing what?

Answer 9

Gibberellins

Question 10

(Gibberellins in germination) 3. Gibberellins stimulate production of enzymes that do what?

Answer 10

Breakdown food stores

Question 11

(Gibberellins in germination) 4. The embryo uses the food stores to make what?

Answer 11

Building materials to break through the seed coat

Question 12

(Gibberellins in germination) 5. Gibberellins switch in genes coding for what?

Answer 12

Amylase and protease

Question 13

(Gibberellins in germination) 6. ABA acts with gibberellins to determine what?

Answer 13

When the seed will terminate

Question 14

What are auxins and where are they made?

Answer 14

Growth stimulants in plants

Made at tips of roots and shoots

Question 15

(Auxins) what do auxins do in plants?

Answer 15

Stimulate growth of social shoot
Suppress lateral shoot growth
Promote root growth

Question 16

(Auxins - apical shoot growth) 1. Auxin is synthesised where?

Answer 16

Meristems

Question 17

(Auxins - apical shoot growth) 2. Auxins diffuse away from where?

Answer 17

Tip

Question 18

(Auxins - apical shoot growth) 3. Auxins bind to what?

Answer 18

Receptor sites on cells

Question 19

(Auxins - apical shoot growth) 4. vacuoles form web what develops?

Answer 19

Low ph

Question 20

(Auxins - apical shoot growth) 5. Low pH does what to cell walls?

Answer 20

Keeps them flexible allowing cells to expand as they absorb water
Vacuoles get bigger

Question 21

(Auxins - apical shoot growth) 6. A large central vacuole forms, cell walls become rigid and no more what is possible?

Answer 21

Cell elongation as auxins are destroyed

Question 22

(Auxins - apical dominance) growth in the main apical shoot is stimulated by what?

Answer 22

Auxin produced at tip

Question 23

(Auxins - apical shoot growth) as the auxin moves down the stem what happens?

Answer 23

Lateral shoots are inhibited

Question 24

(Auxins - apical shoot growth) further down the stem auxin concentration is lower making what?

Answer 24

Lateral shoots grow more strongly

Question 25

(Auxins - apical shoot growth) what happens to the lateral shoots if the main apical shoot is removed?

Answer 25

They grow as they are no longer inhibited

Question 26

(Auxins - root growth) up to a certain concentration the more auxin that reached the roots the more they what?

Answer 26

Grow

Question 27

(Auxins - root growth) high concentrations of auxins do what to the roots?

Answer 27

Inhibit their growth

Question 28

(Auxins - root growth) if the apical shoot is removed the auxin reaching roots is what?

Answer 28

Reduced | Slowing and stopping root growth

Question 29

(Gibberellins) what are gibberellins important in?

Answer 29

Stem elongation | Germination of seeds

Question 30

(Gibberellins) gibberellins affect the length of what?

Answer 30

Internodes

Question 31

(Gibberellins) how were they discovered?

Answer 31

Fungus infecting rice plants producing gibberellins making them grow long and thin

Question 32

(Gibberellins) modified plants have been produced to produce little gibberellins and remain short, this is beneficial as..

Answer 32

They are less damaged by weather

Question 33

What is synergism?

Answer 33

Different hormones working together complimenting each other

Question 34

What is antagonism?

Answer 34

Hormones having opposite effects e.g. One promoting growth one preventing it