Plant Response

Question 1

What is tropism?

Answer 1

Directional growth due to a stimulus

Question 2

What is Phototropism?

Answer 2

Growth towards light

Question 3

What is Geotropism?

Answer 3

Growth towards gravitational pull

Question 4

What is Chemotropism?

Answer 4

Growth towards chemicals.

eg. pollen tube growing towards ovary sac in plants for fertilisation

Question 5

What is Thigmotropism?

Answer 5

Growth towards a surface in contact.

Question 6

What are the plants response to herbivores?

Answer 6

Tannins
Alkaloids
Pheromones

Question 7

How do plants use Tannins?

Answer 7

Leaves : taste bad
Roots: prevent pathogen entry

phenolic compounds

Question 8

How do plants use Alkaloids?

Answer 8

Bitter

Derived from amino acids w/ nitrogen containing bases

Question 9

What are Pheromones?

Answer 9

Chemicals released that affect another’s behaviour or physiology.

Question 10

What is positive and negative tropic?

Answer 10

growth towards and away from the stimulus.

Question 11

What is a non-directional response?

Answer 11

Nastic response

Question 12

What are the plant hormones?

Answer 12

Abscisic acid
Cytokines
Ethene
Gibberellins
Auxins

Question 13

What does Abscisic acid do?

Answer 13

Inhibit seed germination and growth

stomatal closure due to low water availability.

Question 14

Auxins function

Answer 14

promote cell elongation
inhibit side shoot growth
prevent abscission ( leaf fall)

Question 15

Gibberellins

Answer 15

promote seed germination and growth of stem

Question 16

Function of ethene

Answer 16

fruit ripening

Question 17

Cytokinins function

Answer 17

Overrides Apical Dominance
Promote cell division + expansion
Delay senescence ( leaf aging)

Question 18

what is apical dominance?

Answer 18

Inhibition of lateral bud growth further down the shoot.

Question 19

What is the evidence for auxin’s role in apical dominance?

Answer 19

Auxin transporter inhibitor applied on plant, below apex

Lateral bud grew.

Question 20

What is the role of auxin in controlling plant growth?

Answer 20

Normal levels = inhibit growth in LB

Low levels = promote growth in LB

but the auxin levels and growth may have no affect on each other but a third variable is affecting them.

Question 21

Role of Abscisic acid in controlling plant growth

Answer 21

A growth inhibitor

High conc auxins in the shoot == High abscisic acid in LB

so remove auxins = low Abscisic acid in LB

=more growth

Question 22

Role of Cytokinins in controlling plant growth

Answer 22

Promote bud growth and overides apical dominance

Auxins act as sink
so cytokinins are concentrated in tip

remove auxin (tip) = even distribution
= plant grows evenly

Question 23

Experimental evidence for gibberellin’s role in stem elongation

Answer 23

Test gibberellic acid on dwarf plants which grew taller, suggesting GA is involved in stem elongation

Question 24

Which two experiments are important in investigating phototropism?

Answer 24

Boysen-Gensen and Darwin’s

Question 25

Why is water important in seed germination?

Answer 25

Stimulates embryo to release gibberellins which enable amylase production converting starch to glucose to use for respiration.

Question 26

How can gibberellins be used for plant breeding?

Answer 26

Induce seed production even in young plants so less time needed.