5.1.5 Plant hormones

Question 1

In plants, hormones are transported by:

Answer 1

• Active transport
• Diffusion
• Mass flow (in phloem or xylem)

Question 2

Hormones affect processes of:

Answer 2

• Cell division
• Cell elongation
• Cell differentiation

Question 3

Effect of auxins

Answer 3

• Control cell elongation
• Prevent abscission
• Maintains apical dominance
• Involved in tropisms
• Stimulates release of ethene
• Involved in fruit ripening

Question 4

Effect of gibberellin

Answer 4

• Causes stem elongation
• Trigger mobilisation of food stores in seed at germination
• Stimulation of pollen tube growth in fertilisation

Question 5

Effect of ethene

Answer 5

• Causes fruit ripening

* Promotes abscission in deciduous trees

Question 6

Effect of ABA (abscisic acid)

Answer 6

• Maintains dormancy of seeds and buds
• Stimulates cold protective responses (e.g. antifreeze production)
• Stimulates stomatal closing

Question 7

Synergism

Answer 7

substances working together –> greater response than when hormones work alone

Question 8

Antagonism

Answer 8

substances have opposite effects; the balance between them determine the response

Question 9

Steps in seed germination

Answer 9

1) Seed absorbs water ⟶ embryo is activated and begins to produce gibberellins
2) Gibberellins stimulate production of enzymes to break down food stores in seed

Question 10

Monocots (seeds)

Answer 10

• Have only 1 seed leaf inside the seed coat

often because endosperm to feed new plant is not inside seed leaf

Question 11

Dicots (seeds)

Answer 11

• Have 2 seed leaves inside the seed coat

usually rounded and fat because they contain endosperm to feed embryo plant

Question 12

Role of gibberellins in seed germination

Answer 12

• Cause synthesis of amylase in seed
⟶ Amylase breaks down starch into glucose for respiration
⟶ Respiration provides energy for growth
⟶ Enabling seed germination

Question 13

Food store in dicot seeds?

Answer 13

Cotyledons

Question 14

Food store in monocot seeds?

Answer 14

Endosperm

Question 15

Endosperm:

Answer 15

the food store into monocot seeds.

Question 16

Cotyledon:

Answer 16

the food store in dicot seeds.

Question 17

What are food stores in seeds used for?

Answer 17

• To produce ATP for building materials

⟶ Allows growth and breaking out of seed

Question 18

Testa

Answer 18

Seed coat

Question 19

Seed coat

Answer 19

Testa

Question 20

Where does growth occur in plants?

Answer 20

Meristems ONLY

Question 21

Away from meristems, how can a plant become bigger?

Answer 21

The cell can elongate (not divide)

Question 22

Apical meristems are where?

Answer 22

at tips of roots and shoots

Question 23

Lateral bud meristems are where?

Answer 23

in buds, can give rise to side shoots