Plant hormones

Question 1

Meristems

Answer 1

Are a region of cells capable of mitosis division and indeterminate growth in plant

Question 2

Primary Growth

1. Occurs
2. Effect

Answer 2

1. Occurs in the apical meristem of the buds and root tups

2. Increases the length of a plant

Question 3

Secondary growth

1. Occurs
2. Effect

Answer 3

1. Occurs in the lateral meristem in the stem

2. Increases plant girth

Question 4

Growth Promoters

Answer 4

• Auxins
• Gibberellins
• Cytokinins

Question 5

Growth inhibitors

Answer 5

• Ethylene gas

- Abscisic acid

Question 6

Auxins roles

Answer 6

• plant growth
• flowering
• fruit development

Auxins stimulate genes in cells associated with plant growth that promote cell elongation ad increasing the rate of cell division

Question 7

Tropisms

Answer 7

Are the growth of a plant toward or away from a stimulus.
Tropisms involve cell elongation or suppression of cell elongation on one side of a plant, causing the plant to grow in particular direction

Question 8

1. Phototropism

Answer 8

1. In response to light: If the tip is exposed to light on one side, light receptors (Phototropism) trigger the redistribution of auxin to the dark side of the plant, which prompts that side to elongate and the tip bends towards the light

Question 9

Where are Auxins produced from?

Answer 9

From the tip of a shoot or root

Question 10

Role of auxin effluux pumps

Answer 10

Set up concentration gradients within tissues - changing the distribution of auxins within the plant

These pumps can control the direction of plant growth by determining which regions of plant tissue have high auxin levels

Auxin effluent pumps can change position within the membrane and be activated by various factors

Question 11

How does the cell wall become more flexible to change direction on growth?

Answer 11

1. Auxin activates a proton pump which causes the secretion of H+ ions into the cell wall
2. The resultant decrease in pH causes cellulose fibres within the cell wall to loosen
3. Additionally, auxin up-regulates expression of expansions, which similarly increase the elasticity of the cell wall
4. With the cell wall now more flexible, an influx of water (to be stored in the vacuole) causes the cell to increase in size

Question 12

1. Gravitropism

2. Thigmotropism

Answer 12

1. In response to gravity: Auxin will accumulate on the lower side of the plant in response to the force of gravity
2. In response to touch

Question 13

How is auxins mechanism of action different in shoots compared to roots?

Answer 13

1. In shoots, auxins are more concentrated on the lower side of the stem, causing the cells there to elongate.
2. In roots, auxin concentration on the lower side of the root suppresses cell elongation

Question 14

Apical Meristems

Answer 14

Give rise to primary growth and occurs at the tips of the roots and shoots