Tropisms

Question 1

What exhibits positive phototropism?
Plant roots goes away from light and towards water and gravity, what are these described as?
What are the survival reasons for these?

Answer 1

Plant shoots growing towards light
Negative phototropism, positive hydrotropism,positive geotropism
Towards light photosynthesis
Anchor plant
Water for osmosis of water for photosynthesis

Question 2

Plant growth factors 
  What are they also known as?
  What do they affect? What 3 ways do they do this?
  What are they made by?
  What do some affect?

Answer 2

Plant hormones 
Plant growth 
Elongation,differentiation,division
Cells located throughout the plant
Cell they are released by

Question 3

IAA 
  What type of hormone is it?
  What does it do to cells?
  What's does it do to shoots what does it do in roots?
  Where is it made?

Answer 3

Auxin
Elongates
Stimulates, inhibits
Shoot tip

Question 4

Control of tropisms by IAA

A young shoot will bend towards light. Explain how light causes this.(6)

Answer 4

Cell at tip of shoot produces IAA
Moves down plant diffused to all cells
Light hits moves to shaded side
Greater IAA build up on one shaded side causes cells to elongate
Grow faster and plant bends towards light

Question 5

What happens if you remove tip of shoot?

Answer 5

IAA won’t be made in shoot

Shoot won’t grow

Question 6

IAA and Gravity
Describe events for negative geotropism of shoot(2)
Describe events for positive geotropism of roots(2)

Answer 6

IAA falls to lower side of plant
Causes cells to grow faster than upper side so bends upwards

IAA falls to lower side of plant
Causes cells to grow slower so upper side grows faster bends downwards

Question 7

Describe IAA and positive hydrotropism

Answer 7

IAA moves to side closer to water
Causes cells to grow slower
Root bends towards water

Question 8

What does gelatin allow?

Answer 8

Chemicals to pass through

Question 9

Auxin 
  What does it loosen?
  What does this stimulate?
  What does this decrease? What does this activate?
  What does this cause?

What does auxin increase?
What is this?

Answer 9

Cellulose fibres
Transport of hydrogen ions into cell wall
pH
Proteins which alter hbonding that link cellulose fibres together
Elongation of cell

Plasticity of cell wall
Adaptability of organism to changes in its environment or differences in various habitats

Question 10

What are tropisms?

What is it towards something and away?

Answer 10

Growth movement of a plant in response to stimulus

Positive tropism and negative tropism