Bio Plant Hormones

Front 1

How do plants increase their chance of survival by responding to changes in their environment?

Back 1

1) They sense direction of light & grow towards it, maximising light absorption for photosynthesis
2) They sense gravity, so their roots and shoots grow in the right direction
3) Climbing plants have a sense of touch, so they climb things to find and reach sunlight

Front 2

What responses do plants have that make them respond to predators?

Back 2

Produce substances that are toxic to cattle

Front 3

What are auxins?

Back 3

Plant hormones that control growth at the tip of shoots and roots.

Travels through the plant in solution

Front 4

Where are auxins produced?

Back 4

In the tips and diffuse backwards to stimulate the cell elongation process.

Front 5

What do auxins promote?

Back 5

Growth in the shoot, and inhibits growth in root.

Involved in growth responses of plants to light (phototropism) and gravity (geotropism)

Front 6

SHOOTS ARE POSITIVELY PHOTOTROPIC (grow towards light) How does it do this?

Back 6

1) When a shoot tip is exposed to light, it accumalates more auxin in the shady side than the side exposed to light.

2) Making cells elongate faster on the shaded side so the shoot bends towards the light?

Front 7

SHOOTS ARE NEGATIVELY GEOTROPIC (grow away from gravity)

Back 7

1) When a shoot is growing sideways, gravity produces an unequal distribution of auxin in the tip= more auxin on lower side.

2) Causing the lower side to grow faster, bending the shoot upwards.

Front 8

ROOTS ARE POSITIVELY GEOTROPIC (grow towards gravity)

Back 8

1) Root growing sideways, will have more auxin on the lower side.

2) But in a root, extra auxin inhibits growth. Cells on the top elongate faster, and the root bends downwards.

Front 9

Positive phototropism

Back 9

Growing towards light

SHOOT

Front 10

Negative phototropism

Back 10

Growing away from light

ROOT

Front 11

Positive geotropism

Back 11

Growing towards gravity

ROOT

Front 12

Negative geotropism

Back 12

Growing away from gravity

SHOOT

Front 13

Main stimuli affecting growth of shoot is?

Back 13

Sun

Front 14

Main stimuli affecting growth of root is?

Back 14

Deeper roots for water + minerals; gravity + nutrients.