Plant responses

Question 1

why do plants respond to light?

Answer 1

To maximise light absorption for photosynthesis

Question 2

Why do plants respond to gravity?

Answer 2

So their roots and shoots grow in the right direction

Question 3

How do climbing plants respond to changes in environment?

Answer 3

they have a sense of touch

- So they can find things to climb and move towards the sun light.

Question 4

How do plants respond to herbivores?

Answer 4

By releasing toxic chemicals in response to being eaten

Question 5

what are some examples of chemicals plants release in response to being eaten by herbivores?

Answer 5

Alkaloids- bitter taste, noxious smells, poisonous characteristics that deter or kill herbivores.

Tannins- bitter taste
- tannins can even bind to the proteins in the gut of the herbivore who ate the plant, making the plant hard to digest. Deter herbivores from eating.

Question 6

What are pheromones that plants release?

Answer 6

Pheromones are signalling chemicals which produce a response in other organisms.

E.G: alarm pheromones are released into the air in response to herbivore grazing, This can cause nearby plants to detect these chemicals and start making chemical defences like tannins.

Question 7

Why is plants folding a good way to respond to being touched?

Answer 7

Signal spreads throughout the leaf causing it to fold up. A leaf of the “mimosa pudica” plant does this.

This folding protects the plant as it helps to knock off small insects eating the plant or deter animals from eating the plant.

Question 8

What is abiotic stress to a plant?

Answer 8

Anything that is harmful but NON living- like a drought or earthquake.

Question 9

How do carrots respond to extreme cold?

Answer 9

Carrots produce anti freeze proteins, these proteins bind to ice crystals and lower the temperature at which the water freezes

Question 10

What is a tropism?

Answer 10

The response of a plant to a directional stimulus.

positive tropism- grows towards stimulus
negative tropism- grows away from stimulus.

Question 11

what is phototropism?

Answer 11

Growth of a plant in response to light

shoots are positively phototropic as they grow towards light

roots are negatively phototropic as they grow away from light

Question 12

What is geotropism?

Answer 12

The growth of a plant in response to gravity

Roots are positively geotropic and grow downwards
Shoots are negatively geotropic and grow upwards.

Question 13

What is thigmotropism?

Answer 13

Plant growth in response to object

Question 14

What is thermotropism?

Answer 14

Plant growth in response to temperature.

Question 15

What is hydrotropism?

Answer 15

Plant growth in response to water.

• Roots are positively hydrotropic

Question 16

What are growth hormones in plants?

Answer 16

chemicals that speed up or slow down plant growth.

Question 17

Where are growing hormones produced in a plant?

Answer 17

They are produced in the tips of shoots and leaves.

Question 18

Which hormone promotes stem elongation auxins or gibberelins?

Answer 18

Gibberellins

Question 19

what does the hormone gibberellin do?

Answer 19

They stimulate:

seed germination,
stem elongation
side shoot formation and flowering

Question 20

What does the hormone auxin do?

Answer 20

Stimulates cell elongation ( growth of shoots)

cell elongation- is where the cell walls become loose and stretchy so the cells get longer.

Question 21

What plant hormone in high concentration can inhibit growth in the roots?

Answer 21

Auxins

Question 22

Is IAA auxin or gibberelin?

Answer 22

Auxin

(Indoleacetic acid)

It controls tropisms
and moves by diffusion and active transport over short distances
and moves via the phloem for long distances

Question 23

What does uneven distribution of IAA mean

Answer 23

uneven growth of plant.

Question 24

For phototropism how does IAA move?

Answer 24

Moves to the shaded parts of the shoots and roots, so there is uneven growth

shoots: IAA moves to the tip of the shoot, cells elongate and the shoot bends towards the light

Roots: IAA moves to the roots, growth is inhibited and root bends away from the light

Question 25

For geotropism how does IAA move?

Answer 25

Moves to the underside of shoots and roots, so there is uneven growth.

shoots: IAA moves towards the underside of the shoot tip, cells elongate, so the shoot grows upwards.
roots: IAA moves towards the roots, growth is inhibited so the root grows downwards.