SB6f

Question 1

What is a Stimulus?

Answer 1

A stimulus is a change in the environment that causes a response in an organism

Question 2

What are the 3 stimuli that plants respond to?

Answer 2

 Water
 Light
 Gravity

Question 3

What is Tropism

Answer 3

Tropism is when the stimulus is coming from one direction and the
plant is responding to it.

Question 4

What are the 2 types of Tropism?

Answer 4

Negative tropism i.e. away from the stimulus.
Positive tropism i.e. towards the stimulus.

Question 5

What is the name given to the Tropism of light?

Answer 5

phototropism

Question 6

What is the name given to the Tropism of water?

Answer 6

hydrotropism

Question 7

What is the name given to the Tropism of gravity?

Answer 7

geotropism

Question 8

How do plants Respond to gravity?

Answer 8

Plants grow roots in soil to get water and mineral and to anchor the
plant in soil for support.

Question 9

How do plants Respond to light?

Answer 9

Plants grow shoot towards light taking advantage of the brightest
light source for more photosynthesis.

Question 10

How do plants Respond to water?

Answer 10

Plant roots grow towards water to get more so they can do more
photosynthesis.

Question 11

What is a hormone?

Answer 11

Hormone is a chemical that is produced in an organ, after
a stimulus is detected, in order to have an effect
somewhere else over the long run.

Question 12

What are Auxins? where are they produced?

Answer 12

 Auxins are the growth hormone of plants.
 They are produced and released in the stem and roots of plants.

Question 13

What are the Effects of auxins on cells?

Answer 13

 Sun is detected as a stimulus for the plant.

 Auxin molecules at the tip, move to the side away from the sun
(shaded area).

 Auxin makes cell walls of plant cells (cellulose) more flexible/elastic.
 Plant cells can now elongate.

 The shoot bends towards the sun.

 The plant can now get more sunlight to maximise the rate of
photosynthesis.

Question 14

What effect do auxins have on roots?

Answer 14

In roots, auxins STOP elongation, so the side with the highest auxin
concentration grows less.
Gravity pulls the auxins downwards, so the lower side has more
auxins.

Question 15

Name all 3 plant hormones.

Answer 15

Auxins

Gibberellins

Ethene

Question 16

What does Gibberellins do?

Answer 16

Gibberellins are plant hormones that cause seeds to germinate (start growing) to grow shoots and roots.

Question 17

What does Ethene do?

Answer 17

Ethene gas is a plant hormone that causes fruit to ripen.