B12 Tropic Response

Question 1

Geotropism

Answer 1

a response in which a plant grows towards or away from gravity

Question 2

Phototropism

Answer 2

a response in which a plant grows towards or away from the direction from which light is coming

Question 3

Tropism

Answer 3

a growth in response to a stimulus.

Question 4

Auxins

Answer 4

special plant hormones that respond to tropisms and stimuli. It is responsible for controlling the direction of growth of root tips and stem tips in response to different stimuli. It is made at the tips of stems and roots.

Question 5

Positive tropism

Answer 5

when the plant grows towards the stimulus

Question 6

Negative tropism

Answer 6

When the plant grows away from the stimulus

Question 7

Hydrotropism

Answer 7

a response to water/ moisture. When a plant grows towards or away from a source of moisture

Question 8

Thigmotropism

Answer 8

A response to touch. An example is when creepers will coil around other branches. `

Question 9

Geotropism in the root tip and shoot

Answer 9

Root tip- Positive tropism. Allows plant better chance of finding moisture
Shoot- Negative tropism. Allows plant better chance of finding light. The plant wants to break out of the soil and grow against gravity

Question 10

Phototropism in Stem tip and root tip

Answer 10

Stem tip- Positive tropism. Maximizes chances of leaves being in the light
Root tip- negative tropism. Makes the plant less likely to dry up

Question 11

Hydrotropism in root tip and shoot/ stem

Answer 11

Root tip- Positive tropism. Allows plant better chance of maximum water absorption
Shoot/ stem- Negative tropism. Allows plant to grow upwards away from soil moisture

Question 12

Thigmotropism in stem and creeper stems

Answer 12

Creepers- Positive tropism. Allows for better stability in climbing up towards light
Stem- Negative tropism. plant grows away from an obstruction/ obstacle

Question 13

How does an auxin cause growth?

Answer 13

The auxin causes the growth in a region just behind the shoot tip. Auxins move back from the shoot tip into the elongation/ growing zone and the shoot grows when stimulated by the auxin

Question 14

How is positive phototropism achieved?

Answer 14

The auxin is destroyed by the sunlight. The auxin therefore stimulates the growth of the cells on the dark side of the shoot. This uneven growth on one side leads to a bending of the shoot towards the side that the light is coming from.

Question 15

What can you conclude from covering a shoot tip in opaque aluminium foil?

Answer 15

Opaque means that bright light can’t get in. It shows that growth direction of shoots is dependent on light penetration, as the shoot doesn’t bend.

Question 16

What can you conclude from cutting a shoot tip off and replacing it by sticking it to a fully permeable agar jelly block?

Answer 16

It shows that the phototropism of the shoot is independent to the intact shoot structure, as the shoot bends towards the light

Question 17

What can you conclude from the shoot tips being cut off and replaced by sticking it to a non permeable sheet of plastic?

Answer 17

It shows that phototropism relies/relates to a substance which needs to be diffused through a permeable membrane, as the auxins cannot diffuse downwards from the shoot