chemical coordination in plants

Question 1

what is a tropism

Answer 1

Tropism = the plant’s movement/response to external stimuli

Question 2

what are the 2 types of tropisms

Answer 2

Phototropism
Geotropism (Gravitropism)

Question 3

what is a phototropism

Answer 3

Phototropism - Photo = light = The directional movement of a (part of a) plant in response to light

Question 4

what is a geotropism

Answer 4

Geotropism (Gravitropism) - Geo=Earth/Gravi=Gravity = the directional movement of a (part of a) plant in response to gravity

Question 5

what is a positive tropism

Answer 5

Positive tropism = the plant’s growth response is towards the direction of the stimulus

Question 6

what is a negative tropism

Answer 6

Negative tropism = the plant’s growth response away from the direction of the stimulus

Question 7

what tropism if the shoot is moving towards the light upwards

Answer 7

If a shoot is moving upwards towards the light that is a positive phototropism, and negative geotropism

Question 8

what tropism will occur when there is unidirectional light

Answer 8

When there is unidirectional light (light from one direction), the shoot exhibits strong positive phototropism

Question 9

what tropism will occur when there is uniform light

Answer 9

However, when there is uniform light (the light is even from all directions), or darkness, the shoot exhibits negative geotropism

Question 10

what tropism do roots have

Answer 10

Roots have a positive geotropic response meaning they grow towards the direction of gravity

Question 11

how do roots respond to light

Answer 11

SOME plant roots have shown a negative phototropic response, but some/most plants have no response to light

Question 12

what are photoreceptors

Answer 12

Photoreceptors detect the presence of light

Question 13

what is auxin and its function

Answer 13

Auxin is a hormone that stimulates cell elongation along the side that is not receiving light
This causes the shoot/plant to bend towards the light

Question 14

what is a clinostat

Answer 14

Clinostat = apparatus with an electric motor that spins very slowly

Question 15

how do you use a clinostat to detect the effects of gravity and geotropism

Answer 15

You attach germinating seeds (like cotton) to the disc - the turning done by the clinostat eliminates any effect of gravity on the seeds, and so negates any geotropism that could happen
So due to this, the roots grow horizontal to the ground, however when the motor is stopped, it grows down in the direction of gravity