Tropisms

Question 1

what is the stimulus

Answer 1

change in the environment

Question 2

what is the response

Answer 2

• caused by a stimulus

- which triggers a change or reaction (effect)

Question 3

what is tropism

Answer 3

the growth in response to a stimulus

Question 4

what is positive tropism

Answer 4

the growth towards a stimulus

Question 5

what is negative tropism

Answer 5

the growth away from a stimulus

Question 6

what are plant roots in terms of tropism and why

Answer 6

• negatively phototropic and positively gravitropic
• because they grow away from light and towards the ground as they obey gravity
• photo = light and negatively = away
• gravi = ground and positively = towards
• they do this to grow underground.

Question 7

what do plants use in order to respond to a stimulus

Answer 7

hormones

Question 8

what does the hormone auxin cause

Answer 8

elongation and inhibition of cells

Question 9

how and why do plants curve towards sunlight

Answer 9

• when theres a shaded part of the plant
• the auxins go to that shaded side and elongate the cells
• this causes the plant to curve and face towards the light so it can receive more sunlight

Question 10

where are auxins produced

Answer 10

• at the tip of the shoot

- they move to the shaded area form there

Question 11

what do the auxins in roots do and why

Answer 11

• the auxins in roots inhibit elongation
• this is because when they go to a shaded area which will be the bottom of the root
• you want the root to grow downwards
• so it halts the growth of cells at the bottom in order to allow the cells at the top to grow over it and cause the root to droop downward

Question 12

what is it called when auxins inhibit the growth of cells on the shaded area of the root, causing them to grow downwards

Answer 12

gravitropism

Question 13

what is phototropism

Answer 13

growth of an organism in response to light

Question 14

what is geotropism

Answer 14

growth of an organism in response to gravity

Question 15

why are shoots actually negatively gravitropic in terms of the effect of gravity

Answer 15

• when a shoot is growing sideways
• gravity produces an unequal distribution of auxin in the tip
• with more auxins on the lower side, this causes the lower side to grow faster
• which leads to the bending of the shoot upwards

Question 16

why are shoots positively gravitropic in terms of the effect of gravity

Answer 16

• the root is growing sideways so will have more auxins on its lower side due to gravity acting downwards
• but in a root the auxins inhibit cell growth
• so they cells on the top elongate faster
• and the root bends downwards