8.1.7 - The Effects Of IAA

Question 1

How To Plants Increase Their Chances Of Survival?
(2 Points)

Answer 1

~ Grow towards the light, to maximise the rate of photosynthesis.

~ Produce harmful of foul-tasting chemicals, to reduce the likelihood of being eaten.

Question 2

What Is Tropism?
(2 Points)

Answer 2

~ Response of a plant to a directional stimulus.

~ There is phototropism and geotropism.

Question 3

What Is Phototropism?
(3 Points)

Answer 3

~ Growth response to light.

~ Positive phototropism -> growth towards light.

~ Negative phototropism -> growth away from the light.

Question 4

What Is Geotropism?
(3 Points)

Answer 4

~ Growth response to gravity.

~ Positive geotropism -> growth downwards.

~ Negative geotropism -> growth upwards.

Question 5

Describe Growth Factors
(3 Points)

Answer 5

~ Act like hormones.

~ Produced in the growing regions of a plant, and move to where they are needed.

~ E.g. Auxin / IAA.

Question 6

Describe IAA / Auxin
(4 Points)

Answer 6

~ Produced in the tips and shoots in plants.

~ When it enters the nucleus, it is able to regulate transcription, to effect cell growth.

~ Transported by diffusion and active transport, aswell as via the phloem for long distances.

~ Causing uneven growth, due to an unequal distribution of IAA.

Question 7

Describe IAAs Role In Phototropism
(3 Points)

Answer 7

~ IAA moves to the shaded side, when light shines.

~ An IAA gradient is established.

~ Higher concentration of auxin on the shaded side, causing a faster cell elongation, causing the shoot to bend towards the light.

Question 8

Describe IAAs Role In Geotropism
(3 Points)

Answer 8

~ IAA moves towards the lower side of the plant roots.

~ Resulting in a higher concentration of auxin on the lower side.

~ Lower side grows at a slower rate then the upper side of the root, causing the root to bend down.