Chemical Coordination in plants

Question 1

What is tropism?

Answer 1

The growth response of a plant to a directional stimuli

Question 2

What are examples of directional stimuli?

Answer 2

Light and gravity as they act in a particular direction

Question 3

What is growth towards stimulus?

Answer 3

Positive tropism

Question 4

What is growth away from stimulus?

Answer 4

Negative tropism

Question 5

What is light in one direction called?

Answer 5

Uni-directional

Question 6

What is light that shines on the plant evenly from every direction called?

Answer 6

Uniform light

Question 7

What is the result of phototropism? (light)

Answer 7

• Shoots: positive as the shoots grow towards the light source
• Roots: negative, most roots don’t respond but if they do they grow away from the light source

Question 8

What is the result of geotropism (gravity)

Answer 8

• Shoots: negative as the shoots grow away from the direction of gravity
• Roots: positive as the roots grow towards the direction of gravity

Question 9

What is the result of hydrotropism (water)

Answer 9

• Shoots: none

- Roots: positive, some species may grow towards water however only a few

Question 10

What are auxins?

Answer 10

Plant growth hormones

Question 11

Describe the response to light

Answer 11

1. Auxins are released from the tip of the plant
2. They travel along the part of the plant which is NOT exposed to the sun/light
3. They initiate growth on that side causing the plant to bend towards the light

Question 12

Describe what happens with the auxins in geotropism?

Answer 12

• Auxins accumulate on the lower side of the shoot and STIMULATE growth, causing the shoot to bend upwards
• Auxins accumulate on the lower side of the root INHIBITING growth and causing the root to bend downwards
• The receptors in the root and shoots interpret the auxins differently which causes them to grow in different directions

Question 13

Do plants respond to stimuli?

Answer 13

Yes