Coordination and response in plants

Question 1

Phototropism

Answer 1

growth response of a plant in response to light

Question 2

Positive phototropism

Answer 2

grows towards source of light ; shoot

Question 3

Negative phototropism

Answer 3

grows away from source of light ; roots

Question 4

Importance of phototropism

Answer 4

causes stems of plants to grow towards light source causing the leaves to also grow towards the light source ; allowing maximum absorption of light for photosynthesis

Question 5

Gravitropism / geotropism

Answer 5

growth response of a plant in response to gravity

Question 6

Positive gravitropism

Answer 6

grow in direction of force of gravity, downwards ; roots

Question 7

Negative gravitropism

Answer 7

grow against force of gravity, upwards ; shoots

Question 8

Importance of gravitropism

Answer 8

when roots grow downwards, towards gravity, it helps anchor the plant and allows it to obtain water & mineral ions from the soil

Question 9

Auxin

Answer 9

growth hormone produced by plants
- made in tips of growing stem & roots
- controls growth of plants by promoting cell elongation

Question 10

Apical meristems

Answer 10

tips of growing stem & root

Question 11

High concentration of auxin response

Answer 11

• promotes more growth in stems
• reduces growth in roots

Question 12

Auxin in phototropism

Answer 12

• caused by unequal distribution of auxin
• auxin diffuses to the darker side of the stem when light is shone on it
• causes growth on the illuminated side ; stem bends & grows towards the source of light

Question 13

Auxin in gravitropism

Answer 13

• caused by unequal distribution of auxin
• auxin will accumulate on lower surface of the root & stem
• reduces growth on lower surface ; upper surface will grow more, causing the root to grow in the direction of gravity