Co-Ordination in Plants

Question 1

Observe and interpret seedlings grown in uniform light

Answer 1

Grows slower, stronger and greener

Question 2

Observe and interpret seedlings grown in one-sided light

Answer 2

plant will bend and grow towards the light
Positive phototropism

Question 3

Observe and interpret seedlings grown in no light

Answer 3

stems will be longer, thinner, weaker, grow faster have longer internodes

Question 4

Define plant growth substances

Answer 4

Chemicals that affects the activities of particular cells and organs

Question 5

Define gravitropism

Answer 5

A response in which parts of a plant grows toward or away from gravity

Question 6

Define phototropism

Answer 6

A response in which parts of a plant towards or away from the direction from which light is coming

Question 7

Advantages of gravitropism

Answer 7

Roots grow downward in soil to reach water and minerals
Roots are anchored and stable in the soil
Seeds grow in the soil

Question 8

Advantages of phototropism

Answer 8

Stems grow towards light- larger surface area
Maximum light absorption
Photosynthesis
Flowers exposed for pollination

Question 9

Describe the effects of synthetic plant growth substances used as weedkillers

Answer 9

Contain synthetic plant hormones such as auxin.
It is sprayed onto the leaves of plants in high concentrations.
Translocate into the phloem up and down the plant.
Moves by diffusion through cell membrane
Plant leaves and stems are stimulated to grow rapidly and die (only dicots)

Question 10

What role does auxin play in phototropism?

Answer 10

Auxin produces at the tip of the stem, diffuses, and accumulates on the shaded side.
Differential growth: shaded side grows faster and the lighted side grows normally

Stem bends in the direction of light source.

Question 11

What role does auxin play in gravitropism

Answer 11

Auxin produces at the tip of the root, diffuses, and accumulates on the under side.
Differential growth: lower side grows slower and upper side grows normally

Bending of root in the direction of gravity.