Plant Growth

Question 1

What are auxins

Answer 1

Plant hormones stimulate growth

Question 2

How do auxin affect the plant growth

Answer 2

1)IAA is made in the shoot tip and diffuse back towards the zone of elongation

2)they bind to specific receptor sites on the cell surface membrane —> activates the hydrogen pump and hydrogen ion goes into the cell wall spaces

3)this changes the hydrogen ion concentration providing the optimum pH of around 5 for enzyme to break bond of neighbouring cellulose microfibrils

4) this allows the microfibrils to slide past each other making the walls very plastic and flexible

5) the cells then absorb the water by osmosis and the cell elongates and expands

6)when the cell matures, the IAA is destroyed by enzyme the pH of the cell walls rises the enzyme are inhibited and the bond form between cellulose microfibrils

7) the cell stop expanding since the wall become rigid again

Question 3

Affect of light on the distribution of auxin

Answer 3

1) light Causes the auxins to move laterally across the shoot producing a greater concentration on the unlit side

2)shoot tip acts as photoreceptors

3)more of the hormones diffuse down to the region of cell elongation on the darker side —> more cell elongation on the darker side —> more growth

4) so the shoot bend towards the light

5) once the shoot is growing directly towards the light, there is no longer a brighter side or darker side

6)the auxins again becomes evenly distributed and growth towards the light

Question 4

GIBBERELLINS

Answer 4

1)seed absorb water and swells - embryo activated

2)embryo secretes giverellins diffuse to aleurone layer

3)gibberellins stimulate aleurone layer to produce amylase that diffuse into endosperm and break down food stores to provide embryo with material for respiration and growth

4)enzyme produced in response to gibberellin digest the endosperm. Product released from endosperm are used by embryo to make new cells and germinate

Question 5

What is synergy

Answer 5

The growth regulators or hormones interact and work together for greater response

Question 6

What is antagonism

Answer 6

The growth regulator or hormones have opposite effect

Question 7

What is Pr

Answer 7

Stable form and absorb red light
Active and absorb red light

Question 8

What Pfr

Answer 8

Active and absorb far red light