Chemical control in plants 9.1

Question 1

What do auxins promote?

Answer 1

-Root growth
-Tropic responses

Question 2

How do auxins cause elongation?

Answer 2

-Active transport of hydrogen ions into cell wall
-Lowers the pH
-This makes the cell wall flexible

Question 3

What do gibberellins stimulate?

Answer 3

-Elongation at cell internodes
-Germination

Question 4

How do gibberellins cause germination?

Answer 4

-Activated embryo secretes gibberellins
-Gibberellins diffuse into aleurone layer
-Aleurone layer produces amylase breaking down starch to glucose

Question 5

What do cytokinins promote?

Answer 5

Cell division in apical meristems

Question 6

What two plant hormones work synergistically?

Answer 6

Auxins and gibberellins

Question 7

What two plant hormones work antagonistically?

Answer 7

Auxins and cytokinins, maintaining apical dominance

Question 8

What is apical dominance?

Answer 8

One lead shoot grows bigger and faster than all the others and growth of lateral buds is inhibited.

Question 9

What is a phytochrome?

Answer 9

A plant pigment that exists as two interconvertible forms

Question 10

What light does Pr absorb?

Answer 10

Red light

Question 11

What light does Pfr absorb?

Answer 11

Far red light

Question 12

In what plants do Pfr stimulate flowering?

Answer 12

Long-day plants

Question 13

What happens to plants grown in the dark?

Answer 13

-All phytochrome is Pr
-They are etiolated

Question 14

What are the features of etiolated plants?

Answer 14

-Tall and thin
-Fragile stems with long internodes
-Little root growth

Question 15

What factor affects time taken for conversion of phytochromes?

Answer 15

Light intensity
High light intensity, conversion takes seconds

Question 16

What is photomorphogenesis?

Answer 16

The process by which the form and development of a plant is controlled by the levels and type of light