Plant Control and Hormones

1
Plant Control and Hormones

• Plants do not behave as animals do, but have
  control systems instead.

2
Phototropism

• Phototropism is the movement of plants towards
  light.

3
Gravitropism

• Roots move down and shoots grow up in the dark in
  response to gravity.

4
These plants were situated in various positions,
but the shoots continued to move against gravity.
5
Thigmotropism

• Thigmotropism is a plants response to touch This
  plant responds to a stationary object by wrapping
  its stem around it to anchor itself

6
This plant responds to touch by wilting. What
advantage may this be to the plant?
7
Photoperiodism - Some plants respond to the
amount of daylight Poinsettia turn red and
flower in response to shorter days
8
Some plants flower in response to longer days
such as the spinach plant
9
There are 5 main hormones in plants that cause
them to react to stimuli

• Auxins
• Gibberellins
• Ethylene
• Cytokinins
• Abscisic acid

10
Auxins

• Responsible for all tropisms such as
  phototropism and gravitropism also for stem
  elongation and root initiation

11
Gibberellins

• Responsible for stem elongation and for seed
  germination
• Dwarf plants have very little gibberellins
• Jacks bean stalk had a lot!

12
Ethylene

• Ethylene causes fruit to ripen.
• If you put ripe fruit in a bag with unripe fruit,
  your unripe fruit will ripen more quickly. This
  is because ethylene is a gas. Hence the saying
  One bad apple spoils the whole barrel

13
Cytokinins

• Responsible for cell division in plants

14
Abscisic Acid

• Important for seed and bud dormancy.