1. Plant Responses and Hormones
Plants respond to internal and external stimuli which cause them to change their growth and development.

2. Plant Hormones
A group of chemicals called hormones can control plants growth and development.
Plant hormones are chemical substances that control patterns of development as well as plant responses to the environment
Most hormones promote growth.

3. Auxins Auxins stimulate cell elongation
Responsible for plant responses to external stimuli (tropisms)

4. Cytokinins
Cytokinins stimulate cell division and cause dormant seeds to grow.

5. Gibberellins Responsible for stem elongation and seed germination
Gibberellins cause dramatic increases in size of the plant, especially stems and fruit.
Dwarf plants have very little gibberellins

6. Which Banana Ripens Faster?
Bananas in a bunch, single banana, or it makes no difference?
Class tally:
Answer:
Single
Bunch
No difference
IIIIIIIIIIIIIIIIIIIIIII
IIIIII
IIII
Bananas in a bunch ripen fastest!

7. Ethylene Ethylene stimulates fruits to ripen.
It is a gas - “One bad apple spoils the bunch”

8. Tropisms
Plants grow, reproduce, and shift the position of their roots, stems, and leaves in response to environmental conditions such as light, gravity, and touch.
The responses of plants to external stimuli are called tropisms.

9. Phototropism
Plants grow toward the light

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

11. Photoperiodism
Some plants respond to the amount of daylight available to them
Example 1: Poinsettia turn red and flower in response to shorter days
Example 2: Some plants flower in response to longer days such as the spinach plant