1. Plant Hormones and Responses

2. Hormone – chemical that affects the way an organism functions
produced in one part of plant and transported to use in another part
Means “to excite”
Target Cells – the cells that a hormone affects to get a response

3. Parts of the plant most susceptible to hormones
Apical Meristem – part of the plant that is still actively growing (shoot and root)
Lateral Buds – shoots or branches off to the side of the main stem
Fruit – Ripened ovary of an angiosperm

4. Plant Hormones Auxin Cytokinins Gibberellins
Elongates cells for stem growth
Produced by apical meristem
Triggers phototropism
Cytokinins
Promotes cells division and growth
Gibberellins
Causes seed germination (ends dormancy)
Abscisic Acid (Inhibitors)
Prevents water loss by closing stomata
Causes fruit dormancy
Causes leaf fall
Ethylene (Gas)
Causes fruit to ripen
Causes leaves to age

5. Tropism and Nastic Movement
Tropism – growth of a plant or part of a plant in response to a stimulus
Positive – grows towards stimulus
Negative – grows away from stimulus
Nastic Movement – movement of a plant in response to a stimulus

6. Plant Responses Phototropism – plants respond to light grow towards it
Geotropism/Gravitropism – plants respond to gravity and grow against it (roots down, shoots up)
Thigmotropism – plants respond to touch and grow towards those structures in contact
Hydrotropism – plants respond to water and grow towards it

7. What type of tropism is this?

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18. Venus Fly Trap Video
Mimosa Video