1. Plant Responses and Adaptations
Slide # 16
Plant
Responses
and
Adaptations

2. Hormone Action on Plants
Hormone-producing
cells
Target
Movement
of hormone
Plant cells can produce hormones which are chemical messengers that travel throughout the plant causing other cells called target cells to respond.
In plants, hormones control:
Plant growth & development
Plant responses to environment
Cells in one blooming flower signals other blooms to open using hormones.

3. Plant cells will send signals to one another to tell them:
When to drop their leaves.
When to start new growth.
When to cause fruit to ripen.
When to cause flowers to bloom.
When to cause seeds to sprout.
Leaf Drop
Tree Budding
Fruit
Ripening
Cactus
Blooming
Sprouting
Corn Seeds

4. There are 5 major classes of hormones
Gibberellins
Cytokinins
Oligosaccharins
Abscisic Acid (ABA)
Ethylene

5. Gibberellins Are produced in the apical meristem.
They promote stem growth.
Gibberellins also increase the starch uptake of the embryo, stimulating the development of vascular tissue.

6. Cytokinins Cytokinins promote cell division and cell differentiation.
They also delay the aging of fruit and leaves.

7. Oligosaccharins
Stimulate plants to produce antibiotics in response to attack by fungi or bacteria.

8. Abscisic Acid (ABA)
Is a growth inhibitor and is mainly manufactured in mature leaves.
ABA inhibits the growth of
germinating seeds
Growth of buds
Plant stems
and blocks the uptake of CO2 by controlling leaf stomata

9. Ethylene causes Fruit to Ripen
Fruit tissues release a small amount of ethylene
Causes fruits to ripen.
As fruit become ripe, they produce more and more ethylene, accelerating the ripening process.
Ethylene released by apples and tomatoes causes fruit to age quickly.

10. Adaptations: Plant Tropisms
1. Tropism: the way a plant grows in response to stimuli in the environment.
Phototropism: growth response to light
-Plants bend towards light
b. Geotrophism: growth response to gravity
-plant roots grow down with gravity, shoots (stems) grow up against gravity and out of the soil.
c. Thigmotropism: growth response to touch
-vines grow up around trees, Venus flytrap closes when leaves are touched

11. Geotropism Thigmotrophism Geotropism Phototropism
What type of tropism is shown in these pictures?
Geotropism
Phototropism
Thigmotrophism
Geotropism
Phototropism