1. Plant Responses and Growth
Life Science
Chapter 5
Section 1

2. Tropisms A plant’s growth response toward or away from a stimlus Touch
Light
Gravity

3. Touch Thigmotropism: Some plants move toward the stimulus
Plants where vines “grab” onto something
Ivy
Morning glories
Green Beans

4. As the light’s position moves, the plant moves toward it.
Phototrophism:
Leave, stems and flowers that move to the light show a positive phototrophism
As the light’s position moves, the plant moves toward it.
Sun Flowers

5. Gavity Gravitrophism:
Plants respond to gravity when the roots grow downward (positive) and the stems grow upward (negative).

6. Plant Hormones
Hormone- a chemical produced by plants that affects how it grows and develops
Controls
Germination
Formation of flowers and stems and leaves
Shedding of leaves
Development of ripening fruit

7. Auxin Important hormone When light hits the stem
Speeds up rate of cell growth
Controls response to light
When light hits the stem
Auxin moves to the shaded area of the stem
Promotes faster growth
Cells on shady side become larger
Stem bends toward light

8. Life Span of Angiosperms
Annuals
Biennials
Plants life cycle that is completed in one year.
Most have herbaceous stems
Most garden plants
Marigolds, tomatoes, cucumbers
Life cycle is completed in two years.
Year one- plant germinates and grow roots, short stems and leaves.
Year two- produce flowers and produce seeds.

9. Life Span of Angiosperms
Perennials
Flowering plants that live for more than two years.
Some have herbaceous stems, most have woody stems
Leaves and stems above the ground die each winter
Examples:
Bristlecone pines
Oak trees
Honeysuckle