Plant Responses and Growth Life Science Chapter 5 Section 1

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

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

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

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

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

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

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.

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