Download Notes 8-5

Exploring Life Science
Chapter 8
Plants
Chapter 8 – Plants
Engage:
What do plants respond to?
Objectives:
1. Identify 3 stimuli that produce plants responses.
2. Describe how plants respond to seasonal changes.
3. State how long different angiosperms live.
8-5 Plants Responses and Growth
A. Tropisms – Plant growth response toward or away
from stimulus.
1. Touch  Thigmotropism – Thigmo = “Touch”
 Bladderworts
 Vines- grow around what they touch.
2. Light –
 Stimulus
TROPISM
response
Positive tropism - growth toward stimulus.
Negative tropism - growth away from stimulus.
Response
Stimulus
Phototropism =
light
plant grows toward
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Exploring Life Science
Chapter 8
Plants
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Exploring Life Science
Chapter 8
Plants
3. Gravity
 Gravitropism
 Roots – Positive
 Stems – Negative
4. Hormones & Tropisms
 Hormones – chemical that affects how the
plant grows and develops.
 Auxin – hormone that speeds up the rate at
which a plant’s cells grow.
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Exploring Life Science
Chapter 8
Plants
B. Seasonal Changes
1. Photoperiodism – a plant’s response to
seasonal changes in length of night and day.
 Short-day plants – flower when nights are
longer.
 Long-day plants – flower when nights are
shorter.
 Critical night length – is the number of
hours of darkness – ex. 11 hours
 Day-neutral plants – flowering cycle is not
sensitive to periods of light and dark.
2. Dormancy- period when an organisms growth or
activity stop.
 Causes – lack of liquid water
 Fall colors – plant stops producing
chlorophyll other pigments become visible.
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Exploring Life Science
Chapter 8
Plants
C. Life Spans of Angiosperms
1. Annuals, Biennials, and Perennials
 Annuals -- plants that complete
their life cycle within one growing
season.
Annus = year
(Ex: Marigolds, petunias, garden
flowers, wheat, rye & tobacco plants).
 Biennials -- plants that complete
their life cycle in two years.
Bi = two
Sprout & grow roots, stems & leaves
1st year roots survive winter.
2nd year flowers & seeds.
(Ex: Sugar beets, carrots, celery and
foxgloves).
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Exploring Life Science
Chapter 8
Plants
 Perennials -- plants that live many
years.
Per = through
Through many years.
Herbaceous = garden peonies
Woody = pine trees, rhododendron
bushes, lilacs.
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