Download Section 23.2 Summary – pages 612

1. What are the main parts of this tree?
2. What is the function of each part?
REVIEW
How do plants obtain energy?
In the food chain, they are the producer….
PLANT STRUCTURE AND FUNCTION
Roots:
Anchors the plant
Collects water and
nutrients for plant
LEAVES
Cannot carry out photo.
Stem:
Above ground
Transports nutrients
If green, can
photosynthesize
STEM
Leaves: Major Photosynthesis
Transpiration
ROOTS
Remember Capillary
Action and Adhesion
ROOTS
Roots can be short or long
Rhizome
Roots can be thick and
Most
massive
roots or
grow in the soil,
thin and thread-like. some do not….
TYPES OF ROOTS
1.
TAPROOTS: like carrots and beets
single thick structures with
smaller branching roots
accumulate and store food
TYPES OF ROOTS
2.
Fibrous Roots: have many small branching
roots from a central point
example: grass
TYPES OF ROOTS
3.
PROP ROOTS: originate above ground to
help support the plant
example: corn
Plant Hormones
• Plants, like animals, have hormones that regulate
growth, help them respond to the environment, and
send chemical messengers.
• A hormone is a chemical that is
produced in one part of an
organism and transported to
another part, where it causes a
physiological change.
• The plant’s hormones are
produced in the ROOTS.
STEMS
Stems transport water, dissolved minerals, and
sugar to and from roots and leaves.
1.
Herbaceous Stems
Fleshy, green stems,
Can also carry out photosynthesis.
2.
Woody stems
Grow year after year
Have cork tissue for protection
A tree trunk is one example of a woody stem.
Woody stems are composed primarily of dead xylem cells.
Annual growth rings
• These annual growth
rings can be used to
estimate the age of
the plant.
Cork
Phloem
Vascular
cambium
Xylem
Besides age, the thickness of a tree can show
how much water was available at the time.
A thin tree ring indicates a year of drought.
LEAVES
• The primary function of the leaves is photosynthesis.
• Sunlight passes through the transparent cuticle into
the photosynthetic tissues just beneath the leaf
surface.
Cuticle
Upper epidermis
Palisade Layer
(where most chloroplasts are found)
LEAVES
Size, Shape, and type of
leaves vary enormously.
Opposite Arrangement
LEAVES
• Gases can also move in and out of a leaf through the
stomata, which are located in the upper and/or lower
epidermis.
Stomata
LEAVES
• Guard cells are tiny cells that surround and
control the size of a stoma.
• The loss of water through the stomata is called
transpiration.
LEAVES
Stoma
Transpiration
Water
• When water enters
the guard cells, the
pressure causes
them to bow out,
opening the stoma.
Guard
cell
LEAVES
Transpiration
• As water leaves the
guard cells, the
pressure is released
and the cells come
together, closing the
stoma.
Water
LEAVES
One way to distinguish among different groups of plants
is to examine the pattern of veins in their leaves.
PARALLEL VEINS
NET-LIKE VEINS
(Monocot)
(Dicot)
PLANT RESPONSES
• Although a plant lacks a nervous system and
usually cannot make quick responses to
stimuli, it does have mechanisms that enable it
to respond to its environment.
• Plants can respond to:
Gravity
Light
Temperature
PLANT RESPONSES
• Tropism is a plant’s response to an external
stimulus.
• The tropism is called positive if the plant grows
toward the stimulus.
• The tropism is called negative if the plant
grows away from the stimulus.
WE WILL LOOK AT THREE TYPES OF
TROPISM
TROPISM
The growth of a plant toward light is called phototropism.
• As these cells
lengthen, the stem
bends toward the light.
TROPISM
Gravitropism is plant growth in response to gravity.
Stems usually exhibit a negative gravitropism.
Roots that grow down into the soil are able to anchor the
plant and can take in water and dissolved minerals.
How do growing seeds exhibit both phototropism and gravitropism?
TROPISM
Some plants exhibit another tropism called
thigmotropism, which is a growth response to touch.
• Because tropisms involve growth, they are not reversible.
• The position of a stem that has grown several inches in a
particular direction cannot be changed.
Ivy is a good example of a plant that exhibits all three types of tropism.
PLANT RESPONSES
• A responsive movement of a plant that is not
dependent on the direction of the stimulus is
called a nastic movement.
• An example of a nastic response is the sudden
closing of the hinged leaf of a Venus’s-flytrap.
• Naustic movements do not involve growth.
• The relative lengths of daylight and darkness each day
have a significant effect on the rate of growth and the
timing of flower production in many species of
flowering plants.
• The response of flowering plants to daily daylightdarkness conditions is called photoperiodism.
Question 1
Most plants produce their own food in the form of
_______.
A. cellulose
B. proteins
C. glucose
D. chlorophyll
The answer is C.
Question 2
Which of the following is NOT a function of most
plant roots?
A. absorbing water and nutrients
B. conducting photosynthesis
C. store starch
D. anchoring the plant
The answer is B.
Question 3
Most roots that humans eat are _____ roots.
A. taproots
B. fibrous roots
C. prop roots
D. aerial roots
The answer is A, taproots.
Question 4
If a plant becomes too dry, are the stomata in
the leaves more likely to be open or closed?
Answer
The stomata are more likely to be closed to
prevent any more water loss from the plant.
Question 5
What is the main difference between tropisms and
nastic responses?
Answer
The main difference between the two is that
tropisms are not reversible and nastic responses
are reversible. Also, nastic responses do not
depend on the direction of the stimulus, tropisms
do.
Question 6
As you walk through a room, you notice that a
plant sitting on a table 2 m from a window is
leaning toward the window. What type of
response is the plant exhibiting?
Answer
phototropism.
Question 7
Name the two stages of a plant’s life cycle, and
describe which each entails.
Answer
Gametophyte: Haploid stage
Sporophyte: Diploid stage