KEY CONCEPT
Plants are adapted to
living on land.
Sunshine State
STANDARDS
SC.F.1.3.1: The student
understands that living
things are composed
of major systems
that function in
reproduction, growth,
maintenance, and
regulation.
SC.F.1.3.5: The student
explains how the life
functions of organisms
are related to what
occurs within the cell.
BEFORE, you learned
NOW, you will learn
• All organisms have certain
basic needs and characteristics
• The bodies of multicellular
organisms are organized
• Plants are producers
• About plant diversity
• About common characteristics
of plants
• How the bodies of plants
are organized
EXPLORE Leaf Characteristics
What is a leaf?
PROCEDURE
1
VOCABULARY
vascular system p. 377
transpiration p. 378
Examine the leaf your teacher gives you
carefully. Try to notice as many details as
you can.
MATERIALS
• assorted leaves
• hand lens
2 Make a drawing of both sides of your leaf in your notebook.
Label as many parts as you can and write down your ideas
describing each part’s function.
3 Compare your diagram and notes with
those of your classmates.
WHAT DO YOU THINK?
• What characteristics did most or
all of your leaves have?
• How would you describe your leaf
to someone who could not see it?
Plants are a diverse group of organisms.
MIND MAP
Make a mind map for
the first main idea:
Plants are a diverse
group of organisms.
Plants are nearly everywhere. Walk through a forest, and you’re surrounded by trees, ferns, and moss. Drive along a country road, and
you pass fields planted with crops like cotton or wheat. Even a busy
city has tree-lined sidewalks, grass-covered lawns, and weeds growing
in vacant lots or poking through cracks in the pavement.
Earth is home to an amazing variety of plant life. Plants come in
all shapes and sizes, from tiny flowers no bigger than the head of a pin
to giant trees taller than a 12-story building. Plants are found in all
types of environments, from the icy Arctic to the steamy tropics.
Chapter 11: Plants 375
Diversity of Plants
Plant species live in a variety of environments and have a wide range of features.
Orchids
Horsetails
Bristlecone Pine
Seed pods of the vanilla
orchid are used to flavor food.
Horsetails have a distinctive
shape and texture.
Bristlecone pines are some of
the oldest trees on Earth.
Plants share certain characteristics.
Scientists estimate that at least 260,000 different species of plants live
on Earth today. The photographs on this page show three examples of
plants that are very different from one another.
re
reminder
The word species comes
from a root word meaning
“kind” or “type.”
In science, species is a
classification for a group of
organisms that are so
similar that members of the
group can breed and
produce offspring that can
also reproduce.
Orchids are flowering plants that mostly grow in tropical rain
forests. To get the sunlight they need, many orchids grow not in the
soil but on the trunks of trees. Horsetails are plants that produce tiny
grains of a very hard substance called silica. Sometimes called scouring rushes, these plants were once used to scrub clean, or scour, dishes
and pots. Bristlecone pine trees live on high mountain slopes in North
America, where there is little soil and often high winds. These trees
grow very slowly and can live for several thousand years.
You can see from these three examples that plant species show
great diversity. Despite how different an orchid is from a horsetail and
a bristlecone pine, all three plants share certain characteristics. These
are the characteristics that define a plant as a plant:
•
•
•
•
Plants are multicellular organisms.
A plant cell has a nucleus and is surrounded by a cell wall.
Plants are producers. They capture energy from the Sun.
Plant life cycles are divided into two stages, or generations.
Check Your Reading
376 Unit 3: Diversity of Living Things
What characteristics are shared by all plants?
Plant parts have special functions.
You could say that a plant lives in two worlds. The roots anchor a
plant in the ground. Aboveground, reaching toward the Sun, are stems
and leaves. Together, stems and leaves make up a shoot system. These
two systems work together to get a plant what it needs to survive.
A plant’s root system can be as extensive as the stems and leaves
that you see aboveground. Roots absorb water and nutrients from the
soil. These materials are transported to the leaves through the stems.
The leaves use the materials, along with carbon dioxide from the air,
to make sugars and carbohydrates. The stems then deliver these
energy-rich compounds back to the rest of the plant.
C
heck Your Reading
reminder
Plants, like animals, have
several levels of organization. The root system and
shoot system are organ
systems.
What are two plant systems, and what are their functions?
Transporting Water and Other Materials
Stems serve as the pathway for transporting water, nutrients, and
energy-rich compounds from one part of a plant to another. In
most plants, the materials move through a vascular system
(VAS-kyuh-lur) that is made up of long, tubelike cells. These
tissues are bundled together and run from the roots to the leaves.
A vascular bundle from the stem of a buttercup plant is shown.
phloem
Transport is carried out by two types of tissue. Xylem (ZY-luhm)
is a tissue that carries water and dissolved nutrients up from the roots.
Phloem (FLOH-em) is a tissue that transports energy-rich materials
down from the leaves. Xylem cells and phloem cells are long and hollow,
like pipes. The xylem cells are a little larger than the phloem cells. Both
tissues include long fibers that help support the plant body, as well as
cells that can store extra carbohydrates for energy.
xylem
This vascular bundle has
been magnified 113 .
Vascular System
The vascular system transports
materials throughout a plant’s body.
leaves
stems
Sugar is produced in the
leaves and transported
downward to other parts
of the plant.
roots
Water and nutrients
enter through the roots and
are transported upward to
the rest of the plant.
Chapter 11: Plants 377
Making Sugars
Plants produce sugars through the process of photosynthesis.
Photosynthesis is a series of chemical reactions that capture light
energy from the Sun and convert it into chemical energy stored in
sugar molecules. The starting materials needed are carbon dioxide,
water, and light. The end products are sugars and oxygen. The chemical reactions for photosynthesis can be summarized like this:
carbon dioxide water sunlight → sugars oxygen
Photosynthesis takes place in chloroplasts, structures that contain
chlorophyll. Chlorophyll absorbs the sunlight that the chloroplasts need
to produce the reaction. Most chloroplasts in a plant are located in leaf
cells. As you can see from the illustration on page 379, the structure of
the leaf is specialized for capturing light energy and producing sugar.
Check Your Reading
FLORIDA
Content Review
reminder
Remember what you
learned about the importance of photosynthesis in
cell functions in Chapter 6.
Open Stomata
214 Closed Stomata
What is photosynthesis, and why is it important?
The upper surface of the leaf, which is turned toward the Sun, has
layers of cells filled with chloroplasts. Vascular tissue located toward
the center of the leaf brings in water and nutrients and carries away
sugars and other carbohydrates. Tiny openings at the bottom of the
leaf, called stomata (STOH-muh-tuh), lead to a network of tiny spaces
where gases are stored. The carbon dioxide gas needed for photosynthesis comes in through the stomata, and oxygen gas moves out. This
process is called gas exchange.
Controlling Gas Exchange and Water Loss
For photosynthesis to occur, a plant must maintain the balance of
carbon dioxide and water in its body. Carbon dioxide gas from the air
surrounding a plant enters through the stomata in its leaves. Open
stomata allow carbon dioxide and oxygen to move into and out of the
leaf. These openings also allow water to evaporate. The movement of
water vapor out of a plant and into the air is called transpiration
(TRAN-spuh-RAY-shuhn). Both sunlight and wind cause water in
leaves to evaporate and transpire.
For photosynthesis to occur, a plant needs to have enough carbon
dioxide come in without too much water evaporating and moving
out. Plants have different ways of maintaining this balance. The surfaces of leaves and stems are covered by a waxy protective layer, called
a cuticle. The cuticle keeps water from evaporating. Also, when the air
is dry, the stomata can close. This can help to prevent water loss.
Check Your Reading
378 Unit 3: Diversity of Living Things
What are two ways plants have to keep from losing too
much water?
Inside a Leaf
The leaf is an organ that produces sugars.
It is made up of different types of cells
and tissues.
Cells at the surface produce
a waxy cuticle that keeps
the leaf from losing water.
Most chloroplasts are
located in cells of the
upper layer of the leaf.
Xylem transports water and
nutrients up from the roots.
Carbon dioxide, oxygen,
and water vapor move
into and out of the leaf
through stomata.
Phloem transports energy-rich
compounds made in the leaf
down to other parts of the plant.
How is the top of a leaf different from the bottom of a leaf?
Chapter 11: Plants 379
stem
spines
The stomata are an adaptation that allows a
plant to adjust to daily changes in its environment.
Plants can respond to hot, dry weather by keeping
their stomata closed. Stomata can be open during
the night, when evaporation is less likely to occur.
Most plants have stomata.
Some species of plants have special adaptations
for survival in a particular environment. For example, a cactus plant has adaptations that allow it to
survive in a desert. The spines of a cactus are actually modified leaves. A plant with regular leaves
would lose too much water through transpiration.
In cacti, most photosynthesis occurs in the thick
fleshy stem, where the cactus also stores water and
carbon dioxide gas.
APPLY Plant stems branch
as they grow. Do cactus
plants have branches?
Plants grow throughout their lifetimes.
Plants grow as long as they live. This is true for plants that live for
only one season, such as sunflowers, and for plants that can live for
many years, such as trees. Plants grow bigger when cells at the tips of
their roots and stems divide and multiply more rapidly than other
plant cells do. A plant’s roots and stems can grow longer and thicker
and can branch, or divide. However, only stems grow leaves. Leaves
grow from buds produced by growth tissue in a plant’s stems. The bud
of an oak tree is shown on page 381.
Plant stems are structures with more than one function. You have
read that a plant’s stem includes its vascular system, which allows the
plant to transport materials between its leaves and roots. Long stiff
fibers in the tissues of the vascular system provide support and give
the plant shape. Plant stems can also store the sugars produced by
photosynthesis. Many plants, including broccoli, celery, and carrots,
convert sugars into starch and then store this energy-rich material in
their stems or roots.
Check Your Reading
RESOURCE CENTER
CLASSZONE.COM
Learn more about plant
systems.
What are three functions of plant stems?
Plants with Soft Stems
The soft stems and leaves of many wildflowers, garden flowers, and
vegetables die when the environment they live in becomes too cold or
too dry. This type of plant survives by using the carbohydrates stored
in its roots. Then, when the environment provides it with enough
warmth, water, and sunlight, the plant will grow new, soft, green stems
and leaves.
380 Unit 3: Diversity of Living Things
Plant Growth
Plants, such as these oak trees, grow most when there is enough warmth,
water, and sunlight.
Oak Bud
The tips of the shoots produce buds, which become
new leaves and stems.
Plants with Woody Stems
Some plants, such as trees and shrubs, have tough, thick stems that do
not die each year. These stems keep growing longer and thicker. As the
stems grow, they develop a type of tough xylem tissue that is not found
in soft stems. This tough xylem tissue is called wood. The growing tissues in woody stems are located near the outer surface of the stem, right
under the bark. This means that, for a tree like one of the oaks in the
photograph above, the center of the trunk is the oldest part of the plant.
KEY CONCEPTS
CRITICAL THINKING
1. What characteristics do all
plants have in common?
4. Summarize Describe how the
structure of a leaf allows a
plant to control the materials
involved in photosynthesis.
2. How does the structure of a
leaf relate to its function?
3. What tissues move materials
throughout a plant?
CHALLENGE
6. Evaluate Scientists who study
the natural world say that
there is unity in diversity. How
does this idea apply to plants?
5. Analyze Do you think the
stems of soft-stemmed plants
have chloroplasts? How about
woody-stemmed plants?
Explain your reasoning. Hint:
Think about the color of each.
Chapter 11: Plants 381