Science of Life Explorations
Plannt Anatomy:
Photosynthesis
Plant Anatomy #2
Photosynthesis
What do you know about plants? We’re going to take a closer look at the
anatomy of plants we have in our gardens and fields. ANATOMY is a science of
the structure of an animal or plant or one of its parts.
The plants we have in our neighborhoods generally have three major traits in
common. They have roots, stems and leaves. Let’s talk about the special way
plants make their own food by a process called photosynthesis.
Why do plants have leaves?
What does photosynthesis have to do with me?
Why do plants have leaves? Leaves do the major work of PHOTOSYNTHESIS.
Leaves gather sun energy and CARBON DIOXIDE. They also release water
vapor and OXYGEN. Inside the leaf, plant cells are using carbon dioxide, sun
energy, water and nutrients to create food energy for the plant.
Plant leaves VARY greatly. They all have the purpose of collecting sun energy,
carbon dioxide and water. Look closely and you’ll see that leaves can be
light green, dark green, yellow, thin, thick, fuzzy, smooth, sharp-edged,
smooth-edged, round, pointed, large or small. They can come in groups of one,
two, three, or many more. Some leaves are so different, we call them needles.
This is a great time to take a walk outside and examine the leaves of many
types of plants. You may even have house plants. Don’t forget the leaves of
vegetables and fruits! Compare the leaves below. Do you recognize any of
these plants?
Leaves are famous for one other thing, aren’t they? They fall! Actually,
not all leaves fall, but many do. Most fallen leaves come from plants called
BROADLEAF plants. The National Arbor Society likes to consider trees to
be in two categories: BROADLEAF or CONIFER. Conifers generally have
NEEDLES. Circle the plant above that has needles instead of a ‘broadleaf’.
PHOTOSYNTHESIS is the process plants use to turn sun energy, water,
carbon dioxide and nutrients into food energy!
Plants have specialized cells that contain CHLOROPLASTS.
Below is an illustration of what you would see with a very strong microscope.
A leaf may seem to be pretty thin on some plants but there is a lot of cells
doing specific jobs inside each leaf. Plant leaves are made up of thousands,
maybe millions of cells. Through each leaf run waterways called VEINS.
Leaves also have tiny openings that take in carbon dioxide and release oxygen
found in the air around us. Because this is so important, we’ll discuss it again
later, too.
Here is one plant cell !
Along with many other
parts, the important
chloroplasts are found here.
The leaf is just
one of the three
important parts of
a plant
Here is a cross section
of a plant leaf with
many cells. See the
leaf vein?
leaf,
stem
don’t forget
the roots!
“Reproduced by permission of Morton Publishing from
Van De Graaff and Crawley, A Photographic Atlas for
the Biology Laboratory, 5th Edition. © 2005”
We can see the leaves, stems and roots of a plant, but this illustration shows us
what a plant cell and leaf look like under extreme magnification. Do you see
the many cells that make up a leaf? The leaf vein carries water and nutrients
and food energy to the stem. It is part of the circulatory system that runs
through the stems and leaves of plants called VASCULAR BUNDLES.
What does photosynthesis have to do with you? Photosynthesis is the process
in which plants make their own food energy. Plants take in nutrients and water
through their roots, and take in carbon dioxide through their leaves. Using the
sun’s energy, cells in their leaves create food energy. Leaves release oxygen
into the air. This is good for us. Animals and people take oxygen out of the air
and release carbon dioxide. That is a pretty good system, isn’t it? Next to the
plant, draw yourself. Show the exchange of oxygen and carbon dioxide that you
create.
sun energy
carbon dioxide
oxygen
water and nutrients
If you remember our lesson about the food chain, you’ll remember that people
and animals can’t make their own food energy, but must be CONSUMERS of
energy. Most of our food energy comes from plants directly or indirectly.
Let’s review plant anatomy.
Plants are unique because they have the ability to make their own food energy!
Most plants have roots, stems and leaves. These plant parts do the same types
of work, but they may vary quite a lot.
Plant leaves can be many shapes, sizes and thicknesses. When people talk about
shrubs and trees, they may separate them into groups called broadleaf plants
and conifer plants. Conifers usually have needles. Needles are special leaves
that usually stay on the plant all year long. Because of this, many people call
them evergreens.
The special way plants create energy is called photosynthesis. That process
is also good for us. Plants take in carbon dioxide and release oxygen. People
and animals take in oxygen and release carbon dioxide. Without plants, our air
would not be healthy to breathe!
Vocabulary
anatomy - the science that deals with the structure of an animal or plant or one
of its parts
angiosperm - the scientific name for plants that produce flowers as part of
their life cycle
annual - plants that survive one growing season in a particular area
broadleaf - the term for plants that have broad leaves rather than needles
cambium- a layer of cells under bark and phloem; new cells are formed along
this layer which cause the plant to grow larger each year
carbon dioxide - a gas in our atmosphere that plants use to make their own food
energy; animals exhale carbon dioxide into the air
chloroplasts - an important part of plant cells that enables plants to create
food energy for themselves in the process of photosynthesis
circumference - the measurement of something all the way around it
conifer - a term for plants that produce narrow needle-like leaves rather than
broad leaves
consumers - animals or people that acquire (eat, buy, take) products created by
others
cotyledon - the first and very important leaf or leaves of flowering plants
crown - a tree crown is all the branches and leaves of the tree; a plant crown
is the base of the plant at ground level, above the roots and the source of new
leaf growth
deciduous - the term for woody plants that drop their leaves before winter
dicot - the term for a flowering plant which produces two leaves on its shoot
and will develop branches and leaves when mature
dormant - for plants, this means active growth stops due to a change in season
essential -something that is very important and needed
estimate - a good guess or calculation of something based on the information
you can gather about it
evapo-transpiration - the way that plants release water back into the soil
through their leaves; it is a form of evaporation when water changes into a
vapor
evergreen -the general term used for plants that don’t lose their leaves; most
are conifers, but not all
gymnosperm - the scientific name of plants that don’t produce flowers but
create seed-bearing cones instead
herbaceous - plants that do not produce a woody covering to their stems and
generally die back in the winter
monocot - plants that send up one shoot and one new leaf only, and will mature
to have only one stem
needles - the name for the narrow ‘needle-like’ leaves of conifers
oxygen - the gas found in our atmosphere that animals must inhale to to nourish
their cells and stay alive; plants release oxygen
perennial - plants that complete a life cycle in one season and resume growth
again for more than one year
phloem - phloem is the part of plants that transports food energy from leaves
down to the roots.
photosynthesis - the way plants create their own food energy
protista - the scientific kingdom that includes fungi, molds, algae and other
organisms
shrub - similar to a tree but usually has more than one woody stem
stem - the stalk or trunk of a plant; there can be one or many stems on a plant
trait - a quality of or a feature of something that stays constant
trunk - the woody stem of some plants, especially shrubs and trees
turf - grass that is grown and maintained to be a lawn or outdoor use area
unique - one of a kind; not like others
vary - to show variety or differences
vascular bundles - plant tissue that acts as waterways to move food energy,
nutrients and water throughout the plant
veins - tube-like structures which allow water and sugars to travel through
plants or in the case of animals, blood to the heart
woody - a plant that has bark over its stem rather than soft green tissue
xylem - xylem is the part of a plant that transports water and nutrients up to
leaves
Pg 1 This is a great time to explore the outdoors and collect leaves. Another option
is to have students design a leaf of their own and describe the plant it came from.
Remind students that leaves tend to be symmetrical.
Pg 2 Plant cells contain some of the same types of functioning parts as other cells, such
as cell walls, a nucleus and mitochondrion. All plant cells are similar, but as in any type of
living organism make up different parts of the plant depending where they are located.
Plant cells contain the important chloroplasts used for photosynthesis. In the leaf crosssection, students will see that many cells make up even the smallest areas. Some cells
are joined to create the leaf veins. Have students examine the leaf veins on different
plants. Are they always raised, or noticeable? Do they tend to be lighter or darker than
the rest of the leaf? Are they larger or smaller near the stem?
PG 3 To reinforce the idea of photosynthesis, this page shows the plant’s cycle of
carbon dioxide in and oxygen out. Have students draw themselves, plus some arrows
and the words CARBON DIOXIDE and OXYGEN to illustrate how humans interact with the
atmosphere. Is it the same as plants or opposite. Can opposite be a good thing? Why
should we protect the atmosphere from pollutants? Can having more or less plants help?