Download 3 Leaves of Plants

Leaves of Plants
No matter what the size, shape, or texture, leaves have a
very important job for the plant. They make food. Look at the
picture of the maple leaf. The flat part is the blade. Most food
making cells are located here. Throughout the leaf are veins,
which look like tiny ribs. They help support the leaf and contain
xylem and phloem cells like the ones in the root and stem. At the
base of the leaf is the stalk. It is like a larger vein and it connects
the leaf to the stem of the plant.
Materials: leaves from 5 different plants, naturalist’s notebook,
pencil, hand lens
What to do:
and spongy cells absorb water and minerals from the vascular
bundle which contains the xylem and deposit the food they make
in to the phloem cells in the veins.
1. Go to the website
http://nationalzoo.si.edu/Education/ConservationCentral/walk/walk4.html
2. Identify the four trees and draw a sketch of each in your journal.
Make sure to title each sketch and include the scientific name.
3. Label the blade, veins, and stalk and describe their function.
Cells in a Leaf
A leaf has several layers as you can see in the diagram.
The outside layer is the epidermis. It is the skin of the leaf and
helps protect it from wind, rain, and disease. Under the
epidermis are the food making cells. The cells at the top are the
palisade cells. They are long, thin, and tightly packed. Most
photosynthesis occurs here. The cells in the lower part are the
spongy cells. They are odd-shaped and loosely packed. The
veins pass through the spongy, food making cells. The palisade
There are small openings in the epidermis called stomata
(stomata is the plural and stoma is singular). Air goes in and out
of the stomata. If the stomata are blocked, the leaf is unable to
take in carbon dioxide and it will die. Most of the water in the
leaves, about 90% is lost through the stomata. This water loss is
called transpiration and is part of the water cycle. Around each
stoma are two bean-shaped cells. These cells control the size and
opening. They are kind of like balloons. Excess water in the leaf
blows them up and enlarges the opening. When there is little
water in the leaf, they deflate and close the opening.
The pressure that exists inside a cell is called turgor
pressure. As water diffuses into a cell, the pressure on the cell
membrane or cell wall increases, and we say the turgor pressure
also increases. If turgor pressure is maintained, the plant tissue
will remain rigid because it has a cell wall. When the turgor
pressure decreases, the plant wilts.
Materials: plant, naturalist’s notebook, pencil
Name: __________________________ Period: ____ Date: ________
EXIT TICKET – Leaves
What to do:
1. Observe the plant that has just been watered. Gently touch the
leaves and take note of how they feel.
1. Which statement about plant cells is true?
A. They cannot contain both a nucleus and chlorophyll.
2. Draw a sketch of the plant in your journal.
B. They must contain a nucleus, and a cell wall.
3. Wait a week and observe the plant again. Gently touch the leaves
and take note of how they feel.
C. They must contain a cell wall, but can have no nucleus.
4. Draw a sketch of the plant in your journal.
5. Your teacher will water the plant and you will again touch the
leaves and draw a sketch.
Leaves in Autumn
The leaves of most plants are green because they contain the
green pigment chlorophyll. Chlorophyll is also the substance that
takes energy from the sun and converts it to food, or chemical energy
for the plant. Even when light gets to a plant, the plant does not use all
of it. It actually uses only certain colors to make photosynthesis
happen. Plants mostly absorb red and blue wavelengths. When you
see a color, it is actually a color that the object does not absorb. In the
case of green plants, they do not absorb light from the green range, but
instead reflect it. This is why it appears green to our eyes. Plants are
also made of colors other than green.
Watch the demo your teacher will perform. What other colors did you
see on the paper? __________________________________________
D. They have neither a nucleus nor chlorophyll.
2. Which function is shared by roots and stems, but not by leaves?
A. Food production
B. Camouflage
C. Structural support
D. Reproduction
3. What is the name of the small openings in the leaf where water is
lost?
A. Palisade cells
B. Spongy Cells
C. Epidermis
D. Stomata
4. The palisade and spongy cells absorb water and minerals from the
___________________ cells and deposit excess food into the
___________________ cells.
________________________________________________________
All of those colors are in the leaf. In the summer you cannot
see the yellow and orange because they are hidden by the green. When
the weather gets colder the leaves no longer make chlorophyll.
Without the green chlorophyll, the yellow and orange colors are
visible. This is why leaves show more colors in autumn.
5. The process that causes the leaves of the plant to stay full and
plump is called
A. Geotropism
B. Turgor Pressure
C. Phototropism
C. Anisotropic growth