Observing Root and Stem structures
The first structures to appear on a germinating seed are the roots. The initial root to grow from a
seed is the primary root, which is followed by secondary roots that branch out from the primary root.
In a taproot system, the primary root grows longer and thicker than the secondary roots. In a fibrous
root system, the secondary roots continue to grow, and eventually all the roots are of equal or nearly
equal size.
Roots anchor the plant in place, absorb water containing dissolved minerals from the
environment, and act as storage areas for excess food.
Plant structures that grow between the roots and leaves are called stems. Although stems
usually grow above the ground in vertical positions, they can also grow under the ground in
horizontal positions. Stems conduct water and dissolved minerals from the roots to the leaves, and
food from the leaves to the rest of the plant. Stems may also function as food storage areas,
supporting structures, and places for the growth of new plants.
In this investigation, you will examine the structures of roots and stems. You will also
observe the structural differences between some monocot and dicot roots and stems.
Procedure:
1. Examine the radish seedling. Note the basic structures
of the seedling: leaves, stem, and roots. Draw what you
see in the box and label these parts.
2. Examine the two halves of the carrot. Each half is a longitudinal section. Notice the inner
section, called a stele that contains the xylem and the phloem. Surrounding the stele is the foodstoring cortex. In the labeled box, sketch a longitudinal section of the carrot. Label the stele and the
cortex.
2. Get a cross section of the carrot. Cover the cross section completely with methylene blue
stain. Allow the stain to set for 1 minute. After 1 minute, slowly pour alcohol over the cross
section until no more stain washes away.
3. Observe the cross section of the carrot under a dissecting microscope. In the labeled box,
sketch the cross section of the carrot. Label the stele and cortex.
Longitudinal section of carrot
Cross section of carrot
4. There are many different kinds of angiosperms in the world. Scientists divide all angiosperms
into two major categories: Monocots and Dicots. These two classes separate angiosperms by their
major characteristics. Fill out the following table about the differences between monocots and
dicots. Use page 570 in the dragonfly book to help.
Monocots
Dicots
Seeds
Leaves
Flowers
Stems
Roots
5. Look at the grouping of plants in the tray. Identify each plant as either a monocot or a dicot
based on its characteristics:
a. Monocots:
a. Dicots:
6. As you determined in the table listed above, monocots and dicots differ in the organization of
their roots and stems. Observe the photograph of a sunflower and corn root cross section.
What are some observations about how their xylem and phloem are organized? Also, circle
whether they are monocots or dicots.
a. Corn root(monocot or dicot?):
b. Sunflower root (monocot or dicot?):
7. Observe the photograph of a sunflower and corn stem cross section. What are some
observations about how their xylem and phloem are organized?
a. Corn stem:
b. Sunflower stem
c. The diagram (10.2) on page 296 is a cross section of a sunflower stem drawing. Draw it in the
box above, and label the vascular bundles, epidermis, cortex, and pith.
8. Get a copy of the numbered diagrams of roots and stems. For each diagram, list whether it is
a monocot or a dicot.
a. Diagram 1:
b. Diagram 2:
c. Diagram 3:
d. Diagram 4:
e. Diagram 5:
9. Plants often modify their parts to suit their needs. These four modifications offer different
advantages for the plant. For each modification, list the function / advantage it gives the
plant. Use p. 300 for help.
Modification
Function/advantage
Stem tuber; (potato)
Storage root (carrot)
Bulbs (onions)
Tendrils
Conclusions
1. Which kind of root system would more likely benefit a desert plant-a taproot or a fibrous root
system? Explain the benefits of EACH system to a plant living in the desert.
2. What is the difference between how a root handles water and how a stem handles it?
Because of this, how might the epidermis behave differently in roots and stems?