Vascular plants are plants that have
specialized conducting tissue and are usually grouped as tracheophytes
and include the ferns, horsetails, angiosperms (flowering plants) and
gymnosperms (pine-like trees). Thallophytes (water type plants) and
bryophytes (mosses) do not have true roots, stems, and leaves and
possess no specialized system for the conduction of food and water from
one part of the plant to another. Plants that have a vascular system are
larger and able to cope with a "land situation." There are no
plants with a vascular system in a total water environment because the
water provides the nutrients the plants require, so they do not have to
"conduct" these substances.
Woody stems are mostly secondary
xylem (wood) surrounded by bark. The xylem may include heart-wood and
sap-wood. Heart-wood is dead and non-functional. The sap wood is
functional and has living parenchymal cells.
Give each group of children a
piece of celery (cross section) and have them place a drop of food
coloring on the top. The celery should show color only in small dots.
These are part of the xylem tissue that is responsible for water
Discuss with the students the
different types of specialized conducting cells of vascular plants namely, the phloem and the xylem.
Explain to students that phloem tissue conducts food produced in the
leaves to the rest of the plant while xylem tissue conducts water and
mineral salts from the roots. The xylem tissue also gives strength to
The xylem is the structure to the extreme left; and the phloem is the
center red area.
You can dramatically demonstrate the "power" of xylem
tissue by using a celery stalk and/or carnation. For the celery stalk
cut the bottom of the stalk (as in the diagram) and place one end in one
food color and the other in a different color. Within a day or so, the
water with the color will migrate upward and the celery will be two
colors. For the carnation, trim the stem and place it in colored water.
The water will migrate upward through the xylem tissue and color the
petals of the carnation.