BACKGROUND:
A plant cell is different from an animal
cell in that it possesses a cell wall, chloroplasts, large vacuoles, and
starch grains (amyloplasts). The cell wall is the outer wall that surrounds
plant cells. Chloroplasts contain chlorophyll and function during
photosynthesis. Vacuoles store food molecules, water and salts. Starch grains
are used to store starch which will provide food for the plant. Plants are
made up of many cells that work together to form tissues. There are many types
of plant tissues.
The growth of plants occurs in the
meristematic tissues. In these tissues the cells are actively dividing, and
new cells are continually being produced. Apical meristems are located in
roots and stems. Vascular cambium is a meristematic tissue located between the
bark and wood (or phloem and xylem). Different types of plants have different
types of tissues. Leaf tissue has an upper and lower epidermis which forms a
relatively waterproof layer because the cuticle protects the inner cells.
Cutin, a fatty material, is secreted by the epidermal cells and forms a waxy
layer. There are also guard cells between which are located pores called
stomata that are used when the plant transpires and in photosynthesis. Between
the epidermal layers is the mesophyll which is divided into the palisade layer
and a mass of loosely arranged, irregularly shaped cells called the spongy
layer. The vascular bundles of the leaf are enclosed in one or more layers of
compactly arranged cells forming the bundle sheath. The xylem and phloem which
form a way for cells to move nutrients and water up and down a plant is a
complex permanent tissue. The xylem is the principal water conducting tissue
in plants and the phloem is the principal food conducting tissue.
PROCEDURE:
- On the worksheet students are to color
the stated tissue by finding the tissues on the diagrams. Discuss with
students the various parts of a plant. The key part is to illustrate the many
components, not to memorize them.
- Please note that these pictures are the
"ideal" plant. Have students look back at Human Biology (4A) Post
and Human Biology (5A) Pre so they can compare plant and human tissues.
They should notice that there are few similarities between plant and animal
tissue. But then, a plant and a human are quite different!
