Mr. Chapman
Biology 20
Recall the Difference Between
Plants Cells and Animal Cells...
 Remember that in addition to all of the cell structures
that animal cells have, plant cells have a few additional
structures.
 These structures are:
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Chloroplasts
Cell walls
Plastids
Large Central Vacuole
Plants are
Simple...
Plants have three
main organs, which
are made of three
types of tissues,
which are made of
three types of
cells...
Plant Cells
 Similar to animals, plants are made up of many types of
cells that are organized into tissues.
 There are 3 basic types of plant cells: Parenchyma cells,
collenchyma cells, and sclerenchyma cells.
Least specialized, most adaptable!
Parenchyma Cells
 The most abundant and least structurally specialized of
plant cells.
 They occur throughout plants and have many functions,
including photosynthesis, food storage, and general
metabolism.
 An important characteristic of parenchyma cells is that
they can divide and become specialized for various
functions.
A Parenchyma Cell:
Nothing too special about this guy...
Flexible plant cells that can change size and stretch. Where do you
think these cells would be found the most, and in what kinds of
plants?
Collenchyma cells
 Specialized for support while still allowing the plant to
grow. Most common in younger tissues of leaves and
shoots.
 Collenchyma cells have thick stretchable cell walls that
provide flexible support.
 The tough strings of celery stalk are made of collenchyma
cells.
Collenchyma Cells:
Thicker outer cell walls allow for some stretching in these cells while
still allowing the cells to grow...
Strong, tough, durable cells with TWO cells walls!
Sclerenchyma Cells:
 The strongest of the three types of cells, they have the thickets
cell walls out of any of them. This makes them very tough and
durable.
 Lignin makes the cells very tough and durable. These cells are
so tough and inflexible that they cannot grow with the rest of
the plant. As a result, they are typically found in the parts of
the plant that are no longer lengthening.
 Many sclerenchyma cells die after they reach maturity, and
their rigid cell walls are left behind in the plant as skeletal
support.
Sclerenchyma Cells Continued...
 Dead sclerenchyma cells form support structures for the
water conducting tissues of the plant.
 Sclerenchyma cells form a major part of fruit pits and the
hard outer shells of nuts.
 Responsible for the gritty texture of pears.
 Used by humans to make linen and rope.
Sclerenchyma Cell:
Comprehension Questions
 What are the three types of cells in a typical plant?
 Which of the cells is found in areas of the plant that are
growing, and why is this the case?
 What type of cell typically dies at maturity, and in what
portion of the plant is it typically found?
 Which type of plant cell is the least differentiated, but can
differentiate into different types of plant cells?
Three Different Kinds: Dermal, Ground, and Vascular
Dermal Tissue...
 Your body is covered with skin. Plants don’t have skin, but they
do have what is called dermal tissue.
 Dermal tissue covers the outside of the plant and protects it in
a variety of ways.
 Epidermis is made of live parenchyma cells that in the non-
woody parts of plants.
 Dermal tissue formed from dead parenchyma cells makes up
the outer bark of woody plants.
Dermal Tissue
Ground Tissue System
 Ground tissue is surrounded by the dermal tissue, and makes
up a great deal of the plant’s structure.
 The function of ground tissue is to provide support for the
plant, as well as to provide storage for materials inside the
stem and the roots.
 Ground tissue in the leaves is where chloroplasts are and
photosynthesis takes place, allowing plants to make their own
food.
 Parenchyma cells are the most common cells found in ground
tissue, but all three types are generally present.
Ground Tissue
Vascular Tissue System
 We have been learning previously in class about how
critical the vascular tissue is to plants.
 Vascular tissue transports water, mineral nutrients, and
organic compounds to the rest of the plant.
 Vascular tissue of a plant is made of hollow tubes that are
somewhat like the veins and arteries of humans. There
are two main types of vascular tissue in the body of a
plant:
Xylem
 Xylem is the vascular network in a plant that is
responsible for transporting water and dissolved mineral
nutrients up from the roots to the rest of the plant.
 Xylem, as we will learn, is mostly formed of dead
sclerenchyma cells that form a solid structure in the
center of the plant’s stem.
Phloem
 Phloem is the vascular network that is responsible for
carrying the products of photosynthesis down from the
leaves to the remainder of the plant.
 Recall that the products of photosynthesis are sugar and
oxygen. Phloem carries sugar down from the leaves to
the remainder of the plant.
 Xylem and phloem transport material through the plant
in different ways, as we will learn in the next section.
Xylem and Phloem
Comprehension Questions
 What are the three basic types of tissue that are found in a
plant?
 What are the main functions of ground tissue in the plant?
 Where are sclrenchyma cells typically found in a plant? What
do dead sclerenchyma cells form inside the plant?
 What are the two types of vascular tissue, and what is the
function of each one?