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Unit B: Plant Anatomy
Lesson 1:
Understanding Root Anatomy
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Vocabulary
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Apical meristem
Epidermis
Fibrous root system
Primary root
Root cap
Root hairs
Secondary roots
Taproot system
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What Are the Functions of
a Plant’s Roots?
 A plant’s health is directly
related to its roots
 Weak and diseased roots
decrease a plant’s health
 Roots need to continuously
grow in order to stay
healthy
A pot bound plant in
need of transplanting
Courtesy of Delmar Publishing
 This is why plants become
pot-bound: the roots start
growing out of the pot
because it is too small
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Functions of a Root System
 1. Absorb water and
minerals from the
environment
 2. Anchor the plant in
the ground
 3. Store food that has
been made in the
leaves by
photosynthesis
 Can be used later by the
plant to grow and survive
Taraxacum officinale – the
common dandelion
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Courtesy of Wm. C. Brown Publishers
What Are the Parts of a
Root?
 When a seed
germinates, the first
structure to appear is the
root, or radicle
 A. It becomes the
primary root
 Usually the most
important root in some
plants
Cotyledon
Radicle = Primary
root; notice all the
root hairs
Courtesy of McGraw Hill
 B. Other roots branch out
from the primary root;
called secondary
roots
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 C. The apical meristem,
found at the root tip, is
where new cells
develop
Vascular
cylinder
(xylem &
phloem)
Cortex
(food
storage)
Epidermis
 It is covered by the root
cap – protects it from
damage as it passes
through coarse soil
particles
Apical
meristem
Root Cap
Courtesy of Dorling Kindersley, Inc.
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Epidermis
 D. The surface of the root
is protected by skin
cells called the
epidermis
 Where water and
minerals enter the root
by osmosis & diffusion
 Can grow long, hair like
projections called root
hairs
 They greatly increase the
surface area of the root to
allow more water intake
Courtesy of Delmar Publishing
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Regions of Cell
Development
Region of
Maturation
Region of
Elongation
Root
Cap
Region of
Cell Division
Apical
meristem
 Notice that cell
division occurs
at the tip of the
root
 Older cells are
found farther
away from the
root tip
Courtesy of McGraw
Hill Publishers
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What Are the Two Types
of Root Systems?
 Plant root systems are organized in two
basic ways; It has to do with primary
and secondary roots
 A. A root system comprising one main
primary root and many secondary roots
branching off the primary root is called a
taproot system
 Their roots reach far into the ground; they
can be several feet long
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Examples of Taproots
Carrot
Beet
Sweet potato
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Courtesy of Wm. C. Brown Publishers
Tap Root Systems
 Advantages
 Penetrate deeper into the soil
 Obtain water from lower levels
 Anchor the plant
 Disadvantages
 Difficult to remove/harvest plants
 Do not stabilize the soil well
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 B. A system which has no
dominant primary root but is
made of many primary and
secondary roots of similar
size is called a fibrous root
system
 Ex. Grasses, Magnolia,
Rhododendron, Euonymus
 The roots are smaller, shorter
and more compact; They usually
never grow below the first 6-12
inches of soil
Fibrous root system of
grass
Courtesy of McGraw Hill Publishing
 These roots form a large network
underground
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Fibrous root system
 Advantages
 Shallower, thus respond more quickly to
fertilization/irrigation
 Stabilize the soil better
 Disadvantages
 Less drought resistant
 Tend to get exposed during cultivation
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What Does a Healthy Root
System Look Like?
 A healthy root system is white or nearly white
in color and smells fresh, or earthy
 If roots are black, brown, or dark orange and
smell rotten or sour, the root system is having
some problems
 Watering a plant properly is one of the most
important ways to keep the root system healthy
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Healthy Roots
Unhealthy Roots
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 If the plants are grown in pots, be sure that
there are drainage holes in the bottom to allow
excess water to drain
 Soak the pot until the growing medium is
saturated and water drips out of the drainage
holes
 This encourages the roots to grow through
the entire pot
 Allow the pot to dry out slightly between
watering
 Watering too frequently is a common cause
of root death
 Medium that is kept wet has limited air
exchange; the root tissues die for lack of air
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Recognize the economical
importance of roots.
 Roots impact society in many different ways
 The term root crops refers to any edible
underground plant structure, but many root
crops are actually stems, such as potato tubers
 Edible roots include cassava, sweet potato,
beet, carrot, rutabaga, turnip, parsnip, radish,
yam and horseradish. Spices obtained from
roots include and licorice. sassafras, angelica,
sarsaparilla
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 Sugar beet is an important source of
sugar. The fish poison and insecticide
rotenone is obtained from roots of
Lonchocarpus spp.
 Important medicines from roots are
ginseng, aconite, ipecac, gentian and
reserpine
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 Several legumes that have nitrogenfixing root nodules are used as green
manure crops, which provide nitrogen
fertilizer for other crops when plowed
under.
 Specialized bald cypress roots, termed
knees, are sold as souvenirs, lamp bases
and carved into folk art. Some people
have used the flexible roots of white
spruce for basketry.
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Summary
 What are the three functions of a root?
 What is another name for a primary root?
 In the tip of the root, what kinds of cells
are the only ones that divide?
 What is the epidermis and what is its
function?
 Where do root hairs grow from?
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Summary
 Why does a plant have to have numerous root
hairs instead of just two or three?
 Pretend you are a water molecule and you
need to get into the center of the root. What
are all the layers you must go through before
reaching the center?
 Describe the functions of the xylem and
phloem.
 Where is food stored in the root?
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