Transcript PowerPoint

Understanding Root Anatomy
Next Generation Science/Common Core Standards Addressed!
 HS‐LS1‐2. Develop and use a model to illustrate the hierarchical organization of
interacting systems that provide specific functions within multicellular organisms.
[Clarification Statement: Emphasis is on functions at the organism system level such
as nutrient uptake, water delivery, and organism movement in response to neural
stimuli. An example of an interacting system could be an artery depending on the
proper function of elastic tissue and smooth muscle to regulate and deliver the
proper amount of blood within the circulatory system.] [Assessment Boundary:
 HS‐LS2‐3. Construct and revise an explanation based on evidence for the
cycling of matter and flow of energy in aerobic and anaerobic conditions.
[Clarification Statement: Emphasis is on conceptual understanding of the role
of aerobic and anaerobic respiration in different environments.][Assessment
Boundary: Assessment does not include the specific chemical processes of
either aerobic or anaerobic respiration.]
Agriculture, Food, and Natural
Resource Standards Addressed
 PS.02.02.02.a. Identify and summarize the
components, the types and the functions of plant
roots.
Bell Work
Terms!
 Apical meristem
 Epidermis
 Fibrous root system
 Primary root
 Root cap
 Root hairs
 Secondary roots
 Taproot system
Interest Approach
Take a look at this plant that I have just knocked out
of its pot.
How is the soil being held in place?
What can you see in the soil and on the roots?
Take a look at the roots under a stereomicroscope.
Draw a picture of what you see.
Why do the roots look hairy?
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
This is why plants become potbound: the roots start growing out
of the pot because it is too small
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
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

Cotyledon
Radicle = Primary
root; notice all the
root hairs
Usually the most important
root in some plants
 B. Other roots branch out
from the primary root;
called secondary roots
 C. The apical
meristem, found at
the root tip, is where
new cells develop

It is covered by the
root cap – protects
it from damage as it
passes through
coarse soil particles
 D. The surface of the root is
Epidermis
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

Courtesy of Delmar Publishing
They greatly increase the
surface area of the root to
allow more water intake
 There are three major zones of root development
 1. Region of Cell Division – this is where the cells start to
divide through mitosis

Remember, this is where the apical meristem is located
 2. Region of Elongation – in this area just above the
apical meristem, cells become longer and wider

This action helps to push the root tip through the soil
 3. Region of Maturation – at this point, the cells become
specialized, or differentiated, taking on specific primary
functions

For example, the development of root hairs, xylem, phloem,
etc.
Regions of Cell Development
Region of
Maturation
Region of
Elongation
Root
Cap
 Notice that cell
division occurs
at the tip of the
root
 Older cells are
found farther
away from the
Region of
Cell Division
Apical
meristem
root tip
Courtesy of McGraw
Hill Publishers
 There are several other layers of cells found within
the root
 A. Cortex – this is where the root stores the food
produced by the leaves; it is made out of parenchyma
tissue
 B. Endodermis – the inner boundary of the cortex; one
cell layer thick; controls the movement of water and
minerals into the xylem and phloem
 C. Pericycle – a layer found inside the endodermis
which may produce lateral roots; also produces vascular
cambium in dicots
 D. Vascular cylinder, or stele – forms the central cylinder
of the root; it is made out of two secondary transport
tissues


1. Xylem – carries the water taken in by the root hairs and
epidermis up the plant to the stems and leaves
2. Phloem – carries the food produced by the leaves down to
the roots to be stored in the cortex
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


Ex. Carrot, Parsnip, Oak
Their roots reach far into the ground; they can be several
feet long
Examples of Taproots
Carrot
Beet
Sweet potato
Courtesy of Wm. C. Brown Publishers
 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


Fibrous root system of
grass
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
 These roots form a large network
underground
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
 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.
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?
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?
The End