Download Roots, Stems and Leaves

Outside Structure
External Leaf Structure

Each leaf has a characteristic shape.
This includes the entire ‘picture’ of the
leaf.
The edge of the leaf is called the margin.
Most leaves also have visible veins.
You can use the shape, margin and vein
pattern of a leaf to identify plants.
Leaves

The arrangement of leaves on the
stem can also help to identify plant
types.
A leaf is connected to the stem by
the petiole, or the leaf stalk.
Stems

 Stems have 2 functions:
 1) Stems move water and
minerals from the roots
upward to the leaves
and move food (glucose)
from the leaves down to
the roots.
 Water is pulled up the stem
by water evaporating from
the leaves. Water is also
pulled up through capillary
action.
Stems

2) Stems support
the leaves,
flowers and
fruits/seeds.
Green stems also
manufacture food
just as leaves do
(they also have
chloroplasts)
External Stem Structure

Buds are short
stem tips,
composed of
resting leaves or
flowers or both.
Useful in the
identification of
plants.
Terminal Bud

 Terminal Bud –
 buds at the end
of stems.
Axillary Bud

 Axillary Bud – buds that grow on the side of the
stem.
Bud Scale Scar

 Bud Scale Scar- indicated
where a terminal bud
used to be located.
 On woody stems, the
distance between the
terminal bud and the
next bud scale scar
equals the growth
of the stem in one year.
Nodes and Internodes

 The stem is normally divided into nodes and internodes.
 The nodes hold buds which grow into one or more leaves,
inflorescence (flowers), conifer cones, roots, other stems
etc.
 The internodes are the
distance
from one node to
another.
 Add these labels to your
stem diagram.
Lenticels

 Lenticels are small holes that allow the stem to
breathe.
Twig Self Test

 http://www.biog11051106.org/demos/105/unit4/twigtest.html
Roots

 The functions of roots are:
 1) Absorb water and minerals from the soil.
 2) Anchor the plant in soil and keep it upright.
 Store food particles from the leaves.
Root Caps

 At the end of each root is a root cap.
 This root cap is protecting a layer directly behind it
called the meristem, an embryonic area.
 The embryonic area is in a state of constant growth
and pushes the root through the soil.
Root Hairs

 Growing out along the root are root hairs.
 These increase the surface area of the root and
therefore increase absorption of water and minerals.
Types of Roots

 Swollen Tap Root – 1 large tap root with many root
hairs. Stores materials from photosynthesis as starch.
 Example: Carrots and Parsnips
Types of Roots

 Primary Tap Root: Extends down the soil
surface in an unequal pattern. There is
no central tap root, rather many smaller
tap roots that extend in random directions.
Ex) Blazing
Star
Types of Roots

 Equal Tap Root: Very similar to a primary tap root
but the distribution of roots underneath the soil is
equal in all directions.
 Example: Sunflower
Types of Roots

 Fibrous Roots
 Create a network of fine, thin roots that extend deep
into the soil. No central root.
 Example: oats, palm trees, trees in later life.