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Monocot vs. Dicot
• Angiosperms are divided into monocots
and dicots
• As the zygote grows into the embryo, the
first leaves of the young plant develop and
are called cotyledons (seed leaves)
• Monocots have one cotyledon (corn, lily,
etc).
• Dicots have two cotyledons (bean, oak,
etc).
FEATURE
MONOCOTS
DICOTS
Cotyledons
1
2
Leaf venation
parallel
broad
Root system
Fibrous
Tap
Number of floral
parts
In 3’s
In 4’s or 5’s
Vascular bundle
position
Scattered
Arranged in a
circle
Herbaceous
Either
Woody or
herbaceous
Life cycles
From Outlaw’s lecture series
Floral structure
Angiosperm life cycle
Gametophytes
Today
From Outlaw’s lecture series
Monocot seed
development
typical monocot
(maize)
seed with ovary wall
(pericarp)
Monocots have one
cotyledon (scutellum in
grasses) that matures
during germination
Source of nutrition for seed
germination: endosperm
(compare to dicot)
Maize fruit and seed
Dicot seed development
immature
dicot - two cotyledons
mature
Three
tissue
systems:
Dermal
Vascular
Cortex or Ground
All cells of the primary
growth in dicots are
part of these three
systems and originate
at meristems
. . . A reminder that endosperm is formed in all angiosperms, but does not
persist in dicots. In dicots, cotyledons are the primary source of nutrients for
germination.
Seed germination
What causes a seed to resume growth?
What is growth?
Broadly, where do the energy and basic
elements required for growth come from?
What observations did you make while
germinating seeds?
Plants-In-Motion
Time-lapse videos of plant growth and response
Dicot germination and seedling
An example of epigeous (epi=above, geo=earth) germination
Dicot germination and seedling
An example of hypogeous (hypo=below, geo=earth) germination
Monocot
germination
and seedling
Root
the first structure to emerge from the
germinating seed
Typical dicot
Taproot
persists and
grows deep
into the ground
Typical monocot
Taproot does
not persist and
adventitious
roots originate
from the shoot
Notice the high surface volume: area ratio
Roots - Comparisons
Taproots:
Fibrous roots:
Typical of dicots,
primary root forms and
small branch roots
grow from it
In monocots mostly,
primary root dies,
replaced by new roots
from stem
Tap Root vs. Fibrous Root
What are the functions of roots?
From Outlaw lecture
Typical of a
dicot
Typical of a
monocot
Organization of the plant body
Meristem = group of perpetually
“embryonic” cells
Apical = at the tip (of the root,
the shoot, including laterals)
Diagram of major
parts of primary
dicot plant body
Vascular tissue is
throughout the plant body
Ground tissue of
typical dicot root and shoot
Root
Shoot
Buttercup (Ranunculus)
Alfalfa (Medicago)
Vascular tissue of
typical dicot root
Root
Buttercup (Ranunculus)
Dicot Root
Monocot Roots
Secondary Growth
(root)
Example cross section of the
dicot root in primary growth
The cambium (perpetually
meristematic layer between
xylem and phloem) divides
mitotically, producing either:
A secondary xylem cell to the
inside and a replacement
cambial cell.
OR
A secondary phloem cell to
the outside and a
Secondary growth rare in monocots
replacement cambial cell.
From Outlaw’s lecture
Roots – Structure and Development
Epidermis
Cortex
Monocot
Endodermis
Location of
Casparian strip
Primary phloem
Pericycle
Primary xylem
Pith
1250 µm
385 µm
Endodermis
Location of
Casparian strip
Endodermis
Eudicot
Primary xylem
Cortex
Primary phloem
Epidermis
Pericycle
48 µm
8 µm
Vascular tissue of
typical dicot shoot
Shoot
Alfalfa (Medicago)
Herbaceous dicot stem
Monocot stem
Primary tissues differently organized
in angiosperm shoots
Typical of dicots
Typical of monocots
Primary tissues differently organized in angiosperm shoots
Example dicot stem cross section
vascular bundles in ring with defined pith and cortex
Shoot
Alfalfa (Medicago)
Primary tissues differently organized in angiosperm shoots
Example monocot stem cross section
vascular bundles scattered
Maize (Zea)
Secondary Growth
(shoot)
Example cross section of the
dicot shoot in primary growth
The cambium (perpetually
meristematic layer between
xylem and phloem) divides
mitotically, producing either:
A secondary xylem cell to the
inside and a replacement
cambial cell.
OR
A secondary phloem cell to
the outside and a
replacement cambial cell.
From Outlaw’s lecture