BOT3015L
Biology of Flowering Plants
Anatomy
Seedlings, Meristems, Stems,
and Roots
Presentation created by Danielle Sherdan
All photos from Raven et al. Biology of Plants except when otherwise noted
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and shoot meristem
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.
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and root meristem
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
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and shoot meristem
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
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
Root apical meristem
Meristem = group of perpetually
“embryonic” cells
Apical = at the tip (of the root,
the shoot, including laterals)
The rootcap and mucigel protect the
root apical meristem as it pushes
through the soil
Mucigel
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and shoot meristem
All cells of primary growth are from
one of three primary tissues
Diagram of major
parts of primary dicot
plant body
Ground tissue is
throughout the plant body
Ground tissue of
typical dicot root and shoot
Root
Shoot
Buttercup (Ranunculus)
Alfalfa (Medicago)
All cells are from one of three
primary tissues
Diagram of major
parts of primary dicot
plant body
Vascular tissue is
throughout the plant body
Vascular tissue of
typical dicot root
Root
Buttercup (Ranunculus)
Vascular tissue of
typical dicot shoot
Shoot
Alfalfa (Medicago)
All cells of primary growth are
from one of three primary tissues
Diagram of major
parts of primary dicot
plant body
Dermal tissue is throughout
the plant body
Ground tissue of
typical dicot root and shoot
Root
Shoot
Buttercup (Ranunculus)
Alfalfa (Medicago)
Specialized dermal cells in the shoot
The structure of the leaf and aspects of stomatal physiology
will be topics of study next week
Specialized epidermal cells
Venus flytrap
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and shoot meristem
Root Hairs—a special feature of roots (a)
Radish (Raphanus)
Bentgrass (Agrostis)
Root Hairs—a special feature of roots (b)
Cell Elongation
Cell Division
Root Hairs—a special feature of roots (c)
More than with shoots, elongation
growth is restricted to very near (~1.5
mm) the root tip; otherwise, elongation
would tear off lateral appendages.
Root hairs increase surface area.
Typical dicot root
Root
Buttercup (Ranunculus)
The endodermis
Casparian Strip—a band of
hydrophobic material (mostly
suberin) that is impregnated
in the wall, preventing
apoplastic transport.
From Outlaw’s lecture
The endodermis
Pathways for entry into xylem transport: all require that the
solute be transported into the symplast (because the apoplast
is discontinuous at the endodermis). Then, solutes
are excreted into the apoplast interior to the endodermis.
Apoplast
Symplast
From Outlaw’s lecture
Typical dicot root
Root
Buttercup (Ranunculus)
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
The pericycle
Ordinarily, lateral
roots arise in the
pericycle.
But roots can arise
adventitiously, too.
(Adventitious simply
means arising in an
unusual location.)
Salix (Salicaceae family)
From Outlaw’s lecture
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and shoot meristem
Mangrove (a dicot)
Support roots
in the marsh
habitat.
From Outlaw’s lecture
Interesting Examples
Orchid (a monocot)
Aerial roots
absorb water
from the air
and have a
multi-layered
epidermis for
protection and
reduced water
loss
Interesting Examples
Cross section of root
Epidermal layers
Flower pot plant
(an epiphyte)
Interesting Examples
Modified leaves form hollow containers that roots grow into
and that collect rainwater and debris. Many ants associate
with these plants, likely adding to nitrogen supply
Today
• Review seeds and the life cycle of plants
• Seed germination
• Roots and root meristem
• The three primary tissues
• Specialized cells in primary root tissues
• Interesting examples of root function and adaptations
• Shoot and shoot meristem
The shoot
What are the
functions of the
shoot?
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)
Apical Meristems both have the three primary
tissues
Root
Radish (Rafarus)
Shoot
Lilac (Syringa)
Lilac (Syringa)
Block
Diagram of
Typical Shoot
Apical
Meristem
Primary meristems give rise to primary tissues
Modified from Outlaw’s lecture
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
The main idea