Transcript Plant Structure

Reproductive shoot (flower)
Terminal bud
Node
Internode
Terminal
bud
Vegetable
shoot
Leaf
Shoot
system
Blade
Petiole
Axillary
bud
Stem
Taproot
Lateral roots
Root
system
Roots
 Functions of roots:
 Anchoring the plant
 Absorbing minerals and water
 Often storing organic nutrients
Root Hairs
Prop roots.
Storage roots.
“Strangling” aerial roots.
Buttress roots.
Pneumatophores.
Stems
 Stem
 Nodes

points at which leaves are attached
 Internodes

stem segments between nodes
 axillary bud
 has the potential to form a lateral shoot, or branch
 terminal bud
 located near the shoot tip
 causes elongation of a young shoot
Stolons.
Storage leaves
Stem
Roots
Bulbs.
Tubers.
Rhizomes.
Node
Rhizome
Root
Leaves
 Leaf
 main photosynthetic organ
 consist of


A flattened blade and a stalk
petiole
 Monocots
 parallel veins
 Eudicots
 branching veins
Simple leaf
Petiole
Axillary bud
Leaflet
Compound leaf
Petiole
Axillary bud
Doubly compound leaf
Leaflet
Petiole
Axillary bud
Tendrils.
Spines.
Storage leaves.
Bracts.
Reproductive
leaves.
Plant Tissues
 Dermal
 Epidermis (nonwoody)
 Periderm (woody)
 Vascular
 Xylem


Water & dissolved minerals
Upward from roots to shoots
 Phloem


organic nutrients
Transports from location made to where they are needed
 Ground tissues
 Storage, photosynthesis, & support
Dermal
tissue
Ground
tissue
Vascular
tissue
 Some major types of plant cells:
 Parenchyma
 Collenchyma
 Sclerenchyma
 Water-conducting cells of the xylem
 Sugar-conducting cells of the phloem
WATER-CONDUCTING CELLS OF THE XYLEM
PARENCHYMA CELLS
Vessel
Parenchyma cells in Elodea
leaf, with chloroplasts (LM)
Tracheids
100 µm
60 µm
Pits
COLLENCHYMA CELLS
80 µm
Cortical parenchyma cells
Tracheids and vessels
(colorized SEM)
Vessel
element
Vessel elements with
perforated end walls
Tracheids
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Collenchyma cells (in cortex of Sambucus,
elderberry; cell walls stained red) (LM)
Sieve-tube members:
longitudinal view
(LM)
SCLERENCHYMA CELLS
5 µm
Companion
cell
Sclereid cells in pear (LM)
Sieve-tube
member
Plasmodesma
25 µm
Sieve
plate
Cell wall
Nucleus
Cytoplasm
Companion
cell
30 µm
15 µm
Fiber cells (transverse section from ash tree) (LM)
Sieve-tube members:
longitudinal view
Sieve plate with pores (LM)
Meristems
 Apical meristems
 located at the tips of roots and in the buds of shoots
 elongate shoots and roots

primary growth
 Lateral meristems
 add thickness to woody plants

secondary growth
 two types:


vascular cambium
 adds layers of vascular tissue
 secondary xylem (wood)
 secondary phloem
cork cambium
 replaces the epidermis with periderm
 thicker and tougher
Primary growth in stems
Shoot apical
meristems
(in buds)
Epidermis
Cortex
Primary phloem
Primary xylem
Vascular
cambium Lateral
meristems
Cork
cambium
Pith
Secondary growth in stems
Periderm
Cork
cambium
Pith
Cortex
Primary
phloem
Primary
xylem
Root apical
meristems
Secondary
xylem
Secondary
phloem
Vascular cambium
Terminal bud
Bud scale
Axillary buds
Leaf scar
This year’s growth
(one year old)
Node
Stem
Internode
One-year-old side
branch formed
from axillary bud
near shoot apex
Leaf scar
Last year’s growth
(two years old)
Scars left by terminal
bud scales of previous
winters
Growth of two
years ago (three
years old)
Leaf scar
Primary Growth of Roots
 Zone of cell division
 Zone of elongation
 Zone of maturation
Cortex
Vascular cylinder
Epidermis
Key
Root hair
Dermal
Zone of
maturation
Ground
Vascular
Zone of
elongation
Apical
meristem
Root cap
100 µm
Zone of cell
division
Apical meristem
Leaf primordia
Developing
vascular
strand
Axillary bud
meristems
0.25 mm
Phloem
Xylem
Sclerenchyma
(fiber cells)
Ground
tissue
Ground tissue
connecting
pith to cortex
Pith
Epidermis
Key
Cortex
Epidermis
Vascular
bundles
Dermal
Vascular
bundles
Ground
1 mm
A eudicot (sunflower) stem. Vascular bundles form
a ring. Ground tissue toward the inside is called
pith, and ground tissue toward the outside is called
cortex. (LM of transverse section)
Vascular
1 mm
A monocot (maize) stem. Vascular bundles are scattered
throughout the ground tissue. In such an arrangement,
ground tissue is not partitioned into pith and cortex. (LM
of transverse section)
Key
to labels
Guard
cells
Dermal
Stomatal pore
Ground
Vascular
Cuticle
Sclerenchyma
fibers
Epidermal
cells
50 µm
Surface view of a spiderwort
(Tradescantia) leaf (LM)
Stoma
Upper
epidermis
Palisade
mesophyll
Bundlesheath
cell
Spongy
mesophyll
Lower
epidermis
Guard
cells
Cuticle
Vein
Xylem
Phloem
Cutaway drawing of leaf tissues
Guard
cells
Vein
Air spaces
Guard cells
100 µm
Transverse section of a lilac
(Syringa) leaf (LM)
Morphogenesis and Pattern Formation
 Pattern formation
 development of specific structures in specific locations
 determined by positional information


signals indicating to each cell its location
Ex. Polarity