Download Plant Form and Function

3/1/2016
 Morphology
form)

Plant biology, perhaps the oldest branch of science, is
driven by a combination of curiosity and need
curiosity about how plants work
need to apply this knowledge judiciously to feed, clothe,
and house a burgeoning human population.
(body
shoot and root systems
inhabit two
environments
• shoot (aerial)
 stems, leaves, flowers
• root (subterranean)
 taproot, lateral roots

vascular tissues
transport materials
between roots and
shoots
• xylem/phloem
• A Root
– Is an organ that anchors the
vascular plant
– Absorbs minerals and water
– Often stores organic
nutrients
– Taproots found in dicots and
gymnosperms
– Lateral roots (Branch roots
off of the taproot)
– Fibrous root system in
monocots (e.g. grass)
(b) Storage roots
(a) Prop roots
(c) “Strangling” aerial
roots
(d) Buttress roots

A stem is an organ consisting of
– Nodes (could be opposite or
alternate)
– Internodes
(e) Pneumatophores
(a)
Stolons
Storage leaves
(d)
Rhizomes
Stem
Node
Root
Bulbs
(c)
Tubers
Rhizome
Root
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 An
 The
axillary bud
form a lateral shoot, or branch
A
leaf
• Is the main photosynthetic organ of most
• Is a structure that has the potential to
vascular plants
terminal bud
 Leaves
• Is located near the shoot tip and causes
generally consist of
• Blade
elongation of a young shoot
• Stalk
• Petiole
Gardening tip:
Removing the terminal
bud stimulates growth of
axillary buds
classifying
angiosperms
Three Tissue Systems
 In
– Taxonomists may
use leaf
morphology as a
criterion

Petiole
Axillary bud
(b) Compound leaf.
dermal tissue
• epidermis (skin)
 single layer of cells that covers
entire body
 waxy cuticle/root hairs
(a) Simple leaf

vascular tissue

ground tissue
Leaflet
• xylem and phloem
 transport and support
Petiole
Axillary bud
• mostly parenchyma
 occupies the space b/n
dermal/vascular tissue
 photosynthesis, storage, support
(c) Doubly
compound leaf.
Leaflet
Petiole
Axillary bud
 Carries

Protects plant from:
• Physical damage
• Pathogens
• H2O loss (Cuticle)
out long-distance
transport of materials
between roots and shoots
 Consists of two tissues
• xylem
• phloem
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



•
•
•

Any tissue that isn’t
dermal or vascular
Includes various cells
specialized for storage,
photosynthesis, and
support
Pith = ground tissue
internal to the vascular
tissue
Cortex = ground tissue
external to the vascular
tissue

Xylem (water)
dead at functional maturity
tracheids- tapered with pits
vessel elements- regular
tubes
Vessel
Parenchyma
St: “typical” plant cells. Most
abundant
Fu: perform most metabolic
functions
Ex: fleshy tissue of most fruit

•
•
WATER-CONDUCTING CELLS OF THE XYLEM
Anatomy (internal structure)
• division of labor
• cells differing in structure and function – 5 types
• parenchyma, collenchyma, sclerenchyma
Collenchyma
Sclerenchyma
St: grouped in cylinders; thick
Fu: provide support but allow growth
in young parts of plants
Ex: celery
St: hardened secondary walls
Fu: specialized for support; dead
Ex: fibers (hemp/flax)
 Meristems
• perpetually embryonic tissues located at regions of growth
• divide to generate additional cells (initials and derivatives)
• apical meristems (primary growth- length)
Phloem (food)
alive at functional maturity
sieve-tube members arranged
end to end with sieve plates
 located at tips of roots and shoots
• lateral meristems (secondary growth- girth)
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Sieve-tube members:
longitudinal view
Tracheids
Pits
Companion cell
Sieve-tube
member
Sieve
plate
Tracheids and vessels
Nucleus
Vessel
element
Tracheids
Cytoplasm
Companion
cell
Cortex
Vascular cylinder
Epidermis
Key
to labels
Primary
of Roots
Growth

• Includes apical
meristem
 Plants grow in length
(roots and shoots)


Zone of elongation

Zone of maturation
• Elongation of cells
• Cell differentiation
• Cell become functionally
Dermal
Root hair
Zone of
differentiation
Ground
Vascular
• New cells produces
• Root cap is located in
Zone of cell division
• Includes apical meristem
• New cells produces
• Root cap is located in root
Zone of cell division
root

Zone of elongation

Zone of maturation
Zone of
elongation
• Elongation of cells
• Cell differentiation
• Cell become
Apical
meristem
functionally mature
Zone of cell
division
Root cap
mature
100 µm
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Primary Growth
in Shoots

Epidermal Tissue
• upper/lower epidermis
• guard cells (stomata)
 Apical
meristem (1,
7)
 Located at buds of
shoots
 Site of cell division
that allows plant to
grow in length

Ground Tissue
• Mesophyll
• palisade/spongy
parenchyma

Vascular Tissue
• Veins
• xylem and phloem
Leaf Anatomy
Guard
cells
Key
to labels
Dermal
Ground
Vascular
Cuticle
Stomatal pore
Epidermal
cell
Sclerenchyma
fibers
50 µm
(b) Surface view of a spiderwort
(Tradescantia) leaf (LM)
Stoma
Upper
epidermis
Palisade
mesophyll
Bundlesheath
cell
Lateral Meristems
Spongy
mesophyll
Lower
epidermis
Cuticle
Guard
cells
Xylem
Phloem
(a) Cutaway drawing of leaf tissues
Vein
Guard
cells

The vascular
cambium

As a tree or woody
shrub ages
Vein
Air spaces
Guard cells
(c) Transverse section of a lilac
(Syringa) leaf (LM)
100 µm
• vascular cambium
+ produces secondary xylem/phloem (vascular tissue)
• cork cambium
+ produces tough, thick covering (replaces epidermis)
• secondary growth
+ occurs in all gymnosperms; most dicot angiosperms
– Develops from
parenchyma cells
• The older layers of
secondary xylem, the
heartwood, no longer
transport water and
minerals

The outer layers,
known as sapwood
• Still transport materials
through the xylem
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 Periderm -
protective coat of
secondary plant
body
 cork cambium
produces cork cells
 secondary growth
commences farther
down the shoot
 transforms older
regions first
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