Download AP Bio CVHS Ch 35 Plant Structure

Plant Structure Growth and
Development
Chapter 35
All Plants…
• multicellular, eukaryotic, autotrophic, alternation of generations
Alternation of Generations
Sporophyte (diploid)
• produces haploid
spores via meiosis
Gametophyte (haploid)
• produce haploid
gametes via mitosis
Fertilization
• joins two gametes to
form a zygote
Angiosperms
Monocots vs. Dicots
• named for the number
of cotyledons (seed leaf)
present on
the embryo of the plant
+ monocots
- orchids, corn,
lilies, grasses
+ dicots
- roses, beans,
sunflowers, oaks
Plant Morphology
Morphology (body form)
• 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
Plant Anatomy
Anatomy (internal structure)
• division of labor
+ cells differing in structure and function
- parenchyma, collenchyma, sclerenchyma (below)
- water- and food-conducting cells (next slide)
Parenchyma
St: “typical” plant cells
Fu: perform most metabolic functions
Collenchyma
St: unevenly thickened primary walls
Fu: provide support but allow growth
in young parts of plants
Sclerenchyma
St: hardened secondary walls
(LIGNIN)
Fu: specialized for support; dead
Plant cell types
Cell wall
Parenchyma cells
Collenchyma cells
Sclerenchyma cells
• Xylem
• Phloem
Plant cell types
WATER-CONDUCTING CELLS OF THE XYLEM
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Sieve-tube members:
longitudinal view
Vessel Tracheids
Pits
Companion cell
Sieve-tube
member
Sieve
plate
Tracheids and vessels
Nucleus
Vessel
element
Tracheids
Cytoplasm
Companion
cell
Water- and Food-conducting
Cells
Xylem (water)
Phloem (food)
• dead at functional maturity
• tracheids- tapered with pits
• vessel elements- regular tubes
• alive at functional maturity
• sieve-tube members- arranged
end to end with sieve plates &
Companion cells
Plant Tissues
Three Tissue Systems
• dermal tissue
+ epidermis (skin)
- single layer of cells that
covers entire body
- waxy cuticle/root hairs
• vascular tissue
+ xylem and phloem
- transport and support
• ground tissue
+ mostly parenchyma
- occupies the space b/n
dermal/vascular tissue
- photosynthesis, storage,
support
Plant Growth
Meristems
• perpetually embryonic tissues located at regions of growth
+ divide to generate additional cells (initials and derivatives)
- apical meristems (primary growth- length)
+ located at tips of roots and shoots
- lateral meristems (secondary growth- girth)
Roots
• 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)
Modified Roots
• Many plants have modified roots
(a) Prop roots
(a) Prop roots
(d) Buttress roots
(b) Storage roots
(b) Storage roots
(c) “Strangling” aerial
roots
(e) Pneumatophores
Primary Growth of Roots
Primary Growth of Roots
• apical meristem
+ root cap
+ three overlapping zones
- cell division
- elongation
- maturation
Stems
• A stem is an organ consisting of
– Nodes (point where leaf connects)
– Internodes (stem between nodes)
Modified Stems
(a)
Stolons
Storage leaves
(d)
Rhizomes
Stem
Node
Root
Bulbs
(c)
Tubers
Rhizome
Root
Buds
• An axillary bud
– Is a structure that has the potential to form a lateral shoot, or
branch
• A terminal bud
– Is located near the shoot tip and causes elongation of a young
shoot
Gardening tip:
Removing the terminal bud
stimulates growth of
axillary buds
Primary Growth in Shoots
Primary Growth in Shoots
• apical meristem (1, 7)
+ cell division occurs
+ produces primary meristems
- protoderm (4, 8)
- procambium (3, 10)
- ground meristem (5, 9)
• axillary bud meristems
+ located at base of
leaf primordia
• leaf primordium (2, 6)
+ gives rise to leaves
The leaf
Is the main photosynthetic organ of most vascular plants
Leaves generally consist of
Blade
Stalk
Petiole
Leaf Morphology
• In classifying angiosperms
– Taxonomists may use leaf morphology as a criterion
(a) Simple leaf
Petiole
Axillary bud
(b) Compound leaf.
Leaflet
Petiole
Axillary bud
(c) Doubly
compound leaf.
Leaflet
Petiole
Axillary bud
Modified Leaves
Tendrils
Spines
Storage leaves
Bracts
Reproductive leaves. The
leaves
of some succulents produce
adventitious
plantlets, which fall off the
leaf and
take root in the soil.
Leaf Anatomy
Epidermal Tissue
• upper/lower epidermis
• guard cells (stomata)
Ground Tissue
• mesophyll
+palisade/spongy
parenchyma
Vascular Tissue
• veins
+ xylem and phloem
Leaf Anatomy
Guard
cells
Key
to labels
Dermal
Ground
Stomatal pore
Vascular
Cuticle
Epidermal
cell
Sclerenchyma
fibers
50 µm
(b) 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
(a) Cutaway drawing of leaf tissues
Guard
cells
Vein
Air spaces
(c) Transverse section of a lilac
(Syringa) leaf (LM)
Guard cells
100 µm
The Three Tissue Systems:
Dermal, Vascular, and Ground
Dermal
tissue
Ground
tissue
Vascular
tissue
Dermal Tissue
–
•
•
•
Protects plant from:
Physical damage
Pathogens
H2O loss (Cuticle)
Vascular tissue
– Carries out long-distance transport of materials
between roots and shoots
– Consists of two tissues, xylem and phloem
Xylem
Phloem
Ground Tissue
– Includes various cells specialized for functions such as
storage, photosynthesis, and support
– Pith = ground tissue internal to the vascular tissue
– Cortex = ground tissue external to the vascular tissue
Secondary Growth
Lateral Meristems
• 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
The Vascular Cambium and Secondary Vascular Tissue
• The vascular cambium
– Is a cylinder of meristematic cells one cell thick
– Develops from parenchyma cells
2° Growth
• As a tree or woody shrub ages
– 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
Cork Cambium
Periderm
• protective coat of
secondary plant body
+ cork cambium and
dead cork cells
- bark
• cork cambium produces
cork cells