Transcript You Light Up My Life - Dr. Annette M. Parrott

Plant Tissues
Angiosperms – flowering plants
• The angiosperms are seed-bearing
vascular plants
• In terms of distribution and diversity, they
are the most successful plants on Earth
• The structure and function of this plant
group help explain its success
Monocots and Dicots – same
tissues, different features
1 cotyledon
4 or 5 floral
parts
3 floral
parts
Parallel veins
1 pore
Vascular
bundles
in ring
2 cotyledons
Netlike veins
3 pores
Vascular
bundles
dispersed
Flowering
Plant Life
Cycle
Diploid
Double fertilization
Haploid
pollination
Two
sperms
enter
ovule
Meiosis
microspores
Female gametophyte
Meiosis
Mitosis
without
cytoplasmic
division
Plant Life Histories
• Annuals complete life cycle in one growing season
• Biennials live for two seasons; flowers form in second
season
• Perennials grow and produce seeds year after year
Meristems – Where Tissues Originate
• Regions where cell
divisions produce plant
growth
• Apical meristems
– Lengthen stems and roots
– Responsible for primary
growth
Leaves
Internode
Axillary bud at node
• Lateral meristems
– Increase width of stems
– Responsible for secondary
growth
Longitudinal section of
Apical Meristems
Lengthen shoots and roots:
StemAM and RootAM
activity at
meristems
Cells that form at apical
meristems:
protoderm  epidermis
ground meristem  ground
tissues
procambium  primary
vascular tissues
new cells
elongate
and start to
differentiate
into primary
tissues
Lateral Meristems
Increases girth of older roots and stems
Cylindrical arrays of cells
vascular cambium  secondary vascular tissues
periderm  cork cambium
thickening
Plant Tissue
Systems
• Ground tissue
system
• Vascular tissue
system
• Dermal tissue
system
EPIDERMIS
VASCULAR TISSUES
GROUND TISSUES
SHOOT SYSTEM
ROOT SYSTEM
Ground Tissue
• fills space b/t dermis & vascular
Parenchyma:
Primary
metabolic
(photosynthesis)
function
– Found in roots, stems & leaves
– Least specialized, thin flexible walls, don’t divide unless
specializing, respire, store food & water
Schlerenchyma: support w/ thick 2o well strengthened
by lignin
– Found in stems & leaves
generally lack protoplasts
– Very rigid cell wall, dead at maturity, cannot lengthen
scaffolding “fibers” & “Sclereids”
Collenchyma:
child support
– Found in stems and leaves
– Grow and elongate with stems and leaves they support,
flexible in young parts of plant
Morphology of three simple tissue types
parenchyma
collenchyma
sclerenchyma
Parenchyma: A Simple Tissue
• Comprises most of a plant’s soft primary
growth
• Cells are pliable, thin walled, many sided
• Cells remain alive at maturity and retain
capacity to divide
• Mesophyll is a type of parenchyma that
contains chloroplasts
Collenchyma: A Simple Tissue
• Specialized for support for primary tissues
• Cells are elongated, with walls (especially
corners) thickened with pectin
• Makes stems strong but pliable
• Cells are alive at maturity
Sclerenchyma: A Simple Tissue
• Supports mature plant parts
• Protects many seeds
• Cells have thick, lignified walls and are dead at
maturity
• Two types:
– Fibers: Long, tapered cells
– Sclereids: Stubbier cells
Simple Tissues
Made up of only one
type of cell
Parenchyma
Collenchyma
Sclerenchyma
Complex Tissues
Composed of a mix of cell types
Xylem
Phloem
Epidermis
Vascular Tissue
Phloem: Phood conduction, carries products of photosynthesis to
non-photo cells
– Found in roots, stems, leaves
– Sieve cells, albuminous cells, companion cells, parenchyma
– Gymnospersm: sieve, angiosperms, sieve-tube members, connected
vertically by sieve plates
– Alive at maturity
Xylem:
–
–
–
–
–
provides water & ion transport from roots to leaves
Vessel elements, tracheids, fibers, wood parenchymal
tracheids & vessel members, thick w/ secondary wall with lignin
Dead at maturity
Seedless vascular & gymnosperms have tracheids w/ tapered ends
Angiospersm have both tracheids and vessel members wh are
continuous
Xylem
• Conducts water
and dissolved
minerals
• Conducting cells
are dead and
hollow at maturity
tracheids
vessel
member
Phloem: A Complex Vascular
Tissue
sieve plate
• Transports sugars
• Main conducting
cells are sievetube members
• Companion cells
assist in the
loading of sugars
sieve-tube
member
companion
cell
Epidermis:
A Complex Plant Tissue
- Covers and protects plant
surfaces
- Secretes a waxy,
waterproof cuticle
- In plants with secondary
growth, periderm replaces
epidermis
Epiderm
• protection, increase absorption area in roots,
reduces H2O loss in stem & leaves,
• Regulates gas exchange in leaves
Signaling between Plants and Pathogens
Shoot and Root
Systems
Shoot system
- produces sugars by
photosynthesis
Shoot
System
- carries out reproduction
Root system
- anchors the plant
- penetrates the soil and
absorbs water and minerals
- stores food
Root
System
Shoot and root
systems are
interdependent
water &
minerals
sugar
SHOOT SYSTEM
ROOT SYSTEM
shoot apical
meristem
Shoot
Development
cortex
procambrium
protoderm procambrium
pith
ground meristem
primary xylem
primary phloem
Roots also have meristems
Leaf Gross Structure
DICOT
MONOCOT
petiole
axillary
bud
blade
node
sheath
blade
node
Adapted for Photosynthesis
• Leaves are usually thin
– High surface area-to-volume ratio
– Promotes diffusion of carbon dioxide in,
oxygen out
• Leaves are arranged to capture sunlight
– Are held perpendicular to rays of sun
– Arrange so they don’t shade one another
Leaf Structure
UPPER
EPIDERMIS
cuticle
PALISADE
MESOPHYLL
xylem
SPONGY
MESOPHYLL
phloem
LOWER
EPIDERMIS
O2
CO2
one stoma
Mesophyll:
Photosynthetic Tissue
• A type of parenchyma tissue
• Cells have chloroplasts
• Two layers in dicots
– Palisade mesophyll
– Spongy mesophyll
Collenchyma
Parenchyma
Leaf Veins: Vascular Bundles
• Xylem and phloem –
often strengthened with fibers
• In dicots, veins are netlike
• In monocots, they are parallel
Internal Structure of a
Dicot Stem
- Outermost layer is epidermis
- Cortex lies beneath epidermis
- Ring of vascular bundles
separates the cortex from the pith
- The pith lies in the center of the
stem
Internal
Structure
of a
Monocot
Stem
• The vascular bundles
are distributed
throughout the ground
tissue
• No division of ground
tissue into cortex and
pith
Dicots
Monocots
Ground tissue
system
Dermal tissue
system
Vascular tissue
system
Dicots and Monocots have different stem and root anatomies
Stems
Monocot stems differ
from dicot stems in
that they lack
secondary growth
• No vascular cambium
nor cork cambium
• Stems usually
uniform in diameter
• Scattered vascular
bundles (not in a ring
like dicot stems)
The Translocation of Phloem
•
•
•
the process of moving
photosynthetic product through the
phloem
In angiosperms, the specialized cells
that transport food in the plant are
called sieve-tube members,
arranged end to end to form large
sieve tubes
Phloem sap is very different from
xylem sap
– sugar (sucrose) can be concentrated
up to 30% by weight
•
Phloem transport is bidirectional
– Phloem moves from a sugar source
(a place where sugar is produce by
photosynthesis or by the breakdown
of sugars) to a sugar sink (an organ
which consumes or stores sugar)
– What are some organs which would
be sugar sinks?
Transport in Plants: The Pressure Flow Model
Transpiration Pull
Root Systems
Root Structure
• Root cap covers tip
• Apical meristem produces
the cap
• Cell divisions and
elongation at the apical
meristem cause the root to
lengthen
• Farther up, cells
differentiate and mature
root apical
meristem
root cap
Primary Root Growth
Root Cap
•Secretes polysaccharide slime that lubricates the soil
•Constantly sloughed off and replaced
Apical Meristem
•Region of rapid cell division of undifferentiated cells
•Most cell division is directed away from the root cap
Quiescent Center
•Populations of cells in apical meristem which reproduce much more
slowly than other meristematic cells
•Resistant to radiation and chemical damage
•Possibly a reserve which can be called into action if the apical meristem
becomes damaged
The Zone of Cell Division - Primary Meristems
•Three areas just above the apical meristem that continue to divide for
some time
•Protoderm
•Ground meristem
•Procambium
The Zone of Elongation
•Cells elongate up to ten times their original length
•This growth pushes the root further downward into the soil
The Zone of Maturation
•Region of the root where completely functional cells are found
Internal Structure of a Root
• Outermost layer is epidermis
• Root cortex is beneath the epidermis
• Endodermis, then pericycle surround
the vascular cylinder
• In some plants, there is a central pith
epidermis
endodermis
cortex
pericycle
root hair
phloem
xylem
Root Anatomy - Dicot Roots
Epidermis
•
Dermal tissue
•
Protection of the root
Cortex
•
Ground tissue
•
Storage of photosynthetic products
•
Active in the uptake of water and minerals
Endodermis
•
cylinder once cell thick that forms a boundary between the
cortex and the stele contains the casparian strip,
Pericycle
•
found just inside of the endodermis
•
may become meristematic
•
responsible for the formation of lateral roots
Vascular Tissue
•
Xylem and Phloem
Root Anatomy - Monocot Roots
Epidermis
•
Dermal tissue
•
Protection of the root
Cortex
•
Ground tissue
•
Storage of photosynthetic products
•
Active in the uptake of water and minerals
Endodermis
•
cylinder once cell thick that forms a boundary between the
cortex and the stele even more distinct than dicot counterpart
contains the casparian strip,
Pericycle
•
monocot roots rarely branch, but can, and this branch will
originate from the pericycle
Vascular Tissue
•
Xylem and Phloem
•
Forms a ring near center of plant
Pith
•
Center most region of root
Root Hairs and Lateral Roots
• Both increase the surface area of
a root system
• Root hairs are tiny extensions of
epidermal cells
• Lateral roots arise from the
pericycle and must push through
the cortex and epidermis to reach
the soil
•
Root of a single rye plant (fibrous system) measure
and counted 6400 roots w/ 12.5 million root hairs =
250 km, dist from Memphis, TN to Atlanta, GA
new
lateral
root
Symplastic Movement
• Movement of water and solutes through the continuous
connection of cytoplasm (though plasmodesmata)
• No crossing of the plasma membrane (once it is in the
symplast)
Apoplastic Movement
• Movement of water and solutes through the cell walls and the
intercellular spaces
• No crossing of the plasma membrane
• More rapid - less resistance to the flow of water
Secondary Growth
• Occurs in perennials
• A ring of vascular cambium produces
secondary xylem and phloem
• Wood is the accumulation of these
secondary tissues, especially xylem
Secondary Growth
The Plant Body: Secondary Growth: The Vascular
Cambium
Woody Stem
periderm (consists of
cork, cork cambium,
and secondary cortex)
BARK
vascular cambium
secondary
phloem
HEARTWOOD
SAPWOOD
Annual Rings
• Concentric rings of secondary xylem
• Alternating bands of early and late wood
• Early wood
– Xylem cells with large diameter, thin walls
• Late wood
– Xylem cells with smaller diameter, thicker
walls
Types of Wood
• Hardwood (oak, hickory)
– Dicot wood
– Xylem composed of vessels, tracheids,
and fibers
• Softwood (pine, redwood)
– Gymnosperm wood
– Xylem composed mostly of tracheids
– Grows more quickly
• Plant Nutrition: Nitrogen and Iron
Deficiencies
Resources
• http://www.botany.uwc.ac.za/ecotree/cel
ltissues/tissues.htm#top
• Plants in Motion:
http://plantsinmotion.bio.indiana.edu/pla
ntmotion/starthere.html