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Course II (Chapter 8: Structure of Woody Plants (Secondary Xylem (Growth…
Course II
Chapter 8: Structure of Woody Plants
Secondary Xylem
Reaction Wood
Contains many special Gelatinous Fibers
Exert tension on the branch
aka Tension Wood
Mostly on upper side of Branch
Caused by stress
Heartwood and Sapwood
Tylosis
Plug separating Heartwood & Sapwood
Sapwood
New layer formed each year
More Moist
Light, Outer Wood
Heartwood
One Growth ring is converted to Heartwood each year
More Fragrant
Drier
Dark, Center Wood
Growth Rings
Ring Porous
Examples:
Honey Locust
Sassafras
Red Oak
Vessels restricted to Early Wood
Diffuse Porous
Examples:
American Holly
Sugar Maple
Aspen
Yellow Birch
Wood of Growth Ring has Vessels throughout
Annual Ring
aka Growth Ring
Made of:
Late Wood
Early Wood
Late Wood
Needs more mechanical strength
Lower proportion of Vessels
aka Summer Wood
Early Wood
High proportion of Wide Vessels
aka Spring Wood
First Wood Formed
Vascular Cambium is Quiescent during Stress
Types of Wood Cells
Secondary Xylem
May contain:
Parenchyma
Sclereids
Fibers
Vessel Elements
Tracheids
Contains all cells that occur in Primary Xylem
Difference in the arrangement of cells
Radial System
Can contain Ray Tracheids
Horizontal, Rectangular Cells
Contains only parenchyma
Two Types:
2 more items...
Stores Carbohydrates
In masses called Rays
In woody angiosperms
Develops from Ray Initials
Axial System
Contains few or no fibers
Softwoods
1 more item...
Contain fibers to give wood strength
Hardwood
2 more items...
Always contains Tracheary Elements
Carries out Longitudinal conduction of water
Develops from Fusiform Initials
Formed to the interior of Vascular Cambium
Outer Bark
Cork and the Cork Cambium
Cork Cambium
aka Phellogen
Results from activation of Parenchyma cells in Secondary Phloem
Differs from Vascular Cambium
Structurally
Morphogenically
Cork Cell
aka Phellem Cell
May produce a few new cells
Phelloderm
Periderm
Cork Cambium
Layers of Cork Cell
Phelloderm
Offers temporary Protection
Outer Bark
Outside innermost cork cambium
Inner Bark
Between Vascular Cambium and Innermost Cork Cambium
Lenticels and Oxygen Diffusion
Cork blocks oxygen absorption
Bark becomes Permeable to Oxygen
Lenticels
Aerenchymatous Cork
Pathway for Oxygen
Initiation of Cork Cambia
Epidermises >40 years old have been reported
Timing is variable
Later Cork Cambium form deep in the secondary Phloem
Vascular Cambium
Arrangement of Cambial Cells
Fusiform Initials
Nonstoried Cambium
Irregular Rows
Storied Cambium
Occurs in
Persimmon
Redbud
Evolved more recently
Regular horizontal rows
Ray Initials
Uniseriate, Biseriate, or Multiseriate
In short vertical rows
Grouped together
Organized in Specific Patterns
Fusiform Initials
Occasionally divide by Anticinal Walls
Increases number of Cambial Cells
Orientation is constant
Longitudinal cell division produces 2 elongate cells
Cell of Secondary Xylem or Secondary Phloem
One is Fusiform Initial
Long, tapered cells
Ray Initials
Produce mostly Storage Parenchyma
Undergo Periclinial Cell Division
One Daughter becomes Xylem Parenchyma or Phloem Parenchyma
One daughter remains Cambial Ray
Short, Cubodial
Similar to Fusiform Cells
Initiation of the Vascular Cambium
Vascular Cambium
Has 2 types of cells:
Ray Initials
Fusiform Initials
Shares many features with Apical Meristem
Rarely forms leaves that can stay for years
Must be extended each year
Older Interfascicular/Fascicular Cambium
Interfascicular Cambium
Connects on each side to Fascicular Cambia
Vascular Cambium becomes Cylinder
Mature Parenchyma cells come out of Cell Cycle arrest
Resume Mitosis
Fascicular Cambium
Cells between Metaxylem & Metaphloem never undergo Cell Cycle Arrest
Cells continue to divide instead of Maturing
Fasicle=Bundle
Meristem producing secondary plant body
Secondary Phloem
Radial System
Axial System
Contains companion cells or Sieve cells
Contains sieve tube members
Responsible for conduction
Secondary Growth in Roots
New Vascular Cambium
Arises like Interfascicular Cambium
Same star shape as Primary Xylem
Becomes circular
Ray & Fusiform Initials
Perennial Roots form Bark
Anomalous Forms of Growth
Unusual Primary Growth
Palms
All Primary Tissue
Vascular Bundles distributed throughout Ground Tissue
Establishment growth
Increase in Width
Addition of Adventitious Roots
Anomalous Secondary Growth
Roots of Sweet Potatoes
Storage Parenchyma is increased
Xylem & Phloem are purely Parenchyma
Secondary Tissues (Irregular)
Parenchyma
Sieve Tubes
Vessels
Vascular Cambia
Included Phloem
Cambium produces ordinarily
Cambium cells differentiate into Xylem
Secondary Phloem cells form new Cambium
Included Phloem
Unequal Activity of the Vascular Cambium
2 sectors inactive
2 sectors active
Bauhinia
Plant remains flexible
Secondary Growth in Monocots
Joshua Trees
Anomalous Secondary Growth
Dragon Trees
Anomalous Secondary Growth
Palms
Chapter 12: Transport Processes
Long Distance Transport: Xylem
Control of Water Transport by Guard Cells
Powered primarily by water loss to the atmosphere
Numerous mechanisms control stomatal opening and closing
Water Transport Through Xylem
Cohesion-Tension Hypothesis
Most widely accepted model
Stomatal pores open, allow water loss
Water molecules diffuse into atmosphere
Transstomatal Transpiration
Warm air= —50MPa
Much water loss
Transcuticular Transpiration
Water loss directly through the cuticle
Cavitation
Breaking of Hydrogen Bonds over a large region
Causes breaking of water columns
That tracheid or vessel can never conduct water again
All eventually Cavitate
Embolism
aka Air Bubble
Properties of Water
Cohesive
Adhesive
Adheres firmly to soil particles
Heavy
Diffusion, Osmosis, and Active Transport
Diffusion
Random particle movement causes them to move to lower concentrated areas.
Osmosis
Diffusion through a membrane
Types of Membranes:
Freely Permeable
Allows diffusion of ALL solutes
Completely Impermeable
Allows diffusion of NO solutes
Selectively Permeable
Allows diffuion of SOME solutes
Water molecules pass through all membranes
Membranes have:
Aquaporins (some)
Causes water to pass through rapidly
Molecular Pumps
Use ATP to force molecules across membranes
aka Active Transport
Binds to molecule & ATP
Water Potential
Cells and Water Movement
Incipient Plasmolysis
Plasmolyzed
Protoplast continues to pull away from wall
Protoplast loses water and pulls away from the wall
Lysis
Animal cells burst if placed in pure water
Movement of Water
Water potentials must always be considered in groups
If 2 regions have the same water potential, they are in equalibrium
Occurs when there is a difference in water potential within the mass of water
Chemical potential of water
Can be increased by:
Water being heated
Water being put uner pressure
Water being elevated
Can be deacreased by:
Water being cooled
Reducing pressure on water
Lowering Water
Matric Potential
Always negative
Adhesion decreases Water’s free energy
Water’s adhesion to nondissolved structures
Osmotic Potential
Related to # of particles present in solution
Adding solutes decreases water’s free energy
0.0MPa in Pure Water
Pressure Potential
Positive Pressure
Compression
Negative Pressure
Stretched
Measured in Megapascals
Short-Distance Intercellular Transport
Apoplast
Wall and Intercellular Spaces
Symplast
One continuous mass of Protoplasm
Guard Cells
Thrown out of Hydraulic Equilibrium by Potassium Pumping
At night
In Hydraulic Equilibrium with surrounding cells
Little internal pressure
Shrunken
Motor Cells
Located along the Midrib
Can accumulate or expel Potassium
Adjusts water potential
Cells at the point of flexure
Transfer Cells
Found where rapid short-distance transport occurs
Regions where sugar is loaded into/out of Phloem
Areas that pass nutrients to embryos
Glands that secrete salt
Outer walls are smooth
Has many finger-like outgrowths on Inner Surface
Long Distance Transport: Phloem
Pressure Flow Hypothesis
Exact mechanism is not known
Sources
Site from which water & nutrients are transported
Spring & Summer=leaves
Germinating Embryos=Cotyledons/Endosperm
Polymer Trap Mechanism
Conducting-cell Plasma Membranes
Permeable to Monosaccharides
Permeable to Disaccharides
Impermeable to Polysaccharides
STM/CC complex
Functional unit consisting of:
Conducting Cell
= or > 1 Companion Cell
Mass Transfer
Sugars & Nutrients transported by Phloem per hour
Specific Mass Transfer
Divided into Cross-Sectional area of Phloem
Sinks
Sites receiving transported Phloem Sap
Frequently break sieve elements
2 mechanisms seal:
P-protein
Fine network adjacent to the plasma membrane inner surface of uninjured sieve elements
P-protein Plug
Formed when P-protein is too large
Callose
Stays in solution only under pressure
Precipates into Flocculent Mass
Extremely Diverse
Not all simultaneously active
Sugars are actively unloaded from sieve elements
Chapter 3: Cell Structure
Plant Cells
Cell Wall
Secondary Cell Wall
Primary Cell Wall
Microfibrils
Bound by Hemicelluloses
Contains Polysaccharide Cellulose
Storage Products
Microfilaments
Actin
Assembly of Globular Proteins
Microtubules
Makes up Centriole
Tubulin
Beta-Tubulin
Alpha-Tubulin
Means of Motility
Flagella
Cilia
Acts as Cytoskeleton
Easiest Studied
Most Abundant
Cytosol
Free Ribosomes
Productsof Enzymatic Reactions
Intermediates
Chemical Precursor
Enzymes
Water
Microbodies
Glyoxysomes
Converts stored fat to sugar
Only in Plants
Peroxisomes
Detoxification
Dictyosomes
Golgi body
Cisterna
Maturing Face
Vesicles Released
Forming Face
Vesicles Accumulate
Endoplasmic Reticulum
Missing Ribosomes
Smooth ER
Carries Large Particles
Ribosomes attach to it
Rough ER
Ribosomes
Forms Polysome
Protein Synthesis
Immersed in Protoplasm
Plastids
Proplastids
Amyloplasts
Accumulate Sugar
Chloroplasts
In young cells
Synthesis, Storage, Export
Outer Membrane
Inner Membrane
Thlyakoids
Granum
Photosynthesis
Mitochondria
Inner Mitochondrial Membrane
Forms Cristae
Selectively Permeable
Outer Mitochondrial Membrane
Freely Permeable
Gives Shape
Cristae
Folded Membranes
Respiration
Energy in Adenine Triphosphate (ATP)
Cytoplasm
Central Vacuole
Not in Animal Cells
Digestive Organelle
Tonoplast
Mostly Impermeable
Expand and Merge as Cell Grows
aka Vacuole Membrane
Nucleus
Nucleolus
Ribosomes are synthesized, and assembled
Nucleoplasm
Water
RNA
Histone Proteins
Enzymes, etc. to read DNA
DNA
Surrounded by Nuclear Envelope
Inner Membrane
Outer Membrane
Permanent Storage
Plasma Membrane
Selectively Permeable
Covers the Protoplasm Surface
aka Plasmalemma
Protoplasm
Makes up the Cell
Mass of:
Water
Nucleic Acid
Lipids
Proteins
Association of Cells
Intercellular Spaces
Apoplast
Plasmodesmata
Symplast
Primary Pit Field
Connect Plant Cells
Fungal Cells
Walls contain Chitin
Similar to Cellulose
Do not contain Plastids
Basic Cell Types
Prokaryotic
Bacteria
Eukaryotic
Plants
Animals
Fungi
Protists
Membranes
Composition of Membranes
Proteins
In Bilayer=Intrinsic Proteins
Domains
Fluid Mosaic Membrane
Ogliosaccharides
Glycoprotein
Outside Membrane=Extrinsic Proteins
Two layers of phospholipid molecules
Calm Water=Monolayer
Agitated Water=Bilayer
Very thin
Properties of Membranes
Capable of Growth
Permits movement of Membrane Pieces
Vesicles
Exocytosis
Excretes almost anything
Endocytosis
Opposite of Exocytosis
Small opening
Permeability
Selectively Permeable Membrane
Freely Permeable Membrane
Impermeable Membrane
Movement of Charged Substances
Facilitated Diffusion
Active Transport
Compartmentalization
Chapter 4: Growth and Division of the Cell
Less Common Types of Division in Plants
Cell division without Nuclear Division
Common in:
Nutritive tissues of seeds
Fungi
Algae
Karyokinesis
Coenocyte
100s of Nuclei in one cell
Formation of Multinucleate cells
Growth Phase of the Cell Cycle
aka Resting Phase
S Phase
Gene Amplification
Arum maculatum
24, 576 copies of every gene
Only some genes are repeatedly replicated
Endoreduplication
Occurs most often in cells with rapid metabolism
Occurs in 80% of Maturing Plant Cells
Histones complexes with DNA
Provides: Protection and Structure
Genes in the Nucleus are replicated
Entire Chromosomes replicated
G2 Phase
Division occurs immediately after
Produces proteins
Lasts 3-5 hours
Cells prepare for division
G1 Phase
Some cells are here for life
Longest Part of Cell Cycle
Synthesis of Nucleotides
Division Phase of the Cell Cycle
Meiosis
Meiosis II
Telophase II
New Nuclei are formed
Anaphase II
Seperates new chromosomes from replicate
Metaphase II
Centromeres divide
Very short
Prohase II
Prepares nucleus for division
Not divided into stages
Opposite of Telophase I
Meiosis I
Telophase I
Chromosomes uncoil
Interkinesis
Opposite of Prohase II
Anaphase I
Each chromosome has 2 chromatids
Chromosomes seperate, moving to opposite ends of the Spindle
Metaphase I
Metaphase Plate is formed
Prophase I
Diakinesis
Chromosomes continue to seperate
Diplotene
Attached at Chiasmata
Chromosomes move away from each other
Pachytene
Crossing-over
Chromosomes become shorter and thicker
Zygotene
Synapsis
Each chromosome pairs with its homolog
Bivalent
Pairing of Chromosomes
Leptotene
Chromosomes begin to condense
aka Reduction Division
Zygote is formed
Cytokinesis
Phragmosome
Vacuole Division
Formation of Phragmoplast
Cell Plate
Forms in cell center
Preprophase Band
Identifies plane of division
Division of Protoplast
Mitosis
Telophase
Reversal of Prophase
Produce ribosome subunits
Chromosomes become less distinct
Form complete nuclear envelopes
Anaphase
Uses 20 ATP Molecules
Spindle Microtubules pull each chromosome away
Metaphase
Chromatids are freed
Chromosomes move to the Metaphase Plate
Prophase
Spindle Microtubules attach to Centromeres
Chromosomes Condense & Coil
Duplication Division
Nuclear genes are first copied
Cell Division in Algae
Cytokinesis
Phycoplast
Microtubules perpendicular to spindle
Similar to animal cell cytokinesis
Nuclei
Dinflagellate nucleus
Has no histones
Gaps form in nuclear envelope
Has both intrnuclear abd extranuclear spindle
Plant nucleus identical to animal nucleus
Cell Division of Prokaryotes
Very short process
Cytokinesis occurs by infurrowing
DNA pulled as cell grows
No histones
No Mitosis/ Meiosis
Chapter 7: Roots
Other Types of Roots and Root Modifications
Roots of Strangler Figs
Strangler roots kill host tree
Roots fuse to each other when they meet
Roots encircle host tree’s trunk
Haustorial Roots of Parasitic Flowering Plants
Tristerix
Typically adhere firmly to it’s host
Very little root-like structure remains
Highly modified Roots of Parasitic Plants
Root Nodules and Nitrogen Fixation
Rhizobium
Nitrogen-fixing bacteria
Infection thread
Bacteria releases into plant cell cytoplasm
Proliferates rapidly
Root Nodule
May become Complex
May remain simple
Nitrogen Fixation
Chemical conversion of atmospheric nitrogen into usable compounds
Mycorrhizae
Types of Relationships:
Endomycorrhizal
In Herbaceous Plants
Hyphae penetrate root cortex to the endodermis
Ectomycorhizal
In woody forest plants
Fungal Hyphae penetrate between root cortex cells
Roots of Seed Plants
Have a Sybiotic Relationship with Soil Fungi
Contractile Roots
Fairly common
Caused by changes in the shape of the Cortex Cells
Vascular Tissues buckle
Shorten and Expand rapidly
Found in:
Crinum
Gladiolus
Oxalis
Aerial Roots of Orchids
Root Epidermis
Waterproof
Composed of Large, Dead Cells
aka Velamen
Epiphytic
Roots dangle freely
Attached to Branches of Trees
Prop Roots
Buttress Roots
Brace the Trunk
Upperside grows more Rapidly
Exposed roots
Ficus
Prop roots spread to produce Massive Trees
Pandanus
Stem of a Monocot can:
IF it can produce Adventitious Roots extending to the soil
Have more Vascular Bundles
Become wider
Storage Roots
Only Permanent Organs
Perennial Species
Phlox
Datura
Biennial Species
Carrots
Beets
Celery
Long-term storage for Carbohydrates
Used to Produce a New Shoot
Accumulate during Summer Photosynthesis
Origin & Development of Lateral Roots
Initiated by cell division in the Pericycle
Some cells become densely Cytoplasmic
Resumes mitotic activity
Creates Small Root Primordium
Organizes into Root Apical Meristem
Destroys cells of Cortex & Epidermis
Breaks Endodermis
Initiated deep in the Root
Endogenous Origin
Never develop into Flowers
External Structure of Roots
Organization of Root Systems
Fibrous Root System
Radicle dies during/after germination
Root Primordia form first stages of Fibrous System
Adventitious Roots
Increase Transport Capacities
Increase Absorption
Highly Branched Root System
Branch Roots
Lateral Roots
Can become Prominently Swollen similar to Taproots
Cassava
Sweet Potatoes
May produce more Lateral Roots
Single Prominent Taproot
Examples:
Turnips
Beets
Carrots
Largest Root in the System
Develops from Radicle
Must have an Enormous Absorptive Surface
Structure of Individual Roots
Root Hair Zone
Root Hairs
Die after 4-5 days
Extremely transitory
Unicellular
Form in nonelongated part of the Root
Greatly increase Root’s Surface Area
Epidermal cells extend as Narrow Trichomes
Behind Zone of Elongation
Zone of Elongation
Cells undergo Division & Expansion
Behind Root Cap
Apical Meristems
Shoot Apical Meristem
Protected by bud scales or young foliage leaves
Root Apical Meristem
Protected by Root Cap
Dictyosomes secrete Mucigel
Embedded in Solid Matrix
Not all parts extend at once
Discrete Apical Meristem
Only feasible longitudinal growth
Root Tip
Growth in Length occurs
No Axillary Buds
No Leaf Axils
Internal Structure of Roots
Root Cap
Sloughs off in 4-5 days
Consistantly regenerating
Cells are small, & meristematic at first
Cells detect Gravity
Starch grains settle at lower side of cell
Root Apical Meristem
Quiescent Center
More resistant to harmful Chemicals
Reserve of Healthy Cells
More orderly than Shoot
Zone of Elongation
Cells enlarge
Similar to Shoot’s Subapical Meristem
Cells differentiate into a Visible Pattern
Protoderm
Outermost cells
Differentiate into Epidermis
Provascular Tissue
In the Center
Develop into primary Xylem & primary Phloem
Larger cells develop into Metaxylem & Metaphloem
Tissues are permeable
Zone of Maturation
aka Root Hair Zone
Root Hairs grow outward
Greatly increases absorption of water/minerals
Merges gradually with Zone of Elongation
Cotex Cells
Continue to enlarge
Transfer of Minerals from Epidermis to Vascular Tissue
By Apoplastic Transport
By Absorption
Minerals do not have free access to Vascular Tissue
Endodermis
Tangential Walls
Closest to Cotex
Radial Walls
The Top, Bottom, Side Walls
Encrusted with Lignin & Suberin
Waterproof
Casparian Strips
Controlling types of Minerals that enter the Xylem Water Stream
Impermeable
Excludes Harmful Minerals
Pericycle
Parenchyma cells constitute an irregular region
Initiates lateral roots
Mature Portions of the Root
Passage Cells
Only have Casparian Strips
Once thought to represent passageways for mineral absorption
Suspected to be merely slow to develop
Root Pressure
Caused by Absorption of Minerals & Water in the Root Hair Zone
Endodermis Maturation produces Watertight Sheath around Vascular Tissues
Chapter 6: Leaves
External Structure of Foliage Leaves
Veins
Parrallel Venation
Occurs in Monocots
Reticulate Venation
Occurs in Eudicots
Occurs in Angiosperms
Collect sugars
Distribute water from stem to leaf
Bundles of Vascular Tissue
Petiole
Abscission Zone
Cuts off leaf when life is over
:forbidden:No Petiole = Sessile Leaf
Aeonium
Holds Blade into light
aka Stalk
Leaf Blade
Compound Leaf
Blade Divided into several parts
Attached to Rachis
aka Leaflets
Simple Leaf
One-Part Blade
Ventral Surface
Adaxial
Usually smooth
Upper side of Blade
Dorsal Surface
Abaxial
Large Protruding Veins
Lower side of Blade
Flat, Harvesting Portion
aka Lamina
Functions
Must not be delicious to animals
Must not allow entry of Fungi, Bacteria, or Epifoliar Algae
Must not lose water
Photosynthesis
Converts Carbon Dioxide to Carbohydrate
Internal Structure of Foliage Leaves
Epidermis
Transpiration
Water is lost
Roots must be able to replace lost water
Consists of:
Flat, Tabular Ordinary Epidermal Cells
Guard Cells
Trichomes
Glandular
Non-Glandular
Functions:
Provide Shade on Upper Surface
Prevent Rapid Air movement on Lower Surface
Makes walking/chewing difficult for insects
Remarkably Hairy
Leaf Stomata are frequently sunken into Epidermal Cavities
Mesophyll
Ground tissue interior to the Epidermis
Palisade Parenchyma
aka Palisade Mesophyll
Main photosynthetic tissue
Exposed to intercellular spaces
Spongy Mesophyll
Open, Loose Aerenchyma
Permits Carbon Dioxide to diffuse rapidly
Vascular Tissues
Between Palisade Parenchyma and Spongy Mesophyll
Midrib
aka Midvein
Lateral Veins
Minor Veins
Release water from Xylem
Loading sugar into Phloem
Conduction
Conduction
Bundle Sheath
Bundle Sheath Extension
Petiole
Massive in:
Palms
Rhubarb
Celery
Water Lillies
Transition between stem and Lamina
Leaf Traces
Vascular bundles
Stipules
Protect Apical Meristem
Die early in Mature Leaves
Morphology and Anatomy of Other Leaf Types
Succulent Leaves
Lack Air Space in Mesophyll
Favors water conservation
Thick and Fleshy
Characteristics of:
Aizoaceae
Ice plant
Portulacaceae
Lewisia
Portulaca
Crassulaceae
Sedum
Kalanchoe
Permits survival in desert habitats
Sclerophyllous Foliage Leaves
Resistant to animals, extreme temerpatures, and ultraviolet light
Perennial Leaves
Yucca
Agave
Holly
Barberry
Soft, Flexible, Edible
Must produce more sugar by photosynthesis than is used
Limited Sclerenchyma
Leaves of Conifers
Sclerophylls
Epidermis & Hypodermis cells with thick walls
Thick cuticle
Contains unpalatable chemicals
Never compound
Needles
Pines
Firs
Spruces
Small Scale-like leaves
Junipers
Cupressus
Thuja
Large, Broad Scales
Agathis
Araucaria
Podocarpus
Mostly perennial
Deciduous
Larix
Taxodium
Metasequoia
Bud Scales
Tough and waxy
Small, or nonexistent Petiole
Small, Mostly Simple
Protect Apical Meristem from cold temperature and wind
Most common modification of leaves
Spines
Cacti
Spines = Axillary Buds
No Mesophyll Vascular Bundles
No Mesophyll Parenchyma
Microscopic Green Leaves
Tendrils
Cells can sense contact
Grows indefinitely
Examples:
Squash
Cucumber
Peas
Leaves with Kranz Anatomy
Plants with C4 photosynthesis
Lack Palisade Parenchyma & Spongy Mesophyll
Prominent Bundle Sheaths
Insect Traps
Leaves are:
Capable of Photosynthesis
Parenchymatous
Thin
Examples:
Sarracenia
Darlingtonia
Nepenthes
Habitats are poor in nitrates and ammonia
Obtain nitrogen by digesting insects
Initiation and Development of Leaves
Basal Angiosperms and Eudicots
Leaves produced Apical Meristem
Leaf Primordium
Consists of:
Leaf Ground Meristem
Leaf Protoderm
Protrusion at base of Meristem
Monocots
Protoxylem & Protophloem are constantly stretched
Leaf Primordium
Cylinder Shaped
Apical Meristem cells become part of the primordium
Chapter 5: Tissues
Basic Types of Cells snd Tissues
Sclerenchyma
Mechanical Sclerenchyma
Short Sclereids
Often dead at maturity
Elastic Secondary Walls
Long Fibers
Involved in storage
Found where strength, fexibility are important
Elastic Secondary Walls
Conducting Sclerenchyma
Vessel Elements
Exculsively in Flowering Plants
Dead at Maturity
Few Preforations
Short and Wide
Tracheids
Found in Vescular Plants
Dead at Maturity
Contain no Preforations
Long and Narrow
Unusable for Shoot Tips
Deforming Forces:
Snow
Animals
Wind
Develop from Parenchyma Cells
Primary Wall
With a Thick Secondary Wall
Mostly lignified
Collenchyma
Powerfully Absorbs Water
Similar to air pressure in a tire
Present in elongating Shoot Tips
Must be long and flexible
Primary Walls
Exhibits Plasticity
Remain thin in some places, thick in others
Requires more glucose for production
Parenchyma
Powerfully Absorbs Water
Some die at maturity
Open to release seeds/pollen
Subtypes:
Transfer Cells
Mediate short-distance transport of material
Glandular Cells
Secretes:
Oils
Resins
Mucilage
Fragrances
Nectar
Chlorenchyma Cells
Numerous Chloroplasts
Involved in Photosynthesis
Parenchyma Tissue
Phloem
Conducts nutrients over long distances
Mass of Parenchyma Cells
Primary Walls
Remain thin
External Organization of Stems
Bulbs
Examples
Garlic
Daffodils
Onions
Thick leaves
Rhizomes
Tubers
Short growth period
Fleshy horizontal stems
Corms are Vertical
Short Shoots
Phyllotaxy
Spiral Phylotaxy
Each leaf is located slightly to the side.
Decussate Phylotaxy
Leaves are arranged into 4 rows
Distichous Phylotaxy
Leaves are arranged into 2 rows
Irises
Corn
Whorled Phylotaxy
3+ leaves per node
Opposite Phyllotaxy
2 leaves per node
Alternate Phyllotaxy
One leaf on each node
Arrangement of leaves on the stem
Leaf Axil
Axillary Bud
Covered in Bud Scales
Terminal Bud
Extreme tip of each Stem
Modified Leaves
Mini shoot with several young leaves
Stem area above leaf attachment
Internodes
Narrow
Ex: Alfalfa Sprouts
Intermediate
Wide
Ex: Asparagus
Regions between Nodes
Nodes
Where leaves are attached
Internal Organization of Stems
Vascular Bundles
Collateral
Primary Phloem
Primary Xylem
Phloem
Sieve Element
Sieve Pores
Group = Sieve Areas
Enlarged Plasmodesmata
Sieve Tube Members
Sieve Areas on Side Walls
Short and Wide
Sieve Cells
Evolved First
Has Sieve Areas Everywhere
Long and Narrow
Xylem
Tracheary Elements
Annular Second Wall
Reticulate Thickening
Net-Shaped
Scalariform Thickening
Underlies primary wall and is extensive
Helical Thickening
Helices interior to Primary Wall
Annular Thickenings
Weak
Set of Rings
Vessel Elements
Stack = Vessel
Absorb Water
Few Perforations
Ends Flat
Short and Wide
Tracheids
No Perforations
Ends Pointed
Long and Narrow
Vascular Tissues
Not Circulatory
Phloem
Distributes Sugars and Minerals
Xylem
Conducts Water and Minerals
Unicellular or thin sheets of cells
Cortex
Fit together compactly
Composed of Tosynthetic Parenchyma
Interior to Epidermis
Epidermis
Can elongate into Trichomes
Makes it hard for animals to hurt leaves
Gaurd Cells
Hole called Stomatal Pore
Make up Stoma
Encrusted in Cutin
Inhibits entry of Carbon Dioxide
Cuticle
Impermeable to Water
Fatty substance
Functions
Barrier against Bacteria, etc
Prevents Loss of Water
Prevents Overheating
Single layer of Parenchyma Cells
Outermost surface of Herbaceous Stem
Stem Growth and Differentiation
Subapical Meristem
Metaxylem
Metaphloem
Large Sieve Areas
Protophloem
Largest Tracheary Element
Protoxylem
Also produces new Cells
Apical Meristems
New Cells are Created
