Unit 2: Plant Structure &
Anatomy
Chapters 3 & 4
Unit 2: Plant Structure & Anatomy
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Unit 2 Objectives:
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Understand & Identify vegetative and reproductive
parts of the plant
Knowledge of various types of roots, stems,
leaves, flowers, and fruit
Comprehension of cell structure and function
Be able to illustrate the function of xylem, phloem,
cell division, etc.
Unit 2: Plant Structure & Anatomy
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Plan of the Entire Plant
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Focus on the Angiosperm (seed enclosed in a
fruit)
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Monocot – one seed leaf
Dicot – two seed leaves
Roots
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Anchor
Absorb water & nutrients – transport to the stem
Store food produced by the aboveground part of the
plant
Unit 2: Plant Structure & Anatomy
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Major parts of the root system:
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Primary root
 Arises from the embryo
 A.k.a the tap root
 Usually very short-lived and is replaced by the
secondary root
Secondary root or rootlets
 Branches (often fibrous) from the tap root
 Often become the permanent root system
Root hairs
 Small enough to penetrate openings in the soil structure
 Major role in nutrient absorption
Unit 2: Plant Structure & Anatomy
Large #’s near the tips of the roots
 Damage during transplant often causes wilting, due to
the loss of water-absorption capacity
Taproots
 All other rootlets originate from here
 Can divide, become fleshy, penetrate deep into the soil
 Can you identify some plants w/ taproots?
Fibrous roots
 No distinguishable primary root
 Many fine roots of similar size originating from the stem
 Often spread near the soil surface
 What are some plants w/ fibrous root systems?
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Unit 2: Plant Structure & Anatomy
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Fleshy or Tuberous roots
 Food reservoirs for surpluses
 Food may be used when growth resumes
 Can you name some of these plants?
Aerial roots
 Can form on land and water plants in a favorable, moist
environment
 Usually for climbing plants
 Mostly attach to a host, but can absorb water from the
air
Knees
 Used by bald cypress trees in swampy areas to reach
air
 Protrude above the surface of the water
Unit 2: Plant Structure & Anatomy
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Stems
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Helps form the major aboveground structure of the plant
Attachment point for leaves, flowers, and fruit
Contains the vascular system
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Distribute food and water
Xylem
 System by which water & nutrients are transported and
distributed up through the plant
Phloem
 Food and materials generated from photosynthesis
transported and distributed throughout the plant
Unit 2: Plant Structure & Anatomy
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Develops from a bud to bear leaves and more buds
Swelled points called nodes
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Arrangements of vessels differ in monocots and dicots
 Scattered bundles in the stem of monocots
 Circular zones separated by a cambium layer in dicots
(cambium layer produces new sets of xylem/phloem
cells)
Point on a stem where leaf is/was attached
Area between nodes called the internode
Can be adapted for food storage, or be specialized
(runners, thorns, etc.)
Unit 2: Plant Structure & Anatomy
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Types of stems:
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Crowns
 Short, almost unnoticeable stems
 Also known at the base of the stem where roots begin
Simple
 Stems w/out branches
 What is an example?
Branched
 Stems w/ more than one terminal bud, sidegrowth, or
branch
Unit 2: Plant Structure & Anatomy
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Climbing
 Too weak to support itself
 Lean, or twist on something else for support
 Examples?
Creeping
 Rest on the surface of the ground
 Send down roots at nodes or joints
Rhizomes
 Subterranean stems
 Leaves on one side and roots on the other
Stolons
 Slim stems along the ground that root at the nodules
(strawberry)
Unit 2: Plant Structure & Anatomy
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Leaves
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Main function is to make food and other chemicals
(proteins, fats, oils) used for growth/reproduction
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Any part of the green plant can also do this
Parts of the leaf
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Blade
Petiole
 “stem” of the leaf
 Optional part – leaf may be directly attached to the stem
(known as sessile)
Stipule
 Small leaflike appendages at the base of the petiole
 Not all plants have them
Unit 2: Plant Structure & Anatomy
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Grass leaves
 Sheath – base of the leaf blade that surrounds the stem
 Can have a collar like extension at top of the sheath
called a ligule
 Auricles – surround the stem at the junction of the
sheath and blade (some grasses)
Simple vs. Compound Leaves
 Simple = leaf consisting of one blade (grass, oak, apple)
 Compound = several leaflets, may be joined on one
petiole, or along the central axis of the leaf
Unit 2: Plant Structure & Anatomy
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Leaf Shape
 Shape, margin, tip, and base are all defining
characteristics of the species
Vein Arrangement in the Leaf (Venation)
 Parallel (grasses)
 Dichotomous or forked (ferns)
 Pinnate – veins extend from a midrib vein
 Palmate – veins extend from the petiole
Leaf Arrangement on the Stem
 Usually very definite arrangement
 Protrude from the nodules
 Alternate, opposite, whorled, etc.
Unit 2: Plant Structure & Anatomy
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Flowers
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Reproductive part of angiosperms
Complete flowers contain both male and female organs
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Male
 Stamen
 Produces pollen
Female
 Pistil
 Receives pollen and forms seeds
What are some examples?
Unit 2: Plant Structure & Anatomy
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Separate flowers
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Male and female parts both on same plant, but in different
locations
 What is an example?
Other flowers
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Single
 One, single flower at the end of an elongate stalk
 Stalk bearing the flower called the peduncle
Cluster
 3 or more flowers gathered close together
 May be simple or branched groups
 Pedicel – individual stalk of a flower in a cluster
Unit 2: Plant Structure & Anatomy
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Inflorescense
 Arrangements of flowers or groups of flowers on a plant
 Diversity in the arrangement
Flower Positions
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Terminal
 Flowers or clusters are on end of axis or branch
Axillary
 Flowers or clusters at the junction of the stem and the
leaf
May have both flower positions
Unit 2: Plant Structure & Anatomy
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Flower Parts
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Flower is a highly differentiated & specialized branch of the
stem w/ modified leaves or flower parts
Site of sexual reproduction
Most distinctive structure
Guide for separating flowering plants into major groups
Accessory Organs
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Perianth
 Outer floral parts
 Composed of the calyx & corolla
Calyx
 Ring of sepals making up the outermost part
 Leaflike
 Usually green, but can be any color
 Protection for the other floral parts
Unit 2: Plant Structure & Anatomy
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Corolla
 Inner set of leaflike parts inside the calyx
 Composed of petals
 Usually white or bright colored to attract insects to the
nectar
 Protect the inner organs of the flower
Receptacle/Torus
 Apex of the pedicel where the organs of the flower are
developed
Floral Bracts
 Modified leaves that simulate petals
 Make inconspicuous flowers more obvious
Unit 2: Plant Structure & Anatomy
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Essential Organs
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Reproductive structures responsible for the survival of the
species
Stamens
 Male reproductive organs
 May be attached to the receptacle or the corolla
 Filament – thin stalk attaching the anther to the flower
 Anther – lobed, oblong, baglike on top of the filament;
produces pollen that develops the male germ cells;
usually yellow, 1-4 cavities where pollen is released
 Pollen – tiny specks; may form a layer of powder;
usually one-celled; spherical, ovoid, or disklike; ridges,
spines, and germ spores on outside, very different from
specie to specie; used in ID
Unit 2: Plant Structure & Anatomy
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Stamens may be opposite or alternate w/ the petals
Pistils
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Female reproductive organ
Usually in the center of the flower
Surrounded by stamens, petals, sepals
May have single or multiple pistils, depending on the specie
 Carpel – either a simple pistil, or one segment of a
compound pistil
Flask or bottle-shaped
Style
 Elongated stalk connects ovary w/ stigma
Unit 2: Plant Structure & Anatomy
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Ovary
 Enlarged, bulbous, base part of the pistil
 Holds the ovules attached via placenta
 Attached to the inner wall or the central axis
 One egg/ovule, 2+ ovules/carpel
 Normally develops into the fruit containing the seeds
Stigma
 Tip of the style/pistil specialized to receive pollen grains
 May be divided into may slender parts
Compound pistils have many, united carpels
 May be so complete that it includes the entire female
parts of the flower
Unit 2: Plant Structure & Anatomy
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Flower Classification
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By presence/absence of parts
Complete Flowers
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Incomplete Flowers
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Calyx, corolla, stamen, pistil
Four “regular” parts
Lack one or more of the previous four
Perfect Flowers
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Both stamen & pistil
May lack sepals or petals
Unit 2: Plant Structure & Anatomy
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Imperfect Flowers
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Naked Flowers
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No petals
Staminate Flowers
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No petals or sepals
Apetalous Flowers
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Lack either stamen or pistil
May/may not have sepals or petals
Have stamen(s)
No pistils
Pistillate Flowers
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Have pistil(s)
No stamen
Unit 2: Plant Structure & Anatomy
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Terms used to describe flowering characteristics
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Monoecious
 Both staminate and pistillate flowers on the same plant
 Examples? Oak, Corn
Dioecious
 Staminate and pistillate flowers on separate plants
 Examples? Holly, Brazilian pepper
Polygamous
 Staminate, pistillate, and hermaphroditic flowers on the
same plant
 Example? Red Maple
Unit 2: Plant Structure & Anatomy
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Flower Forms
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More specific way to identify flowering plants
Things to consider with identification of flower forms
 Degree to which floral parts connect
 Placement of floral parts on the receptacle
 Variance in the number of subdivisions of the four
regular parts of the flower
 Variance in the symmetry of the flower forms
Fruit
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Protection for seed
Means of dispersal
Ripened, seed-bearing ovaries of flowers
Unit 2: Plant Structure & Anatomy
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Dry fruits
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Usually dull in color
Thin, dry wall of the ovary
Can be further subdivided
 Indehiscent – fruit remains closed at maturity
 Dehiscent – fruit opens at maturity
Food is confined in the seed
Examples?
Fleshy Fruits
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Juicy, bright colored, attracting-looking
Rely on animals to help disperse seeds
All are indehiscent
Unit 2: Plant Structure & Anatomy
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Much fleshy tissue develops as the ovary changes
Drupe
 Simple, one-seeded
 Example?
Berry
 One or more carpels
 Very fleshy
 Seeds embedded within the flesh of each ovary
 Example?
Pepo
 Large, hard-shelled
 Example?
Unit 2: Plant Structure & Anatomy
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Hesperidium
 Citrus group
 Thick rind
 Fleshy tissue is coordinated in to wedge-shaped pieces
 With/without seeds
Pome
 Fruit surrounds the inedible core parts as it develops
 Example?
Aggregate
 Fleshy
 Develops from a receptacle into simple, true fruits
 Example? strawberry
Unit 2: Plant Structure & Anatomy
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Seeds
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As fertilized egg develops, ovule walls develop
into the seed coat
Unit of dispersal for the new plant
Protection from injury
Nourishment until it can produce own food
Usually one embryo/seed (some may have
multiple)
Typically oval or globular
Wide array of sizes
Unit 2: Plant Structure & Anatomy
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Also vary in color, texture, longevity, method of
dispersal
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Dispersal options
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Covering w/ spines
Hooks
Bristles
Cotton
Plumes
Wings
Unit 2: Plant Structure & Anatomy
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Contains a miniature plant
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Epicotyl
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Hypocotyl
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Lower stem & roots
Surrounded by stored food
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Forms all plant parts above the first node of the stem
Beans = cotyledon
Corn = endosperm
Germination
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Occurs when the seed is softened by water
Under favorable temperature
Unit 2: Plant Structure & Anatomy
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Receives food from its storage
Epicotyl grows upward out of the soil
Hypocotyl grows downward to form roots
The Cell & Its Structure
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Basic structural and physiological unit
Site of chemical reactions that sustain life
Prokaryotes
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Cell without a nucleus
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Have genetic material, but no membrane to encapsulate it
bacteria
Unit 2: Plant Structure & Anatomy
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Reproduction occurs through the transfer of plasmids
No internal organelles
Eukaryotes
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Cells w/ a nucleus
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Genetic material surrounded by a membrane
Found in humans, plants, algae, protozoa
Cell and nuclear membranes
Genetic material will form multiple chromosomes
Plants different from animals:
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Vacuoles
Cell walls
Unit 2: Plant Structure & Anatomy
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Composition
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Chloroplasts
Flagella/cilia?
90% fluid (cytoplasm)
 Free amino acids, proteins, glucose, other
Contents effect genetic expression
Elements of a cell
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59% H
24% O
11% C
4% N
2% other (P, S, etc.)
Unit 2: Plant Structure & Anatomy
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Molecules in a cell
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50% protein
15% nucleic acid
15% carbohydrate
10% lipid
10% other
Cell Structure
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Cell Walls
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Made of hemicellulose
Primary cells may thicken to provide stability
Secondary cell walls: cellulose, lignin, etc.
Unit 2: Plant Structure & Anatomy
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Plasma Membrane
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Protoplast
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Aka – plasmolemma or cytoplasmic membrane
Just inside the cell wall
Protects the cell contents
Semi permeable
Inside of the cell, or cellular contents
Cytoplasm is the liquid portion of the protoplast
Organelles
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Internal structures of the protoplast
Leucoplasts
 Storage of oil, starch, protein
Unit 2: Plant Structure & Anatomy
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Chloroplasts
 Contain chlorophyll used in photosynthesis
 Stores starch
 Contains DNA
Mitochondria
 Site of respiration
 Production of energy – convert usable food sources to
ATP or the most basic energy source
Nucleus
 Contains the chromosomes (DNA) which carries the
genetic code
Vacuoles
 Storage for sugars, starch, salts, pigments, etc.
Unit 2: Plant Structure & Anatomy
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Endoplasmic Reticulum
 Synthesizes protein
 Helps to copy DNA coding
Tissues
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Large group of organized cells of similar structure
that combine to perform a specific function
Meristematic Tissues
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Actively dividing cells that contain new tissues
Found in root and shoot tips, nodes, and cambium
Four categories
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Apical, subapical, intercalary, lateral/cambial
Unit 2: Plant Structure & Anatomy
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Apical Meristems
 At apex of shoot/root
 Produce new buds, leaves, modified parts (flower parts)
 New root extensions
Intercalary Meristems
 Separated by zones of mature tissues
 Just above node, or at base of leaves
 Only found in monocots
Lateral Meristems
 Found laterally along shoots
 Cylinders of actively dividing cells
 Forms conductive tissue that creates the vascular
system (xylem and phloem)
Unit 2: Plant Structure & Anatomy
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Permanent Tissues
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Simple Tissues:
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Simple are uniform w/ only one type of structure
 Typical of epidermal, parenchyma cells
Epidermis Cells
 Single layer of cells on exterior of stems, leaves,
flowers, fruits, and sometimes roots (can be 2-3 layers
thick)
 No pigmentation
 Can elongate to form hairlike structures
Parenchyma
 Thin cells walls w/ large vacuoles
 Contains chloroplast for photosynthesis
Unit 2: Plant Structure & Anatomy
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Complex Tissues:
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Includes conductive system
Move water and solutes around the plant
Xylem
 Conducts water and dissolved nutrients, amino acids,
proteins, sugars
 From roots to aerial plant parts
 Water moves by differences in concentration
Phloem
 Conducts soluble sugars and metabolites (proteins,
hormones, dissolved minerals, salts) from leaves to
other parts of the plant
 Provides short and long-term storage of nutrients
Unit 2: Plant Structure & Anatomy
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Anatomy of Primary Organs
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Primary Roots
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Either one major root, or a root mass
Penetration into soil is done by cell division and
elongation
Root Cap protects the tip of the root
Behind the region of elongation are where root hairs
form
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Increases surface area for absorption
Absorbed nutrients pass into the center of the root and are
sent upward
Unit 2: Plant Structure & Anatomy
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Primary Stems
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Support is provided by various thick-walled cells (usually
found in the xylem)
Turgor (internal water pressure) also provides support
Monocots
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Vascular system usually in scattered bundles
Dicots
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Vascular system arranged in a ring w/ primary xylem on
inside and primary phloem on outside
Vascular cambium (layer of dividing cells) between
Very evident in trees
Unit 2: Plant Structure & Anatomy
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Leaf Structure
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Flat, broad, and thin to provide for maximum light
interception
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Respiration occurs through the leaf stomata
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Can also moderate the amount of light that’s absorbed
Usually on the lower surface
Close at midday to protect plant water
Two layers inside the upper and lower epidermis
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Palisade Cells on upper layer
 Site of photosynthesis
 Tightly packed
Unit 2: Plant Structure & Anatomy
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Spongy tissue on the lower side
Primary & Secondary Growth
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Different from animals, plants tend to grow
continuously
Increases size and provides limited means of
movement
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To more light
To more nutrients
For reproduction
And dispersal
Unit 2: Plant Structure & Anatomy
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Growth happens by production of new cells, and
by subsequent enlargement of those cells
Cells then differentiate into specialized tissues
Primary growth
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Young, herbaceous organs
Increases length of shoots and roots
Monocots and herbaceous dicots
Secondary growth
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Increased girth
Woody layers
Unit 2: Plant Structure & Anatomy
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Cell Division
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Occurs by mitosis where genetic material is exactly
duplicated
Parent cell divides itself to form two exact daughter cells
Interphase
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Resting period between cell divisions
Chromosomes not visible
Nuclear membrane can be seen
Each chromosome makes an exact copy of itself
Prophase
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Identical chromosomes join together
Coil tightly and become visible
Unit 2: Plant Structure & Anatomy
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Metaphase
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Nuclear membrane begins to disappear
No division between nucleus and cytoplasm – nuclear
membrane has faded away
Pairs of identical chromosomes line up on the “metaphase
plate”
Spindle fibers attach to the chromosomes pull them to each
centriole
Anaphase
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Pair separate and are pulled to each centriole
Two groups of identical chromosomes are at opposite ends
of the cell
Unit 2: Plant Structure & Anatomy
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Telophase
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Nuclear membrane begins to reform around both sets of
chromosomes
Chromosomes begin to uncoil and disappear
Cytoplasm separates as a new cell wall forms
“Cell Plate” forms between the two cells
One cell becomes two smaller cells
 Each may grow and divide again
Return to Interphase