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Unit 2: Plant Structure & Anatomy Unit 2 Objectives:
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 Plan of the Entire Plant
Focus on the Angiosperm (seed enclosed in a fruit) Monocot – one seed leaf Dicot – two seed leaves
Roots Anchor Absorb water & nutrients – transport to the stem Store food produced by the aboveground part of the
plant
Unit 2: Plant Structure & Anatomy
Major parts of the root system: 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?
Unit 2: Plant Structure & Anatomy 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
Stems Helps form the major aboveground structure of the plant Attachment point for leaves, flowers, and fruit Contains the vascular system
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
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)
Develops from a bud to bear leaves and more buds Swelled points called nodes
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
Types of stems: 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
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 Leaves
Main function is to make food and other chemicals (proteins, fats, oils) used for growth/reproduction Any part of the green plant can also do this
Parts of the leaf 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
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
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
Flowers Reproductive part of angiosperms Complete flowers contain both male and female organs
Male Stamen Produces pollen
Female Pistil Receives pollen and forms seeds
What are some examples?
Unit 2: Plant Structure & Anatomy
Separate flowers Male and female parts both on same plant, but in different
locations What is an example?
Other flowers 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
Inflorescense Arrangements of flowers or groups of flowers on a plant Diversity in the arrangement
Flower Positions 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 Flower Parts
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 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
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
Essential Organs 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
Stamens may be opposite or alternate w/ the petals Pistils
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
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
Flower Classification By presence/absence of parts Complete Flowers
Calyx, corolla, stamen, pistil Four “regular” parts
Incomplete Flowers Lack one or more of the previous four
Perfect Flowers Both stamen & pistil May lack sepals or petals
Unit 2: Plant Structure & Anatomy
Imperfect Flowers Lack either stamen or pistil May/may not have sepals or petals
Naked Flowers No petals or sepals
Apetalous Flowers No petals
Staminate Flowers Have stamen(s) No pistils
Pistillate Flowers Have pistil(s) No stamen
Unit 2: Plant Structure & Anatomy
Terms used to describe flowering characteristics 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
Flower Forms 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 Protection for seed Means of dispersal Ripened, seed-bearing ovaries of flowers
Unit 2: Plant Structure & Anatomy
Dry fruits 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 Juicy, bright colored, attracting-looking Rely on animals to help disperse seeds All are indehiscent
Unit 2: Plant Structure & Anatomy
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
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 Seeds
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
Also vary in color, texture, longevity, method of dispersal Dispersal options
Covering w/ spines Hooks Bristles Cotton Plumes Wings
Unit 2: Plant Structure & Anatomy
Contains a miniature plant Epicotyl
Forms all plant parts above the first node of the stem Hypocotyl
Lower stem & roots Surrounded by stored food
Beans = cotyledon Corn = endosperm
Germination Occurs when the seed is softened by water Under favorable temperature
Unit 2: Plant Structure & Anatomy
Receives food from its storage Epicotyl grows upward out of the soil Hypocotyl grows downward to form roots
The Cell & Its Structure Basic structural and physiological unit Site of chemical reactions that sustain life Prokaryotes
Cell without a nucleus Have genetic material, but no membrane to encapsulate it
bacteria
Unit 2: Plant Structure & Anatomy
Reproduction occurs through the transfer of plasmids No internal organelles
Eukaryotes Cells w/ a nucleus
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:
Vacuoles Cell walls
Unit 2: Plant Structure & Anatomy
Chloroplasts Flagella/cilia?
Composition 90% fluid (cytoplasm)
Free amino acids, proteins, glucose, other Contents effect genetic expression Elements of a cell
59% H 24% O 11% C 4% N 2% other (P, S, etc.)
Unit 2: Plant Structure & Anatomy
Molecules in a cell 50% protein 15% nucleic acid 15% carbohydrate 10% lipid 10% other
Cell Structure Cell Walls
Made of hemicellulose Primary cells may thicken to provide stability Secondary cell walls: cellulose, lignin, etc.
Unit 2: Plant Structure & Anatomy
Plasma Membrane Aka – plasmolemma or cytoplasmic membrane Just inside the cell wall Protects the cell contents Semi permeable
Protoplast Inside of the cell, or cellular contents Cytoplasm is the liquid portion of the protoplast
Organelles Internal structures of the protoplast Leucoplasts
Storage of oil, starch, protein
Unit 2: Plant Structure & Anatomy
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
Endoplasmic Reticulum Synthesizes protein Helps to copy DNA coding
Tissues Large group of organized cells of similar structure
that combine to perform a specific function Meristematic Tissues
Actively dividing cells that contain new tissues Found in root and shoot tips, nodes, and cambium Four categories
Apical, subapical, intercalary, lateral/cambial
Unit 2: Plant Structure & Anatomy
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
Permanent Tissues Simple Tissues:
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
Complex Tissues: 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 Anatomy of Primary Organs
Primary Roots 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 Increases surface area for absorption Absorbed nutrients pass into the center of the root and are
sent upward
Unit 2: Plant Structure & Anatomy
Primary Stems Support is provided by various thick-walled cells (usually
found in the xylem) Turgor (internal water pressure) also provides support Monocots
Vascular system usually in scattered bundles Dicots
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
Leaf Structure Flat, broad, and thin to provide for maximum light
interception Can also moderate the amount of light that’s absorbed
Respiration occurs through the leaf stomata Usually on the lower surface Close at midday to protect plant water
Two layers inside the upper and lower epidermis Palisade Cells on upper layer
Site of photosynthesis Tightly packed
Unit 2: Plant Structure & Anatomy
Spongy tissue on the lower side
Primary & Secondary Growth Different from animals, plants tend to grow
continuously Increases size and provides limited means of
movement To more light To more nutrients For reproduction And dispersal
Unit 2: Plant Structure & Anatomy
Growth happens by production of new cells, and by subsequent enlargement of those cells
Cells then differentiate into specialized tissues Primary growth
Young, herbaceous organs Increases length of shoots and roots Monocots and herbaceous dicots
Secondary growth Increased girth Woody layers
Unit 2: Plant Structure & Anatomy
Cell Division Occurs by mitosis where genetic material is exactly
duplicated Parent cell divides itself to form two exact daughter cells Interphase
Resting period between cell divisions Chromosomes not visible Nuclear membrane can be seen Each chromosome makes an exact copy of itself
Prophase Identical chromosomes join together Coil tightly and become visible
Unit 2: Plant Structure & Anatomy
Nuclear membrane begins to disappear Metaphase
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 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
Telophase 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
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