Unit 2: Plant Structure & Anatomy Chapters 3 & 4.

Unit 2: Plant Structure & Anatomy

Chapters 3 & 4

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


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


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


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


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.)


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


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


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


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.


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?


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


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


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


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


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


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


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


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


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


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


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


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?


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


Also vary in color, texture, longevity, method of dispersal Dispersal options

Covering w/ spines Hooks Bristles Cotton Plumes Wings


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


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


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


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.)


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.


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


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.


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


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)


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


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


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


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


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


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


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


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


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

Unit 2: Plant Structure & Anatomy Chapters 3 & 4.

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Transcript of Unit 2: Plant Structure & Anatomy Chapters 3 & 4.