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Plant Structure, Reproduction, and Development

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Chapter 31 Plant Structure, Reproduction, and Development – PowerPoint PPT presentation

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Title: Plant Structure, Reproduction, and Development


1
Chapter 31
  • Plant Structure, Reproduction, and Development

2
  • Plants are essential to human life.
  • Our use of plants parallels the growth of
    civilization.
  • Some plants, such as coastal redwoods, are among
    the largest and oldest organisms on earth.
  • Coast redwoods are gymnosperms, a kind of plant
    that bears seeds on cones

3

Man climbing a redwood tree.
4
Most plants are angiosperms which will be the
focus of this discussion on plant structure.
5
Angiosperms
  • Angiosperms, or flowering plants, bear seeds in
    fruits.

6
Two Main Groups of Angiosperms
  • Monocots and Eudicots
  • They differ in
  • number of seed leaves (cotyledons)
  • leaf venation
  • arrangement of vascular system in stems
  • number of flower parts
  • root structure

7
  • Lily Monocot
  • Rose Eudicot

8
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9
  • Monocots
  • one cotyledon
  • parallel leaf venation
  • scattered vascular bundles
  • flower parts in 3s or multiples of 3
  • fibrous roots

10
  • Eudicots
  • two cotyledons
  • branched leaf venation
  • ring of vascular bundles
  • flower parts in 4s or 5s (or multiples)
  • taproot system

11
Monocot or Eudicot?
12
Typical Plant Body
  • Three basic organs several types of tissues
    that perform a particular function.
  • Roots
  • Stems
  • Leaves

13
  • Plants must draw resources from two different
    environments.
  • They must draw water and minerals from the soil
    and CO2 and sunlight from aboveground.
  • Neither roots nor shoots can survive without the
    other.

14
  • Plants absorb water and minerals from soil
    through roots.
  • Plants absorb the suns energy and carbon dioxide
    from the air through shoots (stems and leaves).

15
  • Plant roots depend on shoots for carbohydrates
    produced via photosynthesis.
  • Plant shoots depend on roots for water and
    minerals.

16

17
Root System
  • Anchors the plant in the soil.
  • Absorbs and transports minerals.
  • Stores food.

18
  • Monocots
  • Dicots

19
Root Hairs
  • Found in both monocots and dicots.
  • Increase surface area enormously.
  • Cotyledons

20
Shoot System
  • Made up of stems, leaves, and adaptations for
    reproduction (flowers in angiosperms).
  • Stems above ground and support the leaves and
    flowers.
  • Nodes areas on the stems at which leaves are
    attached.

21

22
Two Types of Buds
  • Terminal Bud where a plant stem grows in
    length.
  • Produces hormones (auxins) that inhibit the
    growth of the lateral buds (apical dominance).

23
Apical Dominance
  • Concentrates resources on height.
  • Evolutionary adaptation that increases the
    plants exposure to height.
  • Some axillary buds become flowers.

24
Modified Roots, Stems, and Leaves
Modified stems used for reproducing asexually.
Used for food storage and asexual reproduction.
25
Modified Leaves - Tendrils
26
Purposes of Leaf Modifications
  • Protection
  • Cactus spine or rose thorns.
  • Climbing
  • Tendrils on pea plants or clematis.

27
Three Tissue Systems Plant Body
  • Dermal Tissue
  • Ground Tissue
  • Vascular Tissue

28

29
Dermal Tissue
  • Forms an outer protective covering.
  • In many plants, it has a waxy covering to prevent
    water loss.
  • Acts as a first defense against damage and
    disease.
  • Usually a single layer of packed cells called the
    epidermis.

30
Stomata
  • Openings in the epidermis (pores) that enable gas
    exchange.
  • Usually found on the underside of the leaf.
  • Are opened and closed by guard cells.

31

32
Vascular Tissue
Xylem and Phloem
33
Vascular System
  • Analogous to our circulatory system.
  • Xylem dead cells that function to transport
    water from the roots to the aboveground plant.
  • Phloem living cells that function to transport
    sugars from the aboveground plant to the roots.

34
  • Phloem
  • Xylem

35
Ground Tissue
  • Lies between dermal and vascular tissue.
  • Analogous to connective (muscle) tissue.
  • Eudicot ground tissue divided into pith and
    cortex.
  • Leaf ground tissue called mesophyll.

36
Three Structures that Distinguish Plant Cells
from Animal Cells.
Chloroplast
Water-Filled Vacuole
Cell Wall
37
Five Types of Plant Tissues
  • Parenchyma cells
  • Collenchyma cells
  • Sclerenchyma cells
  • Water-conducting cells (Xylem)
  • Food-conducting cells (Phloem)

38
Parenchyma Cells
Function in photosynthesis, metabolism, and food
and water storage.
39
Collenchyma Cells
Have thick cells walls that give herbaceous
plants their structure.
40
Sclerenchyma Cells
  • Fibrous lignified cells.
  • Gives pears their grittiness.
  • Make up seed coats.

41
Sclerenchyma
  • Sclerenchyma cells
  • Thick secondary cell wall containing lignin
  • Lignin is a main component of wood
  • Dead at maturity
  • Rigid support
  • Two types of sclerenchyma cells are fibers and
    sclereids
  • Fiberslong and thin, arranged in bundles
  • Sclereidsshorter than fibers, present in nut
    shells and pear tissue

42
Water-Conducting Cells
  • Tracheids and vessel elements that move water
    from the roots to the stomata in the leaves.
  • Both have thick secondary cell walls
  • Both are dead at maturity
  • Chains of tracheids and vessel elements form
    tubes that make up the vascular tissue called
    xylem

43
Xylem
44
Food Conduction Cells
  • Sieve tube members move nutrients both ways
    (roots to leaves and leaves to roots).
  • No secondary cell wall
  • Alive at maturity but lack most organelles
  • Companion cells
  • Contain organelles
  • Control operations of sieve tube members
  • Chains of sieve tube members, separated by porous
    sieve plates, form the vascular tissue called
    phloem

45
Phloem
46
Primary Growth Lengthen s Roots and Shoots
  • Unlike animals, plant growth is indeterminate
  • Growth occurs throughout a plants life
  • Plants are categorized based on how long they
    live
  • Annuals complete their life cycle in one year
  • Biennials complete their life cycle in two years
  • Perennials live for many years

47
Primary Growth Lengthen s Roots and Shoots
  • Plant growth occurs in specialized tissues called
    meristems
  • Meristems are regions of active cell division
  • Apical meristems are found at the tips of roots
    and shoots
  • Primary growth occurs at apical meristems
  • Primary growth allows roots to push downward
    through the soil and shoots to grow upward toward
    the sun

48
Two Types of Growth
  • Going Deeper
  • Primary Getting Taller

49
Primary Growth of a Root
Zone of Elongation Cells can lengthen by as much
as 10 times.
Zone of Maturation Cells differentiate into
dermal, vascular, and ground tissue.
50
Primary Growth of a Shoot
  • The apical meristems of shoot tips occur as buds
    at the stem tip and at the base of leaves
  • Cells produced in the shoot apical meristem
    differentiate into dermal, vascular, and ground
    tissues
  • Vascular tissue produced from the apical meristem
    is called primary vascular tissue (primary xylem
    primary phloem)

51

52
Secondary Growth Increases Girth
  • Secondary growth occurs at lateral meristems
  • Lateral meristems are areas of active cell
    division that exist in two cylinders that extend
    along the length of roots and shoots.
  • Vascular cambium is a lateral meristem that lies
    between primary xylem and phloem.
  • Cork cambium is a lateral meristem that lies at
    the outer edge of the stem cortex.

53
Secondary Growth Increases Girth
54
Sexual Reproduction of Flowering Plants
  • Flowers typically contain four types of highly
    modified leaves called floral organs
  • Sepalsenclose and protect flower bud
  • Petalsshowy attract pollinators
  • Stamensmale reproductive structures
  • Carpelsfemale reproductive structures
  • Memory Hint Stamens - male

55

Anther - produces pollen which develops into sperm
Stigma - site of pollination
Ovary - houses ovules, which contain developing
eggs
56
Angiosperm Life Cycle Overview
  • Fertilization occurs in the ovule the fertilized
    egg develops into an embryo encased in a seed.
  • The ovary develops into a fruit, which protects
    the seed and aids in dispersal.
  • The seed germinates under suitable conditions to
    produce a seedling, which grows into a mature
    plant.

57
Life Cycle of a Angiosperm
58
Development of Pollen and Ovules Culminates in
Fertilization
  • Plant life cycles involve alternating diploid
    (2n) and haploid (n) generations.
  • The diploid generation is called the sporophyte.
  • Specialized diploid cells in anthers and ovules
    undergo meiosis to produce haploid spores
  • The haploid spores undergo mitosis and produce
    the haploid generation
  • The haploid generation is called the gametophyte.
  • Gametophytes produce gametes via mitosis.

59
Male Gametophyte
  • The male gametophyte is a pollen grain.
  • A cell in the anther undergoes meiosis to produce
    four haploid spores.
  • Each spore divides via mitosis to produce two
    cells called the tube cell and generative cell.
  • A tough wall forms around the cells to produce a
    pollen grain.
  • Pollen grains are released from the anther.

60
Female Gametophyte
  • The female gametophyte is an embryo sac.
  • A cell in the ovule undergoes meiosis to produce
    four haploid spores
  • Three of the spores degenerate
  • The surviving spore undergoes a series of mitotic
    divisions to produce the embryo sac.
  • One cell within the embryo sac is an egg ready
    for fertilization.
  • One central cell within the embryo sac has two
    nuclei and will produce endosperm.

61

62
Development of pollen and ovules culminates in
fertilization.
  • Pollination
  • Transfer of pollen from anther to stigma.
  • Pollen is carried by wind, water, and animals.
  • Pollen grain germination
  • Tube nucleus produces pollen tube, which grows
    down through the style to the ovary.
  • Generative nucleus divides to produce two sperm.

63
  • Double fertilization
  • One sperm fertilizes the egg to produce a zygote.
  • One sperm fuses with the central cell nuclei to
    produce 3n endosperm.
  • Endosperm (3n) nourishes the developing embryo.

64

65
The Ovule Develops into a Seed
  • The zygote divides many times via mitosis to
    produce the embryo.
  • The embryo consists of tiny root and shoot apical
    meristems and one or two cotyledons.
  • A tough seed coat develops.
  • Seed dormancy
  • Embryo growth and development are suspended
  • Allows delay of germination until conditions are
    favorable

66

Endosperm Food for the Embryo
67
Pea Flower to Peas Seeds
68
Seed Germination Completes the Life Cycle
  • Germination breaks seed dormancy.
  • Germination begins when water is taken up.
  • Eudicot seedling shoots emerge from the soil with
    the apical meristem hooked downward to protect
    it.
  • Monocot seedling shoots are covered by a
    protective sheath and emerge straight from the
    soil.
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