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Plant structure and reproduction

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					Plant Structure,
Reproduction, and
Development
                  Angiosperms

•   Cotyledons – embryonic leaves
•   Monocot – one embryonic leaf
•   Dicot – two embryonic leaves
•   Differences between Monocots & Dicots
    –   Veins are parallel /branched
    –   Vascular bundles complex /ring
    –   Leaves arranged in multiples of 3 /multiples of 4 or 5
    –   Fibrous roots /taproot
         SEED LEAVES      LEAF VEINS             STEMS               FLOWERS               ROOTS

MONOCOTS




         One                Main veins     Vascular bundles in     Floral parts usually    Fibrous
         cotyledon      usually parallel   complex arrangement     in multiples of three   root system



DICOTS




         Two                 Main veins    Vascular bundles      Floral parts usually in   Taproot
         cotyledons    usually branched    arranged in ring      multiples of four or five usually present
                                                                                                         Figure 31.2
           Angiosperms

• Most angiosperms are dicots
• This group includes shrubs, trees (except
  conifers), and many of our food crops
• Monocots include orchids, bamboos,
  palms, lilies, and grains and grasses.
               Plant Body
• Root system – anchors the plant into the soil
   – Roots have root hairs – outgrowth of
     epidermal cells
   – Shoot system – part of plant above ground
     stems – support leaves and grounded
     nodes – points where leaved are attached
     leaves – main site of photosynthesis
     terminal bud – node at tip of plant;
     responsible for growth lengthwise; apical
     dominance (inhibits growth of axillary buds)
     axillary buds – located in angles formed by
     the leaf; usually dormant; causes the plant to
                               Terminal bud




                Blade
         Leaf
                                                              Flower
                Petiole
                Axillary bud


                Stem
SHOOT
SYSTEM




                                                  Node

                                                  Internode




                Taproot                       Root
                                              hairs
ROOT
SYSTEM



                                                                       Figure 31.3
                 Modified Roots and
                 Shoots          STRAWBERRY
                                 PLANT
• Modified taproots –
  sweet potatoes, sugar
  beets, & carrots/ stores                              Runner
  starch
   – Uses this stored sugar                        POTATO
                                                   PLANT
     source for active growth
     and producing flowers and
     fruit                                                                   Rhizome

• Modified Stems                 IRIS
   – runner – horizontal stem    PLANT

   – rhizomes – horizontal stem               Rhizome
     underground
                                                                     Tuber
                                                           Taproot
   – tubers – white potatoes    Root
     that are at the end of
     rhizomes that store sugar
                Modified Roots and
                Shoots
• Modified leaves
  –   Grasses have no petioles
  –   Celery have enormous petioles that we eat
  –   Tendrils have coiled tips which aid in climbing
  –   Cactus have spines
            Plant Tissue Systems

• Epidermis
  – Covers and protects
  – First line of defense
  – Cuticle is the waxy substance that helps
    plants to retain water
• Vascular System
  – xylem/phloem – transports water and
    nutrients
  – support
           Plant Tissue System

• Ground Tissue System
  – Filling spaces, bulk
  – Parenchyma, collenchyma, sclerenchyma
  – Photosynthesis, storage, support
                  Plant Tissue System
• Roots
  – Epidermis
     •   Covers roots
     •   Entrance for water and nutrients
     •   May form root hairs
     •   No cuticle
  – Ground tissue
     • Cortex – parenchyma, store food
     • Endodermis – selective barrier, thin layer of cells decides what
       passes between vascular tissue and cortex
  – Vascular Bundles
     • xylem – spokes of wheel
     • phloem – fills in wedges between spokes
VASCULAR     Xylem
TISSUE
SYSTEM
             Phloem




Epidermis




    GROUND       Cortex
    TISSUE
    SYSTEM      Endodermis

                             Figure 31.6B
                Plant Tissue System
• Leaf
  – Epidermis
     • Covered by cuticle
     • Small pores called stomata
     • Surrounded by guard cells
  – Ground Tissue
     • Mesophyll composed of parenchyma cells and chloroplast
     • Air located in spaces between cells
  – Vascular System
     • Vein – composed of xylem and phloem surrounded by
       parenchyma cells
Figure 31.6D
                Plant Tissue System
• Stem
  – Epidermis
     • Thin layer of cells
     • Covered by cuticle
  – Ground Tissue
     • Dicot - 2 parts / Monocot – 1 part (ground tissue)
         – Pith – food storage
         – Cortex – fills spaces
  – Vascular Tissue
     • Occurs in vascular bundles
         – Dicot – ring
         – Monocot - random
Figure 31.6C
             Plant Cells

• Three main
  differences between
  animal cells and
  plants cells are
  – Cell wall
  – Central vacuole
  – chloroplasts




                           Figure 31.5A
                  Plant Cells

Five Major Types of Plant Cells
    1. Parenchyma cells – most abundant type
     •     Remain alive at maturity
     •     Primary cell wall (thin)
     •     Function in food storage and photosynthesis
     •     Multisided
     2.   Collenchyma cells
           primary cell wall (thick)
           alive at maturity
           provide support in plants that are still growing
Parenchyma Cells




      Primary
      wall
      (thin)




Pit




                   Figure 31.5B
                  Plant Cells

3. Sclerenchyma cells
  –   Rigid secondary walls
  –   Hardened with lignin
  –   Found in regions that is not growing
  –   Dead at maturity
  –   Two types of sclerenchyma cells
       • Fiber – long and slender and occurs in bundles; hemp fibers
         make rope
       • Sclereid – stone cell; short, irregular shaped secondary wall;
         found in nutshells and sead-coats
       Sclerenchyma Cells




Pits


                Secondary
                wall


                  Fiber
                  cells


            Primary
            wall

        FIBER
                            Figure 31.5D
                  Sclerenchyma Cells
Sclereids (stone cells)


        Secondary            Sclereid
        wall                 cells




        Primary                 Pits
        wall
                  SCLEREID




                                        Figure 31.5D continued
                  Plant Cells
4. Water-Conducting cells
   – Rigid, lignin-containing
                                                  Pits
     secondary cell walls                                          Tracheids

   – Cells are dead at maturity                   Vessel element

   – Hollow in the middle
   – Functions in support
   Two types of water-
     conducting cells
                                                                               Pits
        1. Tracheids – long cells   Openings
                                    in end wall
     with tapered
          ends
        2. Vessel Elements –
     wide, short cells
            Plant Cells

5. Food – Conducting cells (sieve tube
   members)
     -arranged end to end
     - thin primary walls with no secondary wall
     -alive at maturity
     -transports sugars and minerals
     -sieve plates – located at the ends of the
     sieve tube members
Sieve Tube Members

  Sieve plate


      Companion
      cell




          Cytoplasm

Primary
wall
            Primary Growth

• Indeterminate growth – continue to grow
  as long as they live
  – Annuals – wheat, corn, rice
  – Biennials – beets, carrots
  – Perennials – trees, shrubs, grasses
            Primary Growth

• Apical meristem – lengthwise growth
• Root cap – protects apical meristem in
  roots
• Two functions of root apical meristem
  – Replaces cells of root cap
  – Produces cells for primary growth
               Primary Growth

• Three regions of roots
  – Epidermis (outermost)
  – Cortex (bulk)
  – Vascular tissue
• Elongation
  – uptake of water
  – cellulose fibers extend (accordion)
  – forces roots into soil
• Differentiation – caused by master gene; causes
  unspecialized cells to specialize
                                       Vascular   Cortex
                                       cylinder        Epidermis




 DIFFERENTIATION
                                                        Root hair
 ELONGATION




                   Cellulose
                   fibers
DIVISION
  CELL




                     Apical meristem
                     region
                                                         Root
                                                         cap

                                                                    Figure 31.7B
             Primary Growth

• Three Zones
  – Cell division
  – Elongation
  – Differentiation
              Flower Reproduction


• The angiosperm
                                             Anther
                     Carpel     Stigma

  flower is a
  reproductive          Ovary


  shoot consisting
  of
  – sepals
  – petals
                                                          Stamen



  – stamen
  – carpels
                                     Ovule            Sepal

                      Petal

                                                              Figure 31.9A
             Fertilization of an
             Angiosperm
• Formation of a pollen grain
  – Cells that make pollen grains are located in
    the anther
  – Meiosis- four haploid spores that eventually
    form two haploid cells called a tube cell and a
    generative cell
  – Wall forms around the two cells known as a
    pollen grain
  – Animals, wind, and water transport pollen
    grain (male gametophyte)
            Fertilization of an
            Angiosperm
• Formation of an Egg Cell
  – Megaspore mother cell – forms 4 haploid
    megaspores and three degenerate
  – Surviving megaspore enlarges/ mitotic
    division
  – End Result – One large cell with two haploid
    nuclei and six smaller cells.
  – One of the six smaller cells is the haploid
    egg.
              Pollination

  Sugar/enzymes on stigma causes tube cell to
  grow and form pollen tube
• Both cells (generative cell and tube cell) travel
  to embryo sac
• Generative cell forms two sperm cells
• One sperm cell fertilizes the nucleus with the
  polar nuclei (triploid nucleus/3n)
              Pollination

• One sperm cell fertilizes egg cell (diploid
  nucleus/2n)
• Triploid forms endosperm/functions to nourish
  embryo (popcorn)
• Flowering plants (double fertilization)
• Alternation of generations
  – Haploid – female gametophytes (ovules/egg), male
    gametophytes (generative cell/sperm)
  – Diploid – sporophyte (plant/flower); produces haploid
    spores by meiosis

				
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