Seed Plant Structure and Function

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					Seed Plant Structure and
        Chapter 23
         Seed Plant Overview:
• The plant body consists of two basic parts--- the shoot
  system and the root system
• Shoot system is above ground and includes organs
  such as leaves, buds, stems, flowers, and fruits
• The functions of the shoot system include
  photosynthesis, reproduction, storage, transport, and
  hormone production
• The root system is below ground and includes roots as
  well as modified stem structures such as tubers and
• The functions of the root system include anchorage,
  absorption, storage, transport, and production of
  certain hormones
   Seed Plant Overview Cont.:
• Seed plants contain 2 types of vascular tissue
  (xylem & phloem) to help transport water,
  minerals, & food throughout the root & shoot
• Plant cells have several specialized structures
  including a central vacuole for storage, plastids
  for storage of pigments, and a thick cell wall of
• Plant cells are all box-shaped in appearance
Plant Cell Organization
             • Plant cells are arranged into
               tissues and tissue systems
             • A simple tissue is composed of
               only one type of cell; a complex
               tissue is composed of more than
               one cell type.
             • Plants are composed of
               specialized cells and tissues
             • In plants, the formation of new
               cells, tissues and organs is
               restricted almost entirely to
               regions known as meristems
• There are 3 main types of meristematic
  tissue in vascular seed plants ---- apical,
  intercalary, & lateral meristems
• Apical Meristem occur at
  the tips of roots and
  shoots and are
  responsible for the
  length-wise extension of
  the plant body known as
  primary growth
• Cells in apical meristems
  are produced by mitosis
  & then differentiate into
  specialized cells &
      Intercalary Meristems
• Some monocots, such as grasses &
  bamboo, have intercalary meristems
  located above the bases of leaves and
  stems allowing them to regrow quickly
  after being cut down
           Growth in Plants
• Woody plants have meristem between xylem &
  phloem to produce wood
• Lateral meristems produce outward growth in
  plants or secondary growth
• Lateral meristems are called cambium (cambia,
• Vascular cambium makes wood & vascular
  tissues and cork cambium makes cork & bark
• Plants without lateral meristems have only
  primary, not secondary growth and are called
  herbaceous plants
     Specialized Plant Cells:
• Plants have 3 basic types of cells ---
  parenchyma, collenchyma, &
• Parenchyma cells are the most abundant
  & least specialized
• Parenchyma are loosely-packed, cube
  shaped or elongate cells with a large
  central vacuole & thin cell walls
• Parenchyma cells can specialize
  for various functions (storage,
  photosynthesis, etc.)
• Parenchyma form the bulk of non-woody
  plants such as the fleshy part of an apple
• Collenchyma cells are irregular in shape
  with thicker cell walls & support the
  growing parts of plants
 Collenchyma cell walls are also flexible
  to support new growth regions of the
  plant (example: tough strings on a celery
• Sclerenchyma cells support non-growing parts of plants
  because they have thick, rigid, non-stretchable cell walls
  Sclerenchyma Cells
• Sclerenchyma cells often die at maturity leaving empty,
  box-like structures
• Two types of sclerenchyma cells are fibers & sclereids
• Fibers are cells up to 50cm long that usually occur in
  strands such as linen & flax
  Sclerenchyma Fibers
• Sclereids have thicker cell walls & come in many shapes
• Sclereids may be single cells or groups of cells and give
  pears their gritty texture & give hardness to peach pits &
  walnut shells
               Sclerynchyma Fibers


                 Sclereid Fibers
Other Plant Tissues & Systems:
• Tissues are groups of cells with similar
  structures & functions
• Plants have 3 tissue systems --- ground, dermal,
  and vascular tissues
• Plant tissues make up the main organs of a
  plant --- root, stem, leaf, & flower
• Ground tissue makes up most of the plant's
  body, dermal tissue covers the outside of the
  plant, & vascular tissue conducts water &
                   Dermal Tissue:
• Covers the plant body and
  consists of epidermis in
  young plants & non-woody
  plants that is replaced later
  by periderm in woody plant
• Epidermis is made of
  parenchyma cells in a single
• Epidermis on stem and
  leaves prevents water loss
  by transpiration & produces
  a waxy material called
           Dermal Tissue:
                    • Openings in the
                      epidermis on the
                      underside of a leaf
                      where gases are
                      exchanged are called
                      stomata (stoma, singular)
                    • Sausage-shaped guard
                      cells are found on each
Guard Cells           side of the stoma to help
                      open and close the pore
surrounding stoma     to prevent water loss
                    • Dead cork cells replace
                      epidermis in woody
                      stems & roots
           Ground Tissue:
• Ground tissue constitutes the majority of
  the plant body and contains parenchyma,
  collenchyma, and sclerenchyma cells
• Ground tissue of the leaf (called
  mesophyll) uses the energy in sunlight to
  synthesize sugars in a process known as
• Spongy Mesophyll of Leaf
• Ground tissue of the stem (called pith and cortex)
  develops support cells to hold the young plant upright
• Ground tissue of the root (also called cortex) often
  stores energy- rich carbohydrates
            Vascular Tissue:
• Vascular tissues transport water and dissolved
  substances inside the plant and helps support
  the stem
• The 2 types of vascular tissue are xylem &
• Xylem carries water and dissolved ions from
  the roots to stems and leaves
• Phloem carries dissolved sugars from the
  leaves to all other parts of the plant
• Xylem has 2 kinds of conducting cells ---
  tracheids & vessel elements
            Vascular Tissue:
• Tracheids are long, narrow sclerenchyma cells
  with walls and pits for water to move between
• Vessel elements are short, wide sclerenchyma
  cells without end walls stacked on top of each
• Angiosperms (flowering plants) have tracheids
  & vessel elements, while gymnosperms (cone
  bearers) only have tracheids
• Phloem moves sap (dissolved sugars &
  minerals) from source (where they are made) to
  sink (where they will be used)
               Xylem Cells
Phloem Cells
          Vascular Tissue:
• Phloem is made of cells called sieve tube
  members and companion cells
• sieve tube members are stacked to form
  tubes called sieve tubes with porous
  sieve plates between the cells for
  movement of sugars
• Companion cells are along each sieve
  tube member & help in loading sugar
  into the sieve tube
Root and Shoot system of a plant
              Root System:
• Roots grow underground (subterranean
  part of the plant)
• Roots have 3 main functions --- (1)anchor
  plants (2) absorb and conduct water &
  minerals (3) store food
• The first root to emerge from the most seeds
  is called the primary root or taproot & can
  grow deep to reach water
• Taproots may store food (carrot & beet)
              Root Systems
• Monocots have highly branched, roots called
  fibrous roots that grow near the surface &
  spread out to collect water
• Fibrous roots such as in grasses often help
  prevent erosion
• Adventitious roots grow from a stem or leaf
  above ground in some plants and serve to prop
  up or support the plant (corn)
• Aerial roots obtain water & minerals from the
  air & enable the plant to climb (orchids & ivy)
           Roots 

                             Arial Roots


             Fibrous Roots
       Structure of the Root:
• Root cap covers the apical meristem
  (growth tissue) at the tip of the root &
  produces a slimy substance so roots can
  more easily grow through the ground
• Apical meristem replaces cells of the root
  cap as they are damaged
• Epidermis covers the outside of the root
  & has extensions called root hairs that
  absorb water & minerals and increase the
  surface area of the root
        Structure of the Root:
• The core of the root is called the vascular
  cylinder, contains xylem & phloem
• A band of ground tissue called cortex
  surrounds the vascular cylinder
• A single cell layer called endodermis separates
  the cortex & vascular tissue
• Endodermal cells are coated with a waxy layer
  called the Casparian strip so water is
  channeled into the vascular tissue
• The Pericycle is the outermost layer of central
  vascular tissue & forms lateral roots
    Stem Structure & Function:
• Adapted to support leaves
• Transport water & minerals
• Transport sugars (usually sucrose) from Source (where
  they're made) to Sink (where they're stored)
• Movement of sugars is called translocation
• Store food and/or water
• Tubers (potatoes) underground food storage stems
• Stems grow from the tip or apical meristem
• Stems increase in circumference by lateral meristems
• Leaves are attached to stems at nodes & have lateral
  buds that can develop into new stems or branches
• Internode is space between nodes on a stem
• The tip of each stem usually has a Terminal
  Bud enclosed by specialized leaves called Bud
• Vascular Tissue is arranged in bundles with
  xylem toward the inside & phloem toward the
• Vascular bundles are scattered throughout
  monocot stems
• Vascular bundles are arranged in rings in dicot
              Stem Structure
• Secondary grow
  (woody growth)
  occurs in dicots, but
  less often in
• Plants with only
  primary growth
  (non-woody) are
  called herbaceous
• Darker wood in the center of a tree trunk is
  called Heartwood and is composed of old, non-
  functional xylem
• New, functional xylem makes up lighter wood
  in the tree trunk and is called Sapwood
• Sapwood gets wider, but heartwood remains
  the same size
• Bark is the protective covering of Woody
  Plants & consists of Cork, Cork Cambium, and
     Translocation of Sugars:
• Phloem cells move sugars through a plant
• Sugars made in photosynthetic cells are
  PUMPED into Sieve Tubes by ACTIVE
  TRANSPORT at the Source
• Turgor Pressure Increases as Water enters the
  Sieve Tube by Osmosis
• TURGOR moves the SAP toward the SINKS
• Known as the PRESSURE-FLOW
          Transport of Water:
• Transport of Water and mineral Nutrients occurs in the
• Water movement in plants is driven by Transpiration
  (evaporation of water from leaves & stems)
• As water evaporates, more water is pulled into the
• Transpiration produces a NEGATIVE pressure in the
  xylem pulling water UPWARD
• Water molecules are cohesive (attracted to each other)
  which also pulls water upward
• Water is also adhesive sticking to the walls of the
• Known as Cohesion Theory of water movement
   Leaf Structure & Function:
• Flat surfaces helps leaves capture
  sunlight for photosynthesis
• Convert carbon dioxide and water into
  simple sugars (glucose)
• Some leaves store food (onion) and water
• Protect (cactus spines)
• Used Dyes, Fibers, Fuels, Drugs, Wax,
  Soap, Spices and Food
    Leaf Structure & Function:
• Attached by a stem-like petiole to the plant
• Simple leaves have one blade, while
  compound leaves have several leaflets
• Covered with a single layer of cells called
  epidermis (upper & lower)
• A waxy cuticle prevents water loss
• Openings called stomata on the underside of
  leaves for gas exchange (CO2 & O2)
• Two guard cells on either side of the stomata
  open & close the openings
• Two guard cells on
  either side of the
  stomata open & close
  the openings
• When guard cells
  LOSE water, the
  stoma CLOSE, while
  the stoma OPEN
  when guard cells
  gain water & swell
• Stomata are CLOSED during the HOTTEST parts of
  the day to prevent water loss from leaves
• Below the epidermis are 2 types of chlorophyll
  containing MESOPHYLL cells ---palisade & spongy
• PALISADE mesophyll cells are closely packed
  columnar cells (most photosynthesis occurs here)
• SPONGY mesophyll cells are loosely packed with air
  spaces containing CO2 & O2
• VASCULAR BUNDLES (xylem & Phloem) in the
  spongy mesophyll appear as VEINS on the surface of
  the leaf
• VENATION is the
  arrangement of veins in
  a leaf
• Monocots leaves (such as
  Grasses or Corn Plants)
  have Parallel Venation
• Dicots leaves form a
  Branched network called
  Net Venation
• In carnivorous plants
  (Venus Fly Trap), the
  leaves trap insects for
  food so the plant can get
  enough nitrogen (grow
  in N2 poor soil)

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