Plant Structure and Growth Chapter 35

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Plant Structure and GrowthChapter 35
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The Angiosperm Body
Two Classes based on Embryo s 1. Monocots
single Cotyledon (seed leaf) 2. Dicots two
cotyledons

• Three Basic Organs
• Roots
• Stems/Shoots
• Leaves

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Monocots vs. Dicots
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Root System
Dicots have main Taproot one large vertical
root, small lateral roots, firm anchor. Energy
storage Root crops harvested before flowering
Monocots fibrous roots, thread like, short,
Root Hairs tiny fibers increase surface area,
have Mycorrhizae.
Adventitious roots roots that rise up above
ground, or other unusual area
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Shoot System
Modified Shoots

• Vegetative shoots with leaves, floral shoots
• May be
• Vegetative (leaf bearing)
• Reproductive (flower)
• Stems
• Nodes point where leaves are attached
• Internode b/w nodes
• Auxillary Bud
• Terminal Bud
• Apical Dominance
• Apical Meristem

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Leaves
Modified

• Blade leaf structure, photosynthesis
• Petiole stalk that joins leaf w/ node of stem

Grasses lack petiole Monocots have parallel
veins in leaves, Dicots have multi-branched
network. Pattern can be used to ID plant.
Specialized for photosynthesis or other functions
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Three Systems of Tissues

1. Dermal Tissue System epidermis, covers and
   protects. Root hairs, cuticle of leaves secrete
   waxes.
2. Vascular Tissues Systems Xylem, Phloem
3. Ground Tissue Systems b/w dermal and vascular
   tissues. Mostly parenchyma.

• Xylem moves water/minerals upwards from root
• Phloem moves food from leaves to roots

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Water/Food Conducting Cells

• Xylems elongated cells to conduct water. Two
  types
• 1. Tracheids long thin, tapered
• 2. Vessel elements wider, shorter, end to end
• Both dead at maturity, Various sections
• Pits thin regions of primary walls, found in
  tracheids
• Xylem vessels end walls perforated, water flows
  freely

Phloem food conducting sieve tube members, no
nucleus Chains of Sieve-tube members alive at
maturity, Angiosperms have sieve plates b/w
cells w/ pores. Each sieve tube member has
companion cells,connected to sieve tube by
plasmodesmata, helps ST and loads sugar into
phloem.
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Basic Structure of Plant Cell

• General Structure of cell with modifications.
• Cell Wall (Primary, Secondary (3), Lamella)
• Chloroplast
• Vacuole
• Tonoplast
• Plasmodesmata

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Specialized Structure/Function

• Protoplast contain chloroplasts for
  photosynthesis, cell content exclusive of cell
  wall
• Parenchyma Cells least specialized, primary
  cell wall, lack secondary wall, performs main
  metabolic function, starch storage in plastids,
  vacuole, typical cell, exceptions seive tubes,
  retain ability to differentiate
• Collenchyma Cells thick primary cell walls,
  grouped in strands/cylinders for support. Lack
  secondary walls, no lignin, no restraint in
  growth, support (young stems/petioles)
• Sclerenchyma Cells support with secondary walls
  (lignin). rigid, cannot elongate, occur in areas
  where growth has stopped in length, dead at
  maturity (skeleton, xylem dual func.)
• Fibers long slender, tapered, occurs in
  bundles,
• Sclereids short, irregular shape, seeds,
  nutshells,

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Growth
Annuals/Perennials Meristems Apical Meristems

• Primary Growth elongation of AM in tips of
  roots/buds.
• Secondary Growth thickening of roots/shoots
  (lateral meristems)
• Quiescent Center cells divide slowly in AM.
  function as reserves
• Primary Meristemsprotoderm, procambium, ground
  meristem (produce 3 tissues of root dermal,
  vascular, and ground)

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Early Winter Deciduous Tree
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Primary growth of roots
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Root Tissues

• Protoderm
• gives rise to outermost meristem, epidermis,
  single layer of cells covering roots
• Procambrium
• Stele develop from procambrium, xylem/phloem
  vascular bundle development. Single central
  cylinder, xylem radiates out, phloem forms
  around.(Pith in monocots).
• Ground
• Cortex b/w stele and epidermis, ground tissue
  development.
• Endodermis innermost layer of cortex, one cell
  thick
• Pericycle layer of cells that may become
  meristmatic, produces lateral roots.

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Primary Growth of Shoots

• Apical Meristem dome shape, terminal end of
  bud. Gives rise to protoderm, procamrium, and
  ground meristem
• Axillary Buds meristem islands that will form
  branches later on.
• Lateral roots develop from w/i main root, Lateral
  branches develop from axillary buds.
• Vascular tissue located near surface.

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Primary Tissue of Stems

• Vascular Tissues/Vascular Bundles lengthwise in
  stem, grouped in bundles in center and spread
  outwards, (roots found in center). Surrounded by
  ground tissue.
• Dicots arranged in rings w/ piths and cortex
  external to ring. Xylem face towards pith.
  Phloem face cortex.
• Monocots VB scattered in ground tissue. Ground
  tissue mostly parenchymal cells.
• Sclerenchyma Cells form fibers for support

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Tissue Organization of Leaves

• Epidermis
• covered by dermal cells, interlocking cells.
• Has stomatas tiny pores flanked by guard cells
  (epithelial cells).
• Transpiration loss of water by evaporation.
• Upper and Lower regions
• Mesophyll paranchymal cells b/w upper and lower
  epidermal layers
• Chloroplasts
• Distinct regions in Dicots
• Palisade cells
• Spongy Parenchyma spongy, air space, CO2 and O2
  circulates, gas exchange
• Vascular Bundle Xylem, Phloem and Fibers for
  support

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Secondary Growth

• Secondary plant body tissue produced during
  secondary growth in diameter. Two Lateral
  Meristem Functions
• Vascular Cambium produces secondary vascular
  bundle
• Xylem produced towards interior
• Phloem produced towards exterior
• Forms from paranchymal cells, b/come meristemic
• Cork Cambium produces tough thick covering for
  stems and roots. Replaces epidermis.
• Cork waxy substance, suberin. Die early,
  barrier
• Periderm cork and cork cambium
• Bark secodary phloem, cork cambium, cork
• (phloem and periderm)

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Cork Cambium Production of Periderm

• Cork Cambium produces cork cells (waxy).Fixed
  size. Cork acts as barrier.
• Periderm cork cork cambrium.
• Bark all tissue external to vascular cambrium
• Lenticels areas of bark which is spongy, gas
  exchange for cellular respiration.

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Growth and Development

• Growth
• Morphogenesis
• Tissue/organs
• Differentiation
• Cellular diversity

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Growth
Plane directional growth Asymmetrical Growthone
daughter cell receives more of cytoplasm Guard
Cells need both asym., and plane
division Preprophase Band microtubules in
cortex set plane of division