The Plant Body

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The Plant Body
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Why are plants so vital?Because Plants are
Producers.
Van Helmont - 1648
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Commonly used and abused chemicals substances
from plants

• caffeine in coffee
• theophylline in tea
• theobromine in chocolate
• nicotine in tobacco
• cocaine from coca plant leaves
• THC in Cannabis
• and many other narcotic and psychoactive
  substances

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Cooksonia 408 MYA
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Plant Tissue Types

• Meristematic tissue - site of growth in plant
  origin of the other tissue types
• apical meristems - site of primary growth
  lateral meristems - site of secondary growth
• Dermal tissue system - the outer protective
  covering of the plant
• Vascular tissue system - comprises the xylem and
  phloem - it is embedded within the ground tissue
  system xylem forms wood in woody plants
• Ground tissue system - the inner supportive
  tissues of the plant pith in herbaceous plants

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Primary Plant Growth

• Primary growth originates in the apical meristems
  and results in increases in length - tissues
  originating from primary growth make up the
  primary plant body (primary xylem, primary
  phloem, etc) - many vascular plants consist
  entirely of primary tissues

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Secondary Plant Growth

• Secondary growth originates in the lateral
  meristems and results in increases in width -
  there are two lateral meristems
• Vascular cambium which produces secondary
  vascular tissues - secondary xylem to the inside
  and secondary phloem to the outside
• Cork cambium is outside the vascular cambium - it
  forms periderm, which is made of cork tissue -
  the periderm replaces the epidermis as the dermal
  tissue system of the plant

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Xylem tissues

• Secondary xylem is dead at maturity and
  transports water essentially through a hollow
  tube - angiosperms have tracheary cells are
  called vessels and tend to have flattened ends,
  as well as tracheids
• in gymnosperms the tracheary cells are called
  tracheids and usually sharply tapered
• eventually the xylem becomes full of sap and is
  no longer used for water transport, then
  functions in support and forms wood
• Phloem cells are called sieve tube elements
  because of the sieve like plates at the end of
  the cells - they are alive at maturity but are
  crushed as the plant grows in diameter and must
  be continually replaced
• Some sieve cells have companion cells which
  govern transport of material through the sieve

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Xylem Vessels and Tracheids
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Phloem sieve elements
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Garlic Roots
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Fibrous
Tap
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Varieties of Root Systems
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Lateral growth of a willow root