Seedless Vascular plants

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Seedless Vascular plants

• Chapter 17
• (club mosses, horsetails, ferns, etc.)

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Organization of the Plant body

• The roots make up the root system in which allows
  the plant to absorb its water and minerals
• The stems and leaves make up the shoot system of
  which the stems raise the leaves toward the sun
  for photosynthesis

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Organization Continued

• There are three tissue systems which all occur in
  the organs of the plant
• -Dermal
• -Vascular
• -Ground

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Dermal

• Provides the protective covering of the plant
• Most outer layer
• Vascular
• Consists of two conductive tissues
• -xylem
• -phloem
• Is embedded in the ground tissue system

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Primary and Secondary Growths

• Primary
• Occurs in the tips of roots and stems
• Involves the extension of the roots and stems due
  to the initiation of the apical meristems
• It is the primary plant body that consists of
  primary plant tissues which arise from primary
  growth

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Secondary

• First appeared in the Middle Devonian period
  about 380 million years ago
• It is in addition to primary growth that plants
  undergo secondary growth of which increases the
  thickness of the stems and roots
• The vascular cambium produces secondary vascular
  tissues (secondary xylem and phloem)
• Periderm is formed which then replaces the
  epidermis
• The sec. vascular tissues and the periderm both
  make up the sec. plant body

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Conducting Cells of the Xylem and Phloem

• Tracheary elements
• -conducting cell in xylem
• -have distictive, wall thickenings
• -well preserved in the fossil record
• Sieve elements
• -conducting cell in phloem
• -have soft walls
• -often collapse after they die
• -rarely are well preserved as fossils

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Location of Vascular Tissues

• The vascular tissues are located in the stele of
  the plants
• The stele is the central vascular cylinder made
  up of a central column of ground tissue known as
  the pith

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Location of Vascular Tissues

• Protostele
• - the simplest and most ancient type or
  stele
• -it consists of a solid cylinder of vascular
  tissue in which the phloem either surrounds the
  xylem or is interspersed within it

• Siphonostele
• -a type of stele found in the stems of most
  species of seedless vascular plants
• -is characterized by a central pith
  surrounded by the vascular tissue
• -The phloem can form only the outside

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Roots vs. Leaves

• Roots and leaves evolved in separate ways
• Roots
• -they are relatively simple structures
  that seem to have retained many of the ancient
  structural characteristics which are no longer
  present in the stems of modern plants
• Leaves
• -they are the principle lateral
  appendages of the stem
• -evolutionary there are two different
  distinct kinds of leaves, microphylls and
  megaphylls

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Microphylls and Megaphylls

• Microphylls
• -usually small leaves which contain onle a
  single strand of vascular tissue
• -are typically associated with stems
  possessing protosteles and are characteristic of
  the lycophytes
• Megaphylls
• -usually larger leaves under which with
  few exceptions are associated with stems that
  have either siphonosteles or eusteles

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Reproductive System

• All Vascular plants are oogamous
• -they have large nonmotile eggs and
  small sperm that swim or are conveyed to the egg
• -is favored in plants because only one
  of the kinds of gametes must navigate across a
  hostile environment outside of the plant
• -the sporophyte is ultimately larger and
  structuraly more complex than the gametophyte,
  and free-living

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The Phyla of Seedless Vascular Plants

• Phylum Rhyniophyta
• Phylum Zosterophyllophyta
• Phylum Trimerophytophyta
• Phylem Lycopodiophyta
• Phylum Pteridophyta

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