FERNS

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FERNS MOSSES

• Seedless plants

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Seedless plants

• Seedless, dispersion by spores
• Advantages of spores
• Cheap, each one small, requires small resource
  investment
• Produced in huge numbers
• Can result in huge numbers of offspring
• Disadvantage
• Wasteful, most spores unsuccessful
• Must land on good moist soil
• Little resource to support growing gametophyte

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Seedless vascular plants

• Vascular tissues, xylem, phloem
• Allow growth to large size
• Local ferns, horsetails, club mosses not very
  large, fronds 30-40 cm
• Tree ferns (tropical) to 18 m tall w/ fronds 3 m
  long
• Prehistoric club mosses tree-sized

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Phylum Pterophyta (Ferns)
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Phylum Pterophyta (Ferns)

• Leafy fronds, usually compound
• Fronds grow as fiddleheads
• Sporangia in sori under fronds
• One kind of spores only
• homosporous
• Gametophyte with both antheridia archegonia
• Antheridia release sperm before archegonia mature!

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Phylum Sphenophyta("horsetails" or "scouring
rushes")

• Hollow, segmented stems
• Minute bristle-like gray-brown fronds
• Sporangia at tips of stems in strobilus
• Heterosporous, two kinds of spores
• separate male female gametophytes.
• Stems hard, gritty with crystals of silica (SiO2,
  sand, glass)

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Phylum Sphenophyta
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Phylum Lycophyta("club mosses" or "ground pine")

• Short stems with microphylls,
• one vein per leaf (veins dont branch)
• Sporangia at tips of stems or axils of fronds in
  strobilus
• Heterosporous, two kinds of spores
• separate male female gametophytes.

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Phylum Lycophyta("club mosses" or "ground pine")
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Seedless nonvascular plants

• Lack xylem or phloem
• Limited ability to transport water, minerals,
  sugars
• Usually live in moist places
• Some can endure drying, metabolism ceases until
  they are wet again.

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Phylum Bryophyta(Mosses)

• Familiar, low green soft masses on ground,
  usually in moist places

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Phylum Bryophyta(Mosses)

• Life Cycle (very different from ferns, etc.)
• dominant GAMETOPHYTE (haploid)
• familiar form
• green, with tiny leaf-like blades,
• antheridia archegonia at top of moss
• zygote grows into SPOROPHYTE (diploid)
• stalk capsule
• Capsule dries, splits open, releases spores
• Spores grow into GAMETOPHYTE

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Moss Life Cycle
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Economic uses of ferns, mosses

• Horticulture, landscaping
• Peat moss (Sphagnum)
• soil conditioner, holds moisture,
• cut, dried, burned as fuel in Ireland,
  Scandinavia.

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Formation of a peat bog

• Continental glacier plows up soil
• Glacier breaks up as it melts back

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Formation of a peat bog

• Hole left fills with meltwater
• Sphagnum grows from edges, may eventually fill bog

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Economic uses of ferns, mosses

• Ferns, tree ferns, tree-like "horsetails,"
  tree-like lycophytes in Carboniferous Period
  (mid-Paleozoic)
• Coal deposits
• Power for heavy industry, electrical generation

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Origins of plants

• from some green algae
• multicellular
• same photosynthetic pigments, chlorophyll a, b
• store food as starch
• cellulose cell walls
• alternation of generations

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Evolution of plants

• One group includes mosses
• dominant gametophyte
• 2nd group includes ferns, seed plants
• Sporophyte dominant
• Vascular tissue

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Evolution of plants

• One group includes mosses
• dominant gametophyte
• 2nd group includes ferns, seed plants
• dominant sporophyte, vascular tissue

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Challenges to terrestrial organisms ( how
plants meet the challenges)

• 1. Getting water, water transport to cells
• specialized vascular tissues
• 2. Evaporation, drying
• waxes, oils in "epidermis," close stomata
• 3. Gravity, need for support
• fluid pressure in vascular tissue
• lignified xylem wood
• 4. Rapid temperature changes
• evaporative cooling requires even more water!
• seasonal drop leaves or close stomata