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13 Feb. 2012 Ferns&Moss.ppt 1
FERNS & MOSSES
Seedless plants
13 Feb. 2012 Ferns&Moss.ppt 2
Spore-dispersed 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
13 Feb. 2012 Ferns&Moss.ppt 3
Spore-dispersed 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
13 Feb. 2012 Ferns&Moss.ppt 4
Phylum Pterophyta (Ferns)
13 Feb. 2012 Ferns&Moss.ppt 5
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!
13 Feb. 2012 Ferns&Moss.ppt 6
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)
13 Feb. 2012 Ferns&Moss.ppt 7
Phylum Sphenophyta
13 Feb. 2012 Ferns&Moss.ppt 8
Phylum Lycophyta("club mosses" or "ground pine")
• Short stems with microphylls, – one vein per leaf (veins don’t branch)
• Sporangia at tips of stems or axils of fronds in strobilus
• Heterosporous, two kinds of spores– separate male & female gametophytes.
13 Feb. 2012 Ferns&Moss.ppt 9
Phylum Lycophyta("club mosses" or "ground pine")
13 Feb. 2012 Ferns&Moss.ppt 10
Spore-dispersed 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.
13 Feb. 2012 Ferns&Moss.ppt 11
Phylum Bryophyta(Mosses)
• Familiar, low green soft masses on ground, usually in moist places
13 Feb. 2012 Ferns&Moss.ppt 12
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
13 Feb. 2012 Ferns&Moss.ppt 13
Moss Life Cycle
13 Feb. 2012 Ferns&Moss.ppt 14
Economic uses of ferns, mosses
• Horticulture, landscaping
• Peat moss (Sphagnum)– soil conditioner, holds moisture,– cut, dried, burned as fuel in Ireland,
Scandinavia.
13 Feb. 2012 Ferns&Moss.ppt 15
Formation of a peat bog
• Continental glacier plows up soil• Glacier breaks up as it melts back
13 Feb. 2012 Ferns&Moss.ppt 16
Formation of a peat bog
• Hole left fills with meltwater• Sphagnum grows from edges, may
eventually fill bog
Economic uses of ferns, mosses
• Carboniferous Period (middle Paleozoic)– Ferns, tree ferns, tree-like
"horsetails," tree-like lycophytes fossilized
– Coal deposits
– Power for heavy industry, electrical generation
13 Feb. 2012 Ferns&Moss.ppt 17
13 Feb. 2012 Ferns&Moss.ppt 18
Origins of plants
• from some green algae – multicellular
– same photosynthetic pigments, chlorophyll a, b
– store food as starch
– cellulose cell walls
– alternation of generations
13 Feb. 2012 Ferns&Moss.ppt 19
Evolution of plants
• One group includes mosses– dominant gametophyte
• 2nd group includes ferns, seed plants– Sporophyte dominant
– Vascular tissue
13 Feb. 2012 Ferns&Moss.ppt 20
Evolution of plants• One group includes mosses, hornworts
– dominant gametophyte, non-vascular
• 2nd group includes ferns, seed plants– dominant sporophyte, vascular tissue
13 Feb. 2012 Ferns&Moss.ppt 21
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