Transcript BIO509 Lecture # 14 File

School of Sciences, Lautoka Campus
BIO509 Botany Lecture 14: Phylum
Polypodiophyta (ferns)
Phylum Polypodiophyta (ferns)
• Some 11,000 species.
– largest group of plants beside flowering plants.
• Relatively abundant in fossil record.
• Most diverse & most abundant in the tropics.
– About 30% of tropical ferns are epiphytic.
• No secondary growth (wood formation).
• Have megaphylls (system of veins – venation) commonly
referred to as fronds.
• Most ferns are homosporus.
• Water ferns are the only heterosporous living ferns.
• Require water for sexual reproduction.
• Various forms from tiny floating forms to giant tree ferns.
Some ferns of Fiji
Tree ferns (balabala)
Cyathea lunulata
• To 24m high and
stems to 30cm in
diameter.
• Thickening of stem is
accomplished by
deposition of fibrous
root material.
Botrychium
• Herbaceous
• 1 sp. in Fiji
(Nadarivatu)
• Only living fern genus
with vascular cambium
(produces secondary
growth- wood)
Bird’s nest fern
Asplenium nidus
• Epiphytic.
• Debris collects
in the nest
and gradually
turns into
humus.
Pyrrosia
Epiphytic ferns.
Rhizomes are
exposed to air.
Basket fern
Drynaria rigidula
Form a basket to catch the
rain and falling detritus from
higher up in the rainforest
canopy from which fertile
fronds grow.
Vegetable fern – Ota
Diplanzium proliferum
• Most commonly
consumed fern
Golden leather fern
Acrostichum aureum
Common species in brackish
swamps throughout Fiji.
Thick leathery leaves.
Young fronds are edible when
boiled.
Floating ferns
Salvinia
Water fern
Leaves in whorls of 3: two float
and are covered by hairs, other
hangs down, divided so looks
root-like and bears sporangia.
Heterosporus
Salvinia auriculata: introduced
to Fiji for aquaria, has escaped
and is now established along
rivers.
Water fern
Marsilea
Leaves like clover
Slender rhizomes
Grow in mud / damp soil,
often with leaves floating on
water surface.
Produce drought-resistant
sporocarps (bean-shaped
reproductive structures)
Germinate in water to
produce megasporangia and
microsporangia
Fern Reproduction
• The sporophyte is the dominant or conspicuous phase of the
life cycle.
• Sporophyte consist of fronds, rhizome (stem), adventitious
roots and ‘fiddleheads’.
• Blades are divided into segments called pinnae (singular:
pinna) that are attached to a midrib or rachis.
• When blades mature, small circular rust-colored patches
(clusters) appear on the lower surface.
• These are sporangia. These clusters are called sori (singular:
sorus)
• Fronds first tightly coiled
(fiddleheads)
– leaf development known as
circinate vernation
• Uncoil due to differential growth
on top and bottom.
Expanded mature fronds
have small circular rust
colored sporangia.
Sporangia occur in
numerous clusters called
sori (singular sorus).
Sori are protected by
indusia (singular –
indusium).
Microscopic sporangia are surrounded
by a row of brownish cells which look
like tiny millipede called the annulus.
Annulus helps in dispersing the spores.
• Under the influence of moisture,
catapults spores out.
Gametophytes
• Spores germinate in moist
habitats
• Grow into gametophyte
(prothallus; 5-6 mm)
• Antheridia produce flagellated
sperm.
• Fertilization occur on
archaegonia
• Single zygote forms
• Grows into sporophyte
• Gametophyte disintegrates.
Human and Ecological Relevance of Ferns
• Ferns make ideal house plants (require low
light, not susceptible to pests)
• Ferns act as air filters removing air pollutants
• Tree ferns provide good shade for anthuriums.
• Ferns are eaten in many parts of the world.
• Has been used in folk medicine.
• Fronds can be used for thatching houses.
Questions??