Download BIO509 Lecture # 12 File

School of Sciences, Lautoka Campus
BIO509 Botany Lecture 12: Ferns and
Allies Seedless Vascular Plants
Four phyla of seedless vascular plants
• Phylum Psilophyta (whisk ferns).
• Phylum Lycophyta (club mosses and quillworts).
• Phylum Equisetophyta (horsetails and scouring
rushes).
• Phylum Polypodiophyta (ferns)
Learning outcomes
• Know the distinguishing features of seedless vascular plants.
• Know the similarities and differences amongst bryophytes,
seedless vascular plants and higher plants.
• Know the differences between the four phyla of seedless
vascular plants.
• Know the reproductive structures and lifecycle of a fern.
• Understand and appreciate the human and ecological
significance of seedless vascular plants .
Evolutionary trends
As plants move from the aquatic to the terrestrial
environment new features developed:
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Sterile jackets around the gametangia.
Embryos within protective tissues.
Cuticle.
Internal vascular tissue system (xylem and
phloem).
These protect the tissues from drying out
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True leaves
Roots – for absorption and anchorage
Smaller gametophytes
Larger sporophytes
Apical meristem (subapical in bryophytes)
allows branching
– More light interception/ reproductive structures
• Lignin (support)
• Tissue systems (dermal, vascular, ground)
These lower plants do not have seeds
Lets learn some terminologies first
Vascular Tissue System
• Xylem- plant tissue that
conducts water and minerals.
Has Tracheary elements
• Tracheids
• Vessel elements
• Phloem- plant tissue that
conducts food (mainly
sucrose). Has Sieve elements
Vascular Plant Terminology 1
• Leaves- photosynthetic, principal lateral appendages of the stem.
Microphylls - small leaves that contain a single strand of vascular
tissue.
Megaphylls - large leaves that contain multiple strands of vascular
tissue.
Vascular Plant Terminology 2
• Homosporousproduction of one
type of spore from
one kind of
sporangium.
• Heterosporousproduction of two
types of spores
from two different
kinds of sporangia.
Vascular Plant Terminology 3
Sporophyll - a modified leaf that bears sporangia.
Sporangium - a structure that produces spores.
Microsporangium - microspores
Megasporangium - megaspores
Vascular Plant Terminology 4
• Microsporophyll - a modified leaf that bears microsporangia,
a sporangium that produces microspores.
• Megasporophyll - a modified leaf that bears megasporangia,
a sporangium that produces megaspores.
Vascular Plant Terminology 5
• Strobilus- a reproductive structure consisting of
nonphotosynthetic sporophylls; a cone.
– Microstrobilus- a microsporangiate cone.
– Megastrobilus- a megasporangiate cone.
Generalized life cycle of vascular plants
Generalized life cycle of vascular plants
Phylum Psilophyta – The whisk ferns
Phylum Psilophyta – The whisk ferns
• Resemble green whisk brooms.
• Habitat- epiphytic or on rich soils
• Sporophyte has dichotomously
forking stems
• No true leaves or roots
• Rhizoids function as roots
• Grow up to 30 cm
Unique features:
• Stems and sporophytes have neither true leaves or roots
• Stems and rhizomes that fork evenly.
• Enations – green superficial leaf like, vein less photosynthetic
tissues are spirally arranged along the stems.
• Photosynthesis takes place on the stem
• Centrally cylinderal xylem is surrounded by phloem
Psilotophyta are
native to tropical
and sub tropical
regions.
Native to Australia
and the South
Pacific
Reproduction
• Sporangia are at tips of branches.
• Gametophytes are bisexual,
resemble portions of the rhizome
and have a mycorrhizal fungus.
• Homosporous and spores produced
in sporangia (fused into
synangia in Psilotum)
Sporangia
Gametophyte
Psilotum reproduction
Homosporous life cycle
Human and ecological relevance of whisk ferns.
• Little economic importance.
• Spores have oily feel and were used by
Hawaiian men to reduce loincloth skin
irritations.
• Hawaiians also boiled it to make a laxative
liquid.
• It is said that the species Psilotum nudum is one of the very old
plants.
• Psilotum resembles the first land plants that appeared on the
globe about 400 million years ago.
• First land plants had naked stems and terminal sporangia.
Extinct Seedless Vascular Plants
• Representatives (425-370 MYA)
– Rhyniophyta
– Zosterophyllophyta
– Trimerophytophyta
Cooksonia, a vascular plant of the Silurian period. Note tall stature and large
branched sporophyte with numerous sporangia. Psilotum is similar to Cooksonia.
Rhizome (underground horizontal stem)
Questions??