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Vascular Plants Without Seed Screen Shot 2020-11-10 at 11.55.17 PM,…
Vascular Plants Without Seed Screen Shot 2020-11-10 at 11.55.17 PM
Early Vascular Plants
-Rhyniophytes
earliest fossils
belong to
Cooksonia
genus of extinct plants
upright stem
simple
short cylinder
no leaves
equal dichotomous branching
plants of Cooksonia
had epidermis
with a cuticle
a cortex of
parenchyma
homosporous
ends of branches
swollen
large multicellular masses
sporogenous
Fossils
#
other rhyniophytes
Rhynia
Aglophyton
Xylem Structure of Early Vascular Plants
prostostele
2 types
exarch protostele
prtoxylem
edges
next to phloem
metaxylem
center
endarch protostele
protoxylem
center
metaxylem
differentiates after
cells have expanded
solid mass of xylem
no pith
siphonostele
pith
centre
Zosterophyllophytes
named after
principal genus
Zosterophyllum
no secondary growth
characteristics
lateral sporangia
sporangia opened transversely
exarch protostele xylem
small bunches
The Microphyll Line of Evolution: Lycophytes
Heterospory
cones/stroboli
protects
have
microspores
microgametophytes
megaspores
megagametophytes
necessary precondition
for
evolution of seeds
Extant Genera
Morphology
earliest lycophytes
members of genera
#
Drepanophycus
Baragwanathia
large enations
up to 4cm
microphyll
contained a single
well-developed trace of
vascular tissue
evolution of roots
important advance
anchor firmly
absorb efficiency
grow to tremendous size
The Megaphyll Line of Evolution: Euphyllophytes
Monilophytes
#
megaphyllous plants(euphyllophytes)
united by
3 synapomorphies
they have megaphylls
they have a 30-kilobase inversion in the
large single-copy region of their plastid DNA
their roots have exarch xylem
the clade
containing fern
Equisetophytes
classified as
division Arthrophyta
consists
several genera of
extinct plants
and
one genus, Equisetum
15 extant species
known as
horsetails or scouring rushes
reproductive structure
specialized
sporangiophore
sporangia occurs
umbrella-shaped
arranged in
compact spirals
strobilus
monopodial growth
Origin of Megaphylls (Euphylls)
megaphylls
evolved from
branch system
present in
all seed plants
telome theory
megaphyll evolution
sporophyll
leaf-like structure
sporangium bearing
euphyllophytes
Ferns
leptosporangiate ferns
can be found
almost in
any habitat
prennial
herbaceous
leaf trace
at each node
leaf gap
small segment of
vascular cylinder
leaves
leathery or delicate
2 types of sporangia
Eusporangia
initiated when
several surface cells undergo
periclinal divisions
small multilayered plate of cells
Leptosporangia
initiated when
single surface cell
divides periclinally
a small outward protrusion
2 small genera
Psilotum
occurs in
tropical and subtropical region
highly derived
highly simplified
only species
whose gametophytes
contain
vascular tissue
Tmesipteris
limited to
Australasia
Trimerophytes
proposed in 1968
for 3 genera of extinct plants
Psilophyton
Pertica
Trimerophyton
overtopping
most imp trend
pseudomonopodial branching
displayed by pertica
branches
lateral
The Term “Vascular Cryptogams”
the name indicates
they have
vascular tissue
fern/fern allies
lack seeds
hidden reproduction system
crypto
shared ancestral features
symplesiomorphies
Concepts
all extant plants
have a
dibiontic life cycle
monobiontic
interpolation hypothesis
postulates
small sporophyte came into existence
when a zygote germinated
mitotically
transformation theory
postulates
after the dibiontic life cycle originated
both gametophyte and sporophyte
became larger,
more complex
vacsularize4d
Fossils that have these general
characters are called rhyniophytes.
similar(presumed ancestor)
Many monilophytes are plants we know as ferns
