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Vascular Plants With Seeds (The Megaphyll Line of Evolution:…
Vascular Plants With Seeds
concepts
monobiontic
algae
coleochaete
one multicellular generation
interpolation hypothesis
postulates that a small sporophyte
came into existence when a zygote
germinated mitotically
and not
meiotically
Dibiontic life cycle
#
also known as fossil plants
#
each cell has
multicellular gametophyte
and also multicellular sporophyte
transformation theory
after the dibiontic life cycle originated
both
gametophyte and sporophyte
became
more complex
vascularized
larger
Early Vascular Plants
zosterophyllophytes
small herbs without secondary growth
enations
outgrowths
go from
small
to long thin scales
Equal dichotomous branching
cooksonia
epidermis with
a cuticle
cortex of parenchyma
simple bundle fo xylem
made or tracheids
within annual secondary walls
upright stems
short cylinders
no leaves or naked
rhyniophytes
fossils that have the traits of
homosporous
no separate microspores and megaspores
examples
rhynia
aglaophyton
Xylem Structure of Early Vascular plants
center is a
solid mass of xylem
with no pith
protostele
protxylem is located
in there center
and metaxylem differentiates
on the outer edge of the xylem mass
exarch protostele
metaxylem located
in the center of the xylem mass
protaoxylem
on the edges as several groups
next to the phloem
siphonostele
pith is present in the center
seed plants
with pith in the center
The Microphyll Line of Evolution: Lycophytes
heterospory
many extinct and extant
lycophytes sporangia
clustered together in (these protect them )
cones
strobili
extant genera
ligule
small flap of tissue
on the upper surface of
selaginella leaves
simple structures
are ancient
can be used to distinguish early fossil
selaginellas
from lycopods
morphology
micophylls
envisions in the division
lycophyta
The Megaphyll Line of Evolution: Euphyllophytes
monilophytes
moilophytes
two sister clades
woody plants
lignophytes
euphyllophytes
#
united by three synapomorphies
have megaphylls
30-kilobase inversion
enlarge single copy region
of their plastid DNA
root have exarch xylem
equisetophytes
monopodial growth
a main trunk
lateral branches
true leaves
true roots
consist of several genera
of extinct plants
and one genius
equisetum
with 15 extant species
known as horsetails
sporangia in groups of five
to ten
located on an umbrella shaped
sporangiophore
Origin of megaphylls (euphylls)
subdivisions pf lateral branch become aligned
into one plane
planations
sporophyte
not just leaf
so a leaf like structure
ultimate twigs
those of last dichotomy
are telomes
euphyllophytes
megaphyllous plants from monophyletic clade
telome theory
megaphyll evolution
three distinct types of homoplasic analogous
1 leaves on gametophytes of nonvascular plants
2 enations/micophylls of zosterophyllophytes and lycophytes
3 megaphylls
leaves that evolved from branch systems
are present in all seed plants
ferns
and equsetophytes
Trimerophytes
overtopping
trimerophytes
had unequal branching
one stem was more vigorous
pseudomonopodial branching
pertica
is single main trunk
rather than series of dichotomies
ferns
leaf trace
at each node
it diverges from the siphonostele
leaving small segment of vascular cylinder
as just parenchyma
this is the leaf gap
eusporangia and leptosporangia
eusporangium
initiated when several surface cells
undergo periclinal divisions
resulting in small
multilayered plate of cells
leptosporangia
initiated when a single surface cell
divides periclinally
forms a small outward protrusion
leptosporangiate ferns
ferns familiar to you
