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vascular plants without seeds, image, image, image, opposite of eachother,…
vascular plants without seeds
The megaphyll line of evolution: euphyllophytes
trimerophytes
several special features:
overtopping
unequal branching
one stem more vigorous
pseudomonopodial branching
main trunk
rather than a series of dichotomies
origin of Megaphylls (Euphylls)
Three distinct types of homoplastic structures called leaves occur in plants
microphylls of zosterophyllophytes and lycophytes
megaphylls-leaves evolved from branch systems
present in all seed plants
ferns
equisetophytes
telome theory
summarizes megaphyll evolution
telomes
last dichotomy
ultimate twigs
planation
subdivisions of lateral branch align in plane
webbing
parenchyma develops between telomes
leaves of gametophytes of nonvascular plants
monilophytes
more than 12,000 species
leptosporangiate ferns
leaf gap
small segment of vascular cylinder
just parenchyma
leaves of ferns may be leathery or delicate
one cell thick
leaves are small (trichomanes)
leaflets
rachis
upper layer of palisade
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lower region of spongy mesophyll
cluster of sporangia
site of meiosis
two types of sporangia
eusporangium
leptosporangia
underside of leaf
cursrent studies suggest
megaphyllous plants
uniteed by 3 synapomorphies
they have megaphylls
30-kilobase inversion DNA
their roots have exarch xylem
monilophytes
lignophytes
woody plants
equisetophytes
division arthrophyta
15 extant species known
scouring rushes
all herbs
no secondary growth
sporanigosphore
horsetails
calamitales
true monopodial growth
early vascular plants
rhyniophytes
earliest fossil record of land plants
Cooksonia a genus of extinct plants
short cylinders
equal dichotomous branching
both branches
cortex of parenchyma
epidermis w/ cuticle
simple bundle of xylem
tracheids
equal size / vigor
simple upright stems
xylem structure of early vascular plants
protostele
no pith
solid mass of xylem
endarch protostele
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metaxylem differentiates on outer edge
protoxylem located in center
exarch protostele
protoxylem on edges
metaxylem located in center
sipphonostele
evolved later
pith is iin center
as occurs in ferns/ seed plants
zosterophyllophytes
small herbs
lateral sporangia
opened transversely along top edge
exarch protostele
no secondary growth
enations
outgrowths
in asteroxylon contained stomata
increased photosynthetic surface area
the microphyll line of evolution: lycophytes
exarch protosteles
may have come from zosterophyllum ancestor
lateral sporangia
morphology
microphylls
enations must have increased photosynthesis
lycophyll has been suggested
micro evolution from small enations
heterospory
cones of strobili
necessary precondition for seed evolution
compact groups of sporangia
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extant genera
lycopodium
fairly common in forests
200 living species
small herbs w/ prostrate rhizomes
short upright branches
tropical regions to arctic
spores germinate bisexual gametophytes
produce:
archegonia
antheridia
selaginella
resurrection plant, S. lepidophylla
heterosporous
ligule
small flap of tissue
concepts
interpolation hypothesis
postulates:
small sporphyte came into existence when zygote germinated mitotically
instead of meiotically
transformation theory
postulates:
after origination of the dibiontic life cycle gametophyte and sporophyte became:
more complex
vascularized
larger
life cycle with alteration of isomorphic generation
dibiontic life cycle
all known fossil plants
multicellular sporangia
multicellular gametophyte
all plants still in existence
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opposite of eachother
protoxylem and metaxylem are swap places
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