Please enable JavaScript.
Coggle requires JavaScript to display documents.
Ch 21:Vascular Plants Without Seeds (The Megaphyll Line of Evolution:…
Ch 21:Vascular Plants Without Seeds
Early Vascular Plants
Rhyniophytes
Xylem Structures of Early Vascular Plants
two types organization
protostele
endarch protostele
center soild mass w/no pith
protoxylem is located in the center
metaxylem differentiates on the outer edge of xylem mass
exarch protostele
metaxylem located in center of xylem mass
protoxylem on edges as several groups next to phloem
evolved later
siphonostele
pith is in center
as in stems of ferns and seed plants
earliest fossils that vascular land plants
Cooksonia
extinct
upright simple stems
no leaves
naked stems
equal dichotomous branching
branches equal size and vigor
ends swollen and contained sporogenous tissue
epidermis w/cuticle
cortex with parenchyma
simple bundle of xylem w/tracheids w/annular secondary walls
homosporous
no separate micro and megaspores
Rhynia and Aglaophyton
similar to Cooksonia
prostrate rhizome
upright naked stems
terminal sporangia
stomata and guard cells in epidermis and layer of cuticle
Horneophyton
sporophytes w/naked axes branched dichotomously
20cm tall
stomata and terminal sporangia
short columella
stem base swollen
Zosterophyllophytes
Zosterophyllum
small herbs w/out secondary growth
features similar to rhyniophytes
three characteristics distinct group
sporangia lateral
sporangia opened transversely along top edge
xylem was an exarch protostele
grow in small bunches
lower portions stem no cuticle
stems naked
branched dichotomously
small amount xylem w/tracheids
w/annular and scalariform secondary walls
some small enations
The Microphyll Line of Evolution: Lycophytes
Morphology
Drepanophycus and Baragwanathia
large enations
outgrowths
scales
single well developed trace of vascular tissue
increased photosynthesis
called microphylls
roots
anchor firmly
absorb efficiently
allow to grow to tremendous size
convergent evolution
Heterospory
extinct and extant lycophytes sporangia clustered as compact groups
cones/strobili
protection
microspores and megaspores
germinated giving rise to distinct mega and microgametophytes
megaspore developed into megagametophyte w/out enlarging
necessary for evolution of seeds
Extant Genera
Lycopodium
ground pine or club moss
common in forests
tropical to artic
small herbs
w/prostrate rhizomes that have true roots
short upright branches
microphylls spirally arranged on stems
secondary growth never occurs
sporangia in cones or along roots
homosporous
spores grow into bisexual gametophytes
antheridia
archegonia
Selaginella
less common in temperate N America
smaller plants
overlooked to be mosses
S. lepidophylla
curls up and turns brown
uncurls
turns green when remoistened
amorphic condition of being heterosporous
megagametophyte develops inside megaspore wall
small flap tissue
ligule
upper face of leaves
Isoetes
genus of 60 species
small unusual plants
quillworts
grow in wt muddy areas, occasionally dry
body
small corm like stem
roots attached below and leaves above
heterosporous
almost every leaf contains sporangia
microphylls have ligules
The Megaphyll Line of Evolution: Euphyllophytes
Trimerophytes
three extinct plants
Trimerophyton
distinct advancement of rhyniophytes
overtoping
unequal branching, one stem more vigorous
Psilophyton
Pertica
pseudomonopodial branching
single main trunk
small lateral branches
some fertile
some sterile
Origin of Megaphylls (Euphylls)
homoplastic (analogous) structures
leaves on gamtophytes of nonvascular plants
enations/microphylls of zostrophyllophytes and lycophytes
megaphylls, leaves that formed from branched stems
in all seed plants, ferns, and equisetophytes
telome theory
ultimate twigs
subdivisions of a lateral branch become aligned in one plane
planation
webbing
parenchyma develops between telomes and lower branching
monophyletic clade
Monilophytes
united by three synapmorphies
roots have exarch xylem
megaphylls
30 kilobase inversion in single copy region of plasid DNA
two sister clades
monilophytes
ferns
Leptosprangiatae
Marattiales
Ophioglossales
fern allies
equisetophytes
horsetails
Psilotales
ferns
lignophyts
woody plants
Equisetophytes
division Arthrophyta
several genera of extinct plants and one genus Equisteum
15 extant specis
horsetails
scoring rushes
herbs w/out secondary growth
aerial stems
jointed structure
worls of fused leaves at nodes
leaves
small
single trace of vascular tissue
small megaphylls
branches
alternate w/leaves
have piths
siphonosteles
protoxylem forms next to pith
endarch
true roots present
reproductive structures
specialized sporangia
occur in groups of 5-10
located on umbrella shaped sporangiophore
Ferns
Eusporangia and Leptosporangia
Eusporangium
initiated when several surface cells undergo periclinal divisions
resulting in small multilayered plate of cells
outer cells develop into the sporangium wall
inner cells proliferate into sporogenous tissue
results in relatively large sporangium w/many spores
Leptosporangia
initiated when single surface cell divides periclinally and forms a small outward protrusion
undrgoes several more divisions
result in small set of sporogenous cells and thin layer sterile cells
Psilotum and Tmesipteris
simplest of all living vascular plants
Psilotum
small plants w/prostrate rhizomes
upright stems
branch dichotomously
have epidermis, cortex, simple vascular cylinder
lost capacity to make roots and leaves
gametophytes
short unbranched cylinders
less than 2 mm in diameter
surface covered in rhizoids
hetrotrophic
contain vascular tissue
tropical/subtropical regions
can live in most habitats
sporophyte
consists of a single axis
vertical rhizome
horizontal rhizome
bear true roots and megaphyllous leaves
vascular system of stem is endarch siphonostele
node
leaf trace diverges from siphonstele
small segment of vascular cylinder region left
leaf gap
leaves leathery or delicate
one cell thick in firmly ferns
many layers thick in most
upper layer palisade, lower spongy mesophyll
small or up to 7 meters long
compound w/rachis and leaflets
most homosporous
two groups water ferns heterosporous
Marsileacea
Salviniaceae
The Term "Vascular Cryptogams"
ferns and fern allies
vascular tissue
lack seeds, flowers, fruit
reproduction hidden = crypto
cladograms based off of shared dervived features
synapomorphies
