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Chapter 21 - Vascular Plants Without Seeds (The Megaphyll Line of…
Chapter 21 - Vascular Plants Without Seeds
Early Vascular Plants
life cycles
monobiotic = one multicellular generation
interpolation hypothesis = sporophyte from mitotic division
dibiontic life cycle = two multicellular generation
Rhyniophytes
examples
Rhynia
Cooksonia
Aglaphyton
Xylem Structure of Early Vascular Plants
endarch protostele
protoxylem = center
metaxylem = outer edge
exarch protostele
metaxylem = center
protoxylem = outer edge
protostele = no pith center is xylem
siphonostele
pith occurs in center
example: seed plants
Equal dichotomous branching =branches of equal size
Zosterophyllophytes
small herbs
no secondary growth
enations = outgrowths
The Microphyll Line of Evolution: Lycophytes
Heterospory
ancient line that evolves separate from seed plants
similarities between seed plants and lycophytes
protection
cones
strobili
Extant Genera
spirally arranged an their stems
no secondary growth
lycopodium is very common
spores
selaginellas
ligule on upper surface of leaf
flap of tissue = ligule
CAM photosynthesis
Morphology
micro = evolution from small enations
evolved true roots
microphyll is the older term
fossils only 10cm of wood
The Megaphyll Line of Evolution: Euphyllophytes
#
Trimerophytes
psuedomonopodial branching = single trunk
overtopping = one stem is more vigorous
more regular and controlled branches
Lower Devonian ---> Upper Devonian
Origin of Megaphylls
#
leaves evolved from branch systems
telome theory
megaphyll evolution
telomes = ultimate twigs of past generation
planation = one plane
euphyllophytes
webbing = parenchyma
sporophyll = sporangium bearing leaf like
Monilophytes
have megaphylls
30 kb inversion in plastid DNA
roots have exarch xylem
two sister clades
lignophytes
monilophytes
Equisetophytes
horsetails or scouring rushes
whorl of fused leaves at the nodes
division Arthrophyta
sporangiophore = umbrella shaped
characteristics
#
main trunk
lateral branches
monopodial growth
true leaves
true roots
Ferns
Eusporangia and Leptosporangia
lepto. = small outward protrusion
eu. = multilayered
several cells undergo division
Psilotum and Tmesipteris
highly derived
prostrate rhizomes
simplest of living vascular plants
characteristics
leaf gap = small segment of parenchyma left
leaf trace = at each node
sori = cluster of sporangia for meiosis
mostly homosporous
The Term "Vascular Cryptogams"
#
ferns and fern allies
reproduction is hidden
all the plants in this chapter
lack: seeds, flowers, fruits
have vascular tissue
