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Vascular Plants Without Seeds (Concepts (Transformation theory (After a…
Vascular Plants Without Seeds
Concepts
Dibiontic life cycle
Has a multicellular gametophyte and sporophyte
Monobiontic life cycle
Have only one multicellular generation
Interpolation hypothesis
Small sporophyte came into existence when a zygote germinated mitotically instead of meiotically
Transformation theory
After a dibiontic life cycle originated
Both gametophyte and sporophyte became larger, more complex, and vascularized
Life cycle with alternation of isomorphic generations
Early vascular plants
Rhiniophytes
Equal dichotomous branching
Both branches of equal size and vigor
Vascular land plants
Xylem structure of early vascular plants
Protostele
Solid mass of xylem in the center with no pith
Endarch stele
Protoxylem is located in the center
Exarch protostele
Metaxylem is located in the center
Siphonostele
Pith is present in the center
Zosterophyllophytes
Small herbs without secondary growth
3 distinctions from rhyniophytes
Sporangia are lateral
Sporangia open transversely along top edge
Xylem is an exarch protostele
The microphyll line of evolution: lycophytes
Morphology
Enations are called microphylls
Heterospory
Cones or strobili
Clusters of sporangia
Extant genera
Ligule
Small flap of tissue on the surface of leaves
The megaphyll line of evolution: euphyllophytes
Trimerophytes
Overtopping
Unequal branching
One stem is more vigorous
Pseudomonopodial branching
Single, main trunk rather than a series of dichotomies
Origin of megaphylls (euphylls)
3 synamorphies
Roots have exarch xylem
Have megaphylls
Have a 30-kilobase inversion in the large single-copy region of their plastid DNA
2 sister clades
Monilophytes
Lignophytes
Equisetophytes
Horsetails or scouring rushes
Several genera of extinct plants
Living plants are are all herbs without any secondary growth
Sporangia occur in groups of 5-10 on umbrella-shaped sporangiophore
Monopodial growth
Main trunk
Lateral branches
True leaves
True roots
Ferns
Leptosporangiate ferns
Majority of fern species
Leaf trace
Vascular system of stem is endarch siphonostele
Diverges from the siphonostele
Leaf gap
Small segment of the vascular cylinder as just parenchyma
Eusporangium
Initiated when several surface cells undergo periclinal division
Results in small multilayered plate of cells
Leptosporangia
Initiated when a single surface cell divides periclinally
Forms a small outward protrusion
The term "vascular cryptogams"
Indicates that they have vascular tissue
Because they lack seeds, reproduction is hidden (crypto)
