Post on 03-Dec-2014
Chapter 4: Evolution and Diversity of Vascular Plants
Michael G. Simpson
Vascular Plants = Tracheophyta (Tracheophytes)
Apomorphies?
Alternation of Generations: Haploid (n) & Diploid (2n) adult phases
“Bryophytes”: Gametophyte dominant, long-lived
Bryophytes (Liverworts, Hornworts, Mosses): Gametophytes are dominant, long-lived
Alternation of Generations: Haploid (n) & Diploid (2n) adult phases
Vascular Plants: Sporophyte dominant, long-lived
Vascular Plants: Sporophytes are dominant
Rhynia
Sporophytic axes branched with
multiple sporangia
Two early branching patterns in vascular plants:
lignin - hard substance secreted within secondary cell wall
Major adaptive:added structural support enabled
vascular plants to grow much larger.
secondary cell wall
- forms between 1˚ cell wall and plasma membrane in some plant cells
- adds structural support
- found in tracheids, vessels, fibers (all dead cells)
lignified secondary cell wall
Sclerenchyma
1) Secondary cell wall (+ primary)
2) Dead at maturity (usually)
Fibers
Elongate, sharply tapering
Sclerenchyma
1) Secondary cell wall (+ primary)
2) Dead at maturity (usually)
Sclereids
Isodiametric to irregular
Tracheary elements1) cells that function in water/mineral conduction2) cells dead at maturity, with lignified, 2˚ cell walls3) cells arranged end-to-end, forming long tubes
Xylem = tissue composed of:
1)tracheary elements
2)parenchyma
3)fibers
(These have common origin/location/function.)
Tracheary ElementsTracheids – imperforate (only pits at end walls). Found in
most monilophytes (except Equisetum and some lepto. ferns) and most gymnosperms (except Gnetales)
Vessels – perforation plates = holes in end walls. Evolved independently from preexisting tracheids in Equisetum, a few leptosporangiate ferns, all Gnetales, and almost all angiosperms
Sieve Elements
Sieve cells – only sieve areas Sieve tube members - Sieve plates
All vasc. pls. except angiosperms Apomorphy of Angiosperms
-cells with sieve areas/plates, having pores lined by callose
callose (polysaccharide composed of β-1,3-glucose units) -lines pores of sieve areas!
Phloem
= tissue composed of:
1)sieve elements
2)parenchyma
3)fibers
These have common origin/function.
Casparian Strip: forces fluids from outside through plasma membrane = selective absorption
Endodermis – single layer of cells surrounding vasculature of roots and some underground stems.
Rhynia- one of earliest
vascular plants(ca. 400 million years
ago)
- lacked roots
Roots
Function in anchoring and absorption.
Root
apical meristem- region of actively
dividing cells
RootsFive diagnostic features:
1) Root cap – functions to protect apical meristem and lubricate root during growth.
2) Root hairs – function to greatly increase water/mineral absorption (exception Psilotopsida).
3) Central vascular cylinder – site of conduction of water/minerals and sugars.
4) Endodermis – Casparian strip functions in selective absorption.
5) Endogenous lateral roots – develop from pericycle or endodermis, penetrate to outside.
Mycorrhizae
Symbiotic association with various species of fungi.
Found in many, if not most, vascular plants.
Fungus aids plant by
1) increasing surface area for water and mineral absorption
2) increasing efficiency of mineral absorption.
Fungus benefits in obtaining photosynthates (sugars and other nutrients) from the plant.
Tracheophyta – Classification
Lycopodiophyta – lycophytes
Apomorphies: 1)Roots dichopodial
-apical meristem may branch into two.
2) Root protoxylem endarch (to inside)
Protoxylem – first xylem formedMetaxylem – later xylem
3) Stem protoxylem exarch (to outside)
4) Sporangia dorsiventral (flattened upper and lower surfaces)
with transverse dehiscence.
Shoot = stem + leaves
Leaf – sporophytic
Lycophyll – simple leaf with 1 vein, no leaf gaps.
Tracheophyta – Classification
LYCOPODIOPSIDA
Lycopodiaceae
homosporous = 1 type of spore
5 genera: Huperzia, Lycopodiella, Lycopodium,
Pseudolycopodiella, Phylloglossum)
Lycopodium digitatum
Ligule – tiny appendages on upper side of leaf (near base)
ISOETOPSIDA
Selaginellaceae + Isoetaceae
1) Leaves ligulate
2) Heterosporous – 2 types of spores
Heterospory – two types of spores:
megaspores (from megasporangia)
microspores (from microsporangia)
Isoetes – quillwort/Merlin’s grass
Isoetaceae
Quillwort family
1 genus:
Isoetes (ca. 200 spp.)
Lycopods native to San Diego area:
Isoetes Merlin’s Grass
Isoetes orcuttii
Isoetes howellii
Selaginella
spike-moss
Selaginellaceae
Spike-moss family
1 genus:
Sellaginella (700 spp.)
Selaginella bigelovii
Selaginella cinerascens
Some Selaginella
have dimorphic
leaves
Selaginella apoda
2 rows large leaves
Selaginella apoda
2 rows small leaves
Some Selaginella
have dimorphic
leaves
Lepidodendron
Extinct Lycopods were tall trees:
make up some of coal deposits
Euphyllophyta
Apomorphies:1) roots monopodial2) root protoxylem exarch3) sporangia terminal on lateral branches, longitudinally dehiscent
Archeopteris
Euphyllophyta
Apomorphies:1) roots monopodial2) root protoxylem exarch3) sporangia terminal on lateral branches, longitudinally dehiscent4) shoot with euphylls
shoot = stem + leaves
Euphyllophyta
Apomorphies:1) roots monopodial2) root protoxylem exarch3) sporangia terminal on lateral branches, longitudinally dehiscent4) shoot with euphylls
Leaves of euphyllophytes:a)evolved by planation & webbing of stemsb)have multiple veinsc)have a leaf gap – parenchyma replaces vascular tissue upper junction of leaf trace with stem vasculature
Euphyllophyta
Apomorphies:1) roots monopodial2) root protoxylem exarch3) sporangia terminal on lateral branches, longitudinally dehiscent4) shoot with euphylls5) 30 kb chloroplast DNA inversion
Tracheophyta – Classification
Monilophyta-monilophytes
Apomorphies:1) stem protoxylem mesarch2) siphonostele
Equisetopsida(Equisetophytes)
EquisetaceaeEquisetum
Horsetails / Scouring Rushes
Equisetopsida
Apomorphies:1) stem ribbed with canals2) leaves reduced, whorled
Equisetopsida
Apomorphies:1) stem ribbed with canals2) leaves reduced, whorled3) sporangiophore4) spores with elaters, chlorophyllous
Equisetum hyemale common scouring-rush Equisetum laevigatum smooth scouring-rush
whorled microphylls
cone(strobilus)
Subgenus Hippochaete – souring-rushes
Equisetum arvense Common Horsetail
Subgenus Equisetum – horsetails
Calamites
-fossil (extinct) equisetophyte,
was tree-sized, makes up coal deposits today
Psilotopsida
Apomorphies:1) Roots unbranched, root hairs absent.2) Gametophyte subterranean, mycorrhizal.
Psilotopsida
Two members:
1) Ophioglossales ophioglossoid ferns
2) Psilotales whisk ferns
Ophioglossales:
One family: Ophioglossaceae
4 genera, incl. Botrychium, Ophioglossum
Ophioglossaceae
Ophioglossum californicum Calif. Adder’s Tongue
Psilotales
Apomorphies:
1) Roots lost.
2) Leaves reduced (microphylls or enations).
3) Synangium with bifid appendage.
Psilotales
One family:
Psilotaceae
2 genera:
Psilotum
Tmesipteris
Psilotum nudum
dichotomous branching
enations / microphylls
Psilotum nudum
Psilotum nudum
synangium
bifid(2-forked)appendage
Marattiopsida
Marattioid Ferns
Apomorphy:
1) Polycyclicsiphonostele
Marattiaceae
eusporangia
PolypodiopsidaLeptosporangiate Ferns
Apomorphy:Leptosporangium
PolypodiopsidaLeptosporangium:
- one cell thick
- spores ejected
Stem:
rhizome
trunk
vine
fern leaves can have specialized terminology:
leaf = frond
petiole = stipe
major divisions = pinna (1˚, 2˚, etc.)
ultimate divisions = pinnules
fern leaf venation:
open (simple or forked), reticulate
fern scales:
e.g., clathrate or non-clathrate
sorus (pl. sori) – aggregation of sporangia
indusium - flap
shape /
morphology
leptosporangium / annulus
-varies with different groups/families
egg
sperm
Fern leaf development: circinate
fiddle head - crozier
Salviniales
Apomorphies:1) aquatic adaptation
2) heterospory (independently evolved)
3) sporocarps (dormant, seed-like body, house specialized sporangia)
Two famlies:Marsileaceae – clover fern family
Salviniaceae – floating fern family
Marsilea Salvinia Azolla
Marsileaceae
Marsilea
Pilularia
Salviniaceae
Azolla
Salvinia
Azolla Mosquito Fern
- symbiotic relationship with blue green bacteria; “seeded” in rice paddies for nitrogen fixation
- inhibits mosquito population by covering surface
- fodder for animals
Cyatheales:
Cyatheaceae
largest family of tree ferns
(trunk arborescent)
Cyathium
a tree fern
Aspleniaceae
-linear sori / indusia
Polypodiales:
A few families:
Polypodiaceae
- sori exindusiate (“naked)
Polypodium californicum California Polypody
Polypodiaceae:sorus
exindusiate
Platycerium Staghorn Fern
sporangia “acrostichoid” (not aggregated
into sori)
Polypodiaceae
Pteridaceae
-false indusium
Cyathium
a tree fern
Adiantum reniformis
California Maidenhair FernPteridaceae