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Ch. 22 seed plants without flowers, "gymnosperms (Division…
Ch. 22 seed plants without flowers, "gymnosperms
Lignophytes
woody plants
Monophyletic groups of woody plants
Spermatophytes
Seed plants
Suites of characteristics
Cycads and their relatives
large compound leaves
radially symmetrical seeds
Manoxylic wood
soft, spongy, parenchymatous
conifers and their relatives
pycnoxylic wood
hard, strong, little parenchyma
small, simple leaves
flattened seeds
Classes of division Spermatophyta
Gymnosperms
ovules located on flat sporophylls
e.g. pine cones
Angiosperms
flowering plants
have carpels
believed to bu tube-like sporophylls
Division Progymnospermophyta: Progymnosperms
Give rise to
gymnosperms
conifers
cycads
other gymnosperms
megaphyllous leaves
vascular cambium
unlimited growth potential
capable of secondary xylem and phloem
Aneurophylates
from shrubs to trees
up to 12 m tall
Archaeopteridales
trees
up to 8.4 m tall
abundant wood and secondary phloem
heterosporous
Evolution of seeds
Chauleria
oldest known pro gymnosperm
390 million years ago
integument
surrounds megasporangium
micropyle
a hole in the integument
allowed sperm to reach the egg
polle chamber
space at top of megasporangium
where microspores collected
Division Pteridospermophyta: seed ferns
First appeared in the Upper Devonian Period
are not all closely related to each other
form a grade rather than a clade
grade
a level of evolution
clade
share a common ancestors
had a long lived vascular cambium
produced xylem and phloem
wood
longer tracheids
manoxylic
Leaves
large
compound
planar
bear seeds
Division Coniferophyta: Conifers
very diverse
trees
moderate to gigantic size
Leaves
Simple needles or scales
often perineal
Simple venation
Pines
Monopodial trees
one main trunk
many branches
wood
exclusively tracheids
still provides annual rings
shoot types
long shoots
tiny papery leaves
in their axil
short shoots
long needle leaves
cones
pollen cones
simple cones
single, short, unbranched axis
bear microsporophylls
seed cones
compound cones
consist of a shoot with auxiliary buds
short axis
bears cone bracts
Pollen
Arrives before the egg is mature
Division Cycadophyta: Cycads
Often confused with ferns or young palm trees
Short plants
less than 1 or 2m tall
trunk
covered with bark
covered with leaf bases
produce seed cones and pollen cones
each on different plants
always dioecious
Approx. 100 species
Smaller Divisions
Division Cycadeoidophyta: Cycadeoids
Almost identical to cycads
subtle differences in stromatal complexes
Division Ginkophyta: Maidenhair tree
single living species
Ginko biloba
Looks like a dicot tree
Has wood similar to conifers
Division Gnetophyta
Contains three groups of enigmatic plants
Mostly vines or small shrubs
Broad leaves similar to dicots
