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Chapter 23 Seed Plants 1: Seed Plants Without Flowers (Gymnosperms) -…
Chapter 23 Seed Plants 1: Seed Plants Without Flowers (Gymnosperms)
Concepts
gymnosperms
plants with naked ovules
ovules located on flat sporophylls (pine cones)
spermatophytes
seed plants
lignophytes
monophyletic woody plants
two major suites of characters
manoxylic wood
very soft
parenchymatous wood
large compound leaves
seeds are radially symmetrical
occurs in cycads (and relatives)
pycnoxylic wood
hard
strong wood
small simple leaves
seeds flattened
occurs in conifers (and relatives)
angiosperms
flowering plants
those with carpels are believed to be sporophylls
form tube like closed structure
divisions of seed plants accepted now
gymnosperms
division cycadophyta
coniferophyta
ginkophyta
gnetophyta
angiosperms
division magnoliophyta
Progymnospermophyta
Progymnosperms
3rd group to evolve from trimerophytes
cycads
other gymnosperms
conifers
developed megaphyllous leaves
evolved vascular cambium
secondary xylem/phloem
aneurophytales
relictual progymnosperms
varied in stature
small shrubs
Tetraxylopteris
Protopteridium
large trees
Eospermatopteris
Proteokalon
Triloboxylon
Anuerophyton
archaopteridales
more derived progymnosperm
archaeopteris
trees up to 8.4 m tall
secondary phloem
abundant wood
siphonostele
pith surrounded by primary xylem bundle ring
planted branch systems
spirally arranged simple leaves (leaflets)
heterosporous
microspores 30 micrometers
megaspores 300 micrometers
evolution of seeds
megasporangium
microintegument
tissue layer surrounds megaspore
upward projection
micropyle
hole in integument
pollen chamber
top space of megasporangium
Gnetophyta
enigmatic plants
3 groups
gnetum
vines/small shrubs
broad leaves
Ephedra
about 40 species
tough shrubs/bushes
leaves scale-like and reduced
welwitschia
short wide stem
only 2 leaves
grow from basal meristem (perennially)
get longer continuously
gymnosperms
wood vessels
evolved from tracheids/circular border pits
reproduction
pollen cones
small bracts
compound
seed cones
compound
tissue layers surrounding ovules
Cycadophyta
cycads
most are short
less than 1-2 m tall
bark covers trunk
persistent leaf bases
reproduction
produces both seed cones and pollen cones
dioecious
produced on separate plants
stems
similar to seed ferns
massive rays
long/wide tracheids
thick cortex
small amount of parenchymatous wood
macrozamia
can grow to 18 m tall
Ginkgophyta
single living species
ginkgo biloba
stout trunk
conifer-like wood
many branches
similar to large dicot
reproduction
dioecious
no cones produced
gymnospermous
ovules produced in pairs
lacks axial parenchyma
lacks vessels
broad leaves
dichotomously branched veins
short/long shoots
Cycadeoidophyta
all are extinct
vegetative features
close to cyads
reproduction
cones contain
microsporophylls
megasporophylls
Pteridospermophyta
seed ferns
cyadophytes
three divisions
pteridospermophyta (all extinct)
Devonian period
cycadophyta (extant)
cycadeoidophyta (all extinct)
Coniferophyta
very diverse
550 species
moderate to gigantic size
simple or scale leaves
leaves perennial
one or two veins in leaf
has endodermis
transfusion parenchyma
transfusion tissue
transfusion tracheids
pines
monopodial
main trunk with many branches
wood exclusively has tracheids
large diameter (spring)
narrow diameter (summer)
annual rings
summer wood
spring wood
rays
thin
tall
ray parenchyma
ray tracheids
resin canals
thick sticky pitch
runs vertically along tracheids
horizontal in rays
phloem
sieve cells
narrow tall rays
albuminous cells
cork cambium
thick tough bark
two types of shoot
long
tiny papery leaves
short
long needle leaves
xeromorphic characters
stomata sinking
cylinder shape
cuticle is thick
two types of cones
pollen
simple cones
unbranched axis (single/short)
bears microsporophylls
seed
complex
compound cones
microscopic axillary buds
shoot
cone bracts
short axis leaves
each bract has axillary bud
ovuliferous scale
