Please enable JavaScript.
Coggle requires JavaScript to display documents.
"Gymnosperms" - Seed Plants Without Flowers Divisions (2nd…
"Gymnosperms" - Seed Plants Without Flowers Divisions
Definitions and the 1st Division
manoxylic wood - soft, spongy, parenchymatous
pychoxylic wood - hard, strong, little parenchyma
spermatophytes - seed plants
gymnosperms - "naked ovules", flat sporophylls, pine cones
#
1st Division Progymnospermophyta: Progymnosperms
megaphyllous leaves, vascular cambium (secondary xylem, phloem), true woody trees, no seeds
Aneurophytales
vascular cambium
primary xylem was protostele like
shrubs to large trees
webbing between branches, not actually leaves
relictual progymnosperms
Archaeopteridales
abundant wood and secondary phloem
stems had siphonostele - pith surrounded by primary xylem
average height of 8.4m
leaflets = spirally arranged simple leaves
had full megaphylls
lignophytes - monophyletic group of woody plants
angiosperms - flowering plants, carpals become fruits
The 2nd and 4th Divisions
2nd Division Pteridospermophyta: Seed Ferns
wood = trachieds longer and wider, made rows of circular pits
rays were many cells wide and very tall
wood was manoxylic
#
stem had a thick cortex
inner cortex had secretory ducts
stem cells made into parenchyma, not trachieds
vascular cambium with both xylem and phloem
leaves = large, compound, planar
megasporangium = large with bundles of vascular tissue
integument attached at base and was vascularized
woody plant with fern-like foliage that bore seeds instead of sporangia
seeds very large = 11cm long, 6cm diameter
appeared in the Upper Devonian Period
4th Division Cycadophyta: Cycads
trunk has bark and persistent leaf bases
leaves without ovules
less than 1-2m tall
seed cones and pollen cones
each on separate plants, dioecious
pollen cones = spirally microsporangia
pollen tubes and large multifagellated sperm
seed cones - relictual, large, loose pinnately compound megasporophylls
6-8 ovules at base
stout trunks with pinnately compound leaves
tropical, warm weather like Mexico, Cuba, or Australia
thick cortex with secretory ducts around manoxylic wood
rays massive
old stems have only small amount of wood
trachieds long and wide
pith with secretory canals
2nd Division Coniferophyta: Conifers - the largest division
never vines, herbs, or annuals
never have bulbs or rhizomes
giant redwoods of California, 90m tall, 10m diameter
leaves = simple needles or scales
perennial, persisting for many years
1-2 long veins down center of needle-leaf
several parallel veins in scale leaves
leaf veins - endodermis and transfusion tissue
transfusion parenchyma cells and transfusion trachieds
trachieds = cuboidal with circular pits
parenchyma make 3D platform that help transfer materials between vascular and mesophyll tissues
wood = lacks vessels and phloem lacks sieve tube members
very narrow trachieds
pollen and seed cones are woody
#
Pines - monopodial
wood = trachieds. large diameter
rays thin, tall have parenchyma and trachieds
resin canals = vertically in trachieds, horizontal in rays
sticky pitch
no axial parenchyma
phloem = sieve tube members and albuminous cells with tall, narrow rays
cork cambium = thick, good protection from fires
long shoots - tiny papery leaves
short shoots in axis, produce long needle leaves
leaves = thick cuticle, sunken stomata, cylindrical shape
Pollen cones - simple cones
microspore makes small gametophyte with 4 cells
one cells becomes generative
gametophytes shed from tree, a percentage land in seed cones
microspore female undergoes meiosis, makes microspores
FIGURE 22-18
single, short unbranched axis with microsporophylls
Seed Cones - compound cones
short axis = leaves called cone bracts
no sporophylls
each bracts has axillary bud
bud bears megasporophylls
megasporophylls fuse laterally to form ovuliferous scale
have shoot with axillary buds
megasporangium = large mother megaspore undergoes meiosis to form megaspore
retained insde and grows into a large multinucleate megagametophyte
FIGURE 22-24
conifer pollen
pollen tube digests its way towards megagametophyte as egg forms
only 1 zygote develops from the 2-3 eggs fertilized
zygote
1st cells elongate = suspensor that pushes deep into megagametophyte
"other cells" = proembryo, develop into embryo
no double fertilization
The 5th, 6th, and 7th Divisions
5th Division Cycadeoidophyta: Cycadeoids
all extinct
cones had both micro- and megasporophylls
thick, fleshy scales
microsporophylls below mega and curled upward to surround the megasporophyll
megasporangium surrounded by integument with long micropyle
microsporophyll = cup shaped with lots of microsporangia
each ovule had a stalk
FIGURE 22-29
6th Division Gingophyta: Maidenhair Tree
broad leaves with diachotomously branched veins
short and long shoots
wood lacks vessels and axial parenchyma
dioechious and gymnosperms but no cones
#
ovules in pairs a the end of the stalk
large with 3-layered seed coat
single living species - Ginkgo biloba
female trees seeds emit butyric acid = smelly
FIGURE 22-30
7th Division Gnetophyta
Ephedra - tough shrubs and bushes
leaves scale-like
deserts like in Mexico
Welwitschia
short, wide stem
2 perennial leaves only from basal meristem
Africa
Gnetums - vines and shrubs
broad leaves
Asia, Africa, Amazon Basin
Similarities between all 3:
pollen cones are compound and have small bracts
#
seed cones compound with extra tissue surrounding ovules
have vessels in wood
pollen spindle-shaped with narrow ridges
thought to be sister clade to flowering plants
3 groups of engmatic plants: Gnetum, Ephedra, Welwitchia mirabilis