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Terms in this set (16)
Four Phyla of Gymnosperms
•Pinophyta - aka Coniferphyta includes Pines, firs, spruces, cedars
•Ginkgophyta - Has single living representative, Ginkgo
•Cycadophyta - Leaves superficially palmlike
•Gnetophyta - Three genera
Seven Major Families of Gymnosperms
Pine reproductive cycle
Two kinds of spores produced.
Pollen cones (male strobili) consist of papery or membranous scales.
Microsporangia in pairs toward bases of scales
Meiosis produces microspores that then develop into pollen grains.
Pollen grain consists of four cells and a pair of air sacs.
Air sacs add buoyancy in wind.
Megaspores in megasporangia within ovules.
Pair of ovules at bases of seed cone scales.
Seed cones larger than pollen cones.
Ovule contains a megasporangium containing a nucellus and a single megasporocyte.
Megasporangium surrounded by integument.
Integument has a pore called micropyle.
Megasporocyte undergoes meiosis, producing four megaspores.
Three megaspores degenerate.
Have woody scales with inconspicuous bracts between
- Remaining megaspore develops into female gametophyte with archegonia at micropyle end.
Seed cones take two years to mature.
Pollen grains catch on sticky pollen drops oozing out of micropyle.
Pollen grain produces pollen tube that grows through nucellus.
- Two sperms produced in pollen tube.
- Mature male gametophyte = germinated pollen grain with pollen tube and two sperm
- Sperm have no flagella and no antheridium is formed.
- Megaspore develops.
Female gametophyte and archegonium mature.
Pollen tube arrives at archegonium.
One sperm unites with egg, forming zygote.
Other sperm degenerates.
Embryo nourished by female gametophyte.
Integument becomes seed coat.
Very ancient family with most species extinct
Only 41 species remain all in the southern hemisphere
Single stout trunk with whorled branches
Recognized for formal structure, grow straight and have classic christmas tree shaped
Norfolk island pine
Most diversity in Australasia
Fleshy-coated seeds with large appendage at base
Dominant trees in coniferous forests of Northern Hemisphere
Include world's oldest known living organisms - Bristlecone pines
Up to 5,000 years
Oldest plants on earth, most fire/cold tolerant,
Only one species: Sciadopitys verticillata
evergreen tree bearing whorls of long flexible green cladodes which look like, and perform the function of, leaves but are actually composed of stem tissues
Very expensive family, used in japanese zen gardens
Modified needles look like leaves, known as japanese umbrella pine, living fossil since only one left in family
Bark commonly orange- to red- brown and of stringy texture, often flaking or peeling in vertical strips
Several species have scale-like leaves
Junipers - Seed cones fleshy
Scale leaves overlapping
20 species restricted to east Asia
Spirally arranged evergreen leaves
Commonly called yew
Yew (Taxus) and California nutmeg (Torreya) produce ovules singly at tips of shoots.
Each ovule at least partially surrounded by fleshy, cuplike aril.
Human Relevance of conifers
Edible inner bark and needles of white pine, and seeds of nearly all pines
Masts in sailing vessels
Crates, boxes, matchsticks, furniture
Telephone poles, railroad ties, mine timbers
Turpentine and rosin (both from resin)
Pharmaceuticals (taxol for ovarian cancer from yew trees)
Ginkgo (maidenhair trees)
Only one living species
Only exists in cultivation
Notched, broad, fan-shaped leaves
Leaves on short, slow-growing spurs.
No midrib or prominent veins
Hair-like veins branch dichotomously.
Life cycle similar to pines.
Dioecious- Male and female structures on separate trees.
Seeds enclosed in fleshy seed coat with nauseating odor.
Cycadophyta (the cycads)
Slow-growing plants of tropics and subtropics
Tall unbranched trunks
Crown of large pinnately divided leaves
Life cycle similar to conifers.
Pollination sometimes by beetles.
Has pollen and seed strobili
Cooling leaves since grows in hot areas
NOT pine trees
Produce naked seeds
Phylum Gnetophyta - The Gnetophytes Joint Firs
Unique among the gymnosperms in having vessels in the xylem.
Joint firs (Ephedra) - Shrubby plants of drier regions of southwestern North America
Phylum Gnetophyta Gnetum
Vine-like plants with broad leaves
Phylum Gnetophyta Welwitschia
Only one species, confined to deserts of southwestern Africa
Only two straplike leaves that become tattered and split
Has male and female strobili
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