Lab 6

1. Lab 6 Gymnosperms

2. Gymnosperms • seed bearing plants – but naked seeds • often borne on cones • do not produce flowers - angiosperms Gymnosperms -reduced male gametophyte (development of pollen grains) -internal fertilization -reduced female gametophyte (development of ovules) -naked seeds -advanced vascular tissue comprised of tracheids Angiosperms -reduced male gametophyte (development of pollen grains) -internal fertilization -reduced female gametophyte (development of ovules & an embryo sac) -seeds – borne in fruits -development of flowers -advanced vascular tissue with tracheidsand vessels -herbaceous and woody -annuals and perennials

3. Gymnosperms • four gymnosperm phyla: Cycadophyta, Ginkgophyta, Gnetophyta and Coniferophyta • Phylum Cycadophyta – cycads • second largest group of gymnosperms • large cones and palmlike leaves • 130 species survive • Phylum Ginkgophyta - ginkos • only one species left – Ginkgo biloba • deciduous leaves - fanlike formation • tolerates air pollution well • trees bear fleshy seeds that smell rancid • Phylum Gnetophyta – three genera alive today • tropical and desert species • Gnetum – 35 species of tropical trees, shrubs and vines (Africa and Asia) • Welwitschia – one species, Welswitchia (Africa) • Ephedra – 40 species, desert shrubs • produce the compound called ephedrine • Phylum Coniferophyta – largest group • “cone-bearing” • 600 species of conifers • many are large trees • most are evergreens – retain their leaves throughout the year Cycasrevoluta Ginkobiloba Welwitschia mirabilis. Ephedra.

4. Phylum Cycadophyta • found in subtropical and tropical regions • often confused with young palms • stout trunk with compound leaves • most are less than 2m tall • Macrozamia = 18m tall • 9 to 10 genera – ~300 species total • ~25% are considered endangered • take a very long time to grow • stout, cylindrical trunk that does not branch • leaves are pinnate (“feathers” on a bird) are grow directly from the trunk • central leaf stalk with parallel “ribs” emerging from the sides • leaves grow from the top of the crown down Sago palm Cycasrevoluta

5. Phylum Cycadophyta • leaves do not bear ovules • produce seed and pollen cones on separate plants = dioeicious • pollen cones are spirally arranged microsporophylls that bear clusters of microsporangia • pollen grains produce a branched pollen tube and make multiflagellated sperm cells • pollen cone can be very large • seed cones are variable in morphology • they do bear ovules in associated with megasporophylls – variety in number and shapes • require very specific pollinators – usually beetles • seeds contain neurotoxins and should not be eaten Cycasrevolutapollen cone seed cone Cycascircinnalispollen cone Cycascircinnalisseed cone

6. Phylum Gnetophyta • 3 genera of gymnosperms: • 1. Gnetums - are mostly vines or shrubs with very broad leaves • 30 species • native to southeast Asia, tropical Africa and the Amazon basin • seeds are eaten • 2. Ephedra – shrubs and bushes • 40 species • inhabit desert regions in northern Mexico and southwestern US • reduced scale-like leaves • used in the production of ephedrine • 3. Welwitschia– only one species • Welwitschia mirabilis • deserts of South Africa • short stem and only two leaves • leaves grow perennially – becoming increasingly longer • largest leaves in the plant kingdom • unique amongst gymnosperms in that the pollen cone contain small bracts

7. Phylum Gnetophyta Gnetumgnemon– ovules & seeds Gnetumgnemon Gnetumgnemon- male microsporangia

8. Phylum Gnetophyta Ephedra seed cone pollen cone Ephedra sinica Ephedra: ma huang -used in Chinese medicine for 5000 yrs -derived from Ephedra sinica -many Ephedra species used as stimulants -Ephedra plants contain many compounds -most common: ephedrine and pseudo. -ephedrine: sympathomimetic -similar to methamphetamines & epinephrine -increases the activity of norepinephrine on its receptors Ephedra funerea “Mormon tea”

9. Phylum Gnetophyta Welwitschia mirabilis Welwitschia mirabilis - female Welwitschia mirabilis - male

10. Phylum Gingkophyta • contains a single living species – Gingko biloba • also known as the “maidenhair tree” • woody tree – but the wood is very different from conifers and from angiosperm trees • broad leaves – very distinct shape • trees are dioecious • microsporangiate trees • megasporangiate trees • gymnospermous – naked seeds BUT no cones! • ovules occur in pairs at the ends of a short stalk (megasporophyll) – unprotected at maturity • pollen is produced in an organ that is on a stalk and has multiple microsporophylls – each has two microsporangia • when the female tree produces its seeds – contain butyric acid which has a putrid odor Gingko biloba

11. Phylum Gingkophyta ovules megasporophyll Gingko biloba - male Gingko biloba – female microsporophylls, each bearing2 microsporangia

12. Phylum Coniferophyta • 575 species • pine trees, firs, spruces, hemlocks, redwoods, cedars • 290 million years old • largest genus – Pinus • over 100 living species • predominant in the northern hemisphere • also planted in the southern hemisphere – only the Merkus pine occurs there naturally • world’s oldest known living organism – bristle cone pine (4,600 years old)

13. Phylum Coniferophyta: the Conifers Douglas fir. “Doug fir” (Pseudotsuga menziesii) provides more timber than any other North American tree species. Some uses include house framing, plywood, pulpwood for paper, railroad ties, and boxes and crates. LE 30-4ba

14. Pacific yew. The bark of Pacific yew (Taxa brevifolia) is a source of taxol, a compound used to treat women with ovarian cancer. The leaves of a European yew species produce a similar compound, which can be harvested without destroying the plants. Pharmaceutical companies are now refining techniques for synthesizing drugs with taxol-like properties. LE 30-4bb

15. Bristlecone pine. This species (Pinus longaeva), which is found in the White Mountains of California, includes some of the oldest living organisms, reaching ages of more than 4,600 years. One tree (not shown here) is called Methuselah because it may be the world’s oldest living tree. In order to protect the tree, scientists keep its location a secret. LE 30-4bc

16. Sequoia. This giant sequoia (Sequoiadendron giganteum), in California’s Sequoia National Park weighs about 2,500 metric tons, equivalent to about 24 blue whales (the largest animals), or 40,000 people. Giant sequoias are the largest living organisms and also some of the most ancient, with some estimated to be between 1,800 and 2,700 years old. Their cousins, the coast redwoods (Sequoia sempervirens), grow to heights of more than 110 meters (taller than the Statue of Liberty) and are found only in a narrow coastal strip of northern California. LE 30-4bd

17. Common juniper. The “berries” of the common juniper (Juniperus communis), are actually ovule-producing cones consisting of fleshy sporophylls. LE 30-4be

18. Wollemia pine. Survivors of a confer group once known only from fossils, living Wollemia pines (Wollemia nobilis), were discovered in 1994 in a national park only 150 kilometers from Sydney, Australia. The species consists of just 40 known individuals two small groves. The inset photo compares the leaves of this “living fossil” with actual fossils. LE 30-4bf

19. The Conifers

20. Female Pine Cone Cluster of Male Pine Cones Pine needles

22. Pine pollen with wings

23. microsporophyll microsporan- gium microspore (pollen) Female Pine Cone Male Pine Cone

24. Pine pollen cone - microsporophyll & a microsporangium (containing microsporocytes). Microsporangium containing microspores (pollen) Microsporangium With pollen grains microsporophyll Pine pollen with male gametophyte Germinating pine pollen air bladder tube cell generative cell (becomes 2 sperm)

25. mega- spore megasporophyll ovules megasporophyll integument Future ovule bract bract Pine seed cone with ovuliferous scale and developing ovule Developing ovuliferous scale (megasporophyll) in a young pine seed cone female gametophyte Archegonia in pine ovule with egg nucleus 2 Archegonia (developed from the megaspore) within the ovule

26. The genus is divided into two subgenera that are separated by the presence of either one vascular bundle in the leaf (subgenus Strobus) or two (subgenus Pinus). Vascular bundle Vascular bundles Subgenus Strobus with one vascular bundle Subgenus Pinus with two vascular bundles

27. Cross Section of a Pine Leaf