Outline Overview Phylum Pinophyta Phylum Ginkgophyta Phylum Cycadophyta

Outline • • • Overview Phylum Pinophyta Phylum Ginkgophyta Phylum Cycadophyta Phylum Gnetophyta Human Relevance of Gymnosperms v Conifers v Other Gymnosperms

Overview • Gymnosperm refers to the exposed nature of the seeds. v Produced on the surface of sporophylls or similar structures instead of being enclosed within a fruit as in flowering plants. - Female gametophyte is produced inside an ovule that contains a nucellus. Ø Enclosed in integument. v Four living Phyla

Exposed versus Enclosed Seeds

Phylum Pinophyta • The Conifers v Pines - Largest genus of conifers. Ø Over 100 living species. § Include world’s oldest known living organisms (Bristlecone Pines).

Phylum Pinophyta • Structure and Function v Pine leaves are needlelike and are arranged in clusters of bundles of two to five leaves. - Each cluster (fascicle) forms a cylindrical rod if the leaves are held together. v Hypodermis located below the epidermis. v Resin canals develop in mesophyll. - Antiseptic and Insect Deterrent.

Fig. 22. 2

Pine Stem Cross Section

Phylum Pinophyta • Most wood varies considerably in hardness. v Most gymnosperm wood consists primarily of tracheids. - No vessel members or fibers. Ø Soft Wood v Mycorrhizal fungi associated with the roots of most conifers.

Pine Life Cycle

Pine Life Cycle

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Pine Ovule - Longitudinal Section

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Phylum Ginkgophyta • Ginkgo (Maidenhair Trees) v Only one living species. - Notched, broad, fan-shaped leaves. Ø Leaves are produced in a spiral on short, slow-growing spurs. § No midrib or prominent veins. Ø Hair-like veins branch dichotomously. - Life cycle similar to pines. Ø Dioecious

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Phylum Cycadophyta • The Cycads - Appearance of a cross between a tree fern and a palm. Ø Slow-growing plants of the tropics that have tall unbranched trunks. § Crown of largely pinnately divided leaves. - Life Cycle similar to conifers. Ø Pollination is generally brought about by beetles instead of wind.

Fig. 22. 12

Phylum Gnetophyta • The Gnetophytes v Unique among the gymnosperms in having vessels in the xylem. v More than half of the 70 known species are joint firs in the genus Ephedra. v Most of remaining species are in genus Gnetum. - Occur in tropics - Most are vine-like with broad leaves similar to those of flowering plants.

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Phylum Gnetophyta v Third genus, Welwitschia, has only one species. - Confined to temperate deserts of southwestern Africa. Ø Average rainfall only 2. 5 cm. § Plant use CAM photosynthesis. - Only produce two leaves throughout their life span.

Fig. 22. 15

Human Relevance of Gymnosperms • Conifers v Edible Seeds v Crates, Boxes, Matchsticks, Furniture v Telephone Poles v Turpentine and Rosin (Resin) v Fuel (Pitch) v Pulpwood v Ornamentals v Pharmaceuticals (Taxol)

Human Relevance of Gymnosperms • Other Gymnosperms v Ginko Seeds - Food v Ephedra - Mormon tea

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Review • • • Overview Phylum Pinophyta Phylum Ginkgophyta Phylum Cycadophyta Phylum Gnetophyta Human Relevance of Gymnosperms v Conifers v Other Gymnosperms