Introduction to Seed Plants: Gymnosperms

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

Overview Gymnosperm refers to the exposed nature of the seeds.  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.  Enclosed in integument.  Four living Phyla

Exposed versus Enclosed Seeds

Phylum Pinophyta The Conifers  Pines - Largest genus of conifers.  Over 100 living species.  Include world’s oldest known living organisms (Bristlecone Pines).

Phylum Pinophyta Structure and Function  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.  Hypodermis located below the epidermis.  Resin canals develop in mesophyll. - Antiseptic and Insect Deterrent.

Pine Stem Cross Section

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

Pine Life Cycle

Pine Ovule - Longitudinal Section

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

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

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

Phylum Gnetophyta  Third genus, Welwitschia, has only one species. - Confined to temperate deserts of southwestern Africa.  Average rainfall only 2.5 cm.  Plant use CAM photosynthesis. - Only produce two leaves throughout their life span.

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

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

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

Copyright © McGraw-Hill Companies Permission Required for Reproduction or Display