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Gymnosperms: “naked seeds” • • • • Cycadophyta Ginkophyta Coniferaphyta Gnetophyta Seed plant recap: derived traits • Reduced—microscopic—gametophytes • Protected within sporophyte • Dependent on sporophyte for nutrients Protection of gametophyte from environment • Heterospory • different male and female reproductive structures • Ovules (develops into seed) • Pollen (containing sperm) Protects sperm and allows fertilization w/o water Protects and enhances embryo survival Gymnosperm Origins • Fossil evidence for seedplants 360 m.y.a. • Among the Carboniferous forests of seedless vascular plants • Fossil evidence of extant Gymnosperms ~ 305 m.y.a. • Drying climate 299-251 m.y.a. created environment where seedplants had an adaptive advantage proliferation of gymnosperms • Extant Angiosperms arose 200 m.y. after extant gymnosperms Gymnosperm diversity 4 taxa • Cycadophyta • Ginkophyta • Gnetophyta • Coniferaphyta – primary model Cycadophyta (cycads) • Very prolific in Carboniferous period • Flagellated sperm w/ in pollen tube • Palm like w/ stroboli (cones) • 200+ species • Highly threatened today Ginkophyta (Ginkos) • Flagellated sperm w/ in pollen tube • Deciduous • Looses leaves • Separate male and female plants (dioecious) • Females produce a fleshy seed that is stinky and undesirable…vomit like • 1 species (not found in wild) • Long lived (up to 2500 yrs) Gnetophyta • Non-flagellated sperm • Usually dioecious • Similarities w/ angiosperms • Has vessel members • Double fertilization • ~70 species Welwitschia Distribution of Gnetophyta genera gnetum ephedra welwitschia Coniferaphyta (Conifers): pines, firs, cedars, junipers, spruces, etc. Coniferous forest dominated regions of world Conifers • • • • • ~600 species Mostly Northern Hemisphere—high latitudes & high altitudes/elevations Non-flagellated sperm Mostly Evergreen Needle like or scale like leaves • Clusters of needles organized by fascicles • Cold Adapted • Many are mycorrhizal dependent • Commercially important • • • • • Lumber/timber-- Softwood (no fibers and thin tracheid walls) Paper/wood pulp Pine tar Resin turpentine Southern Hemisphere Conifers Pine Needle Pine Needle Cones = stroboli • Most plants are monecious • Separate male and female cones Male Cones & Pollen Formation Pine Seeds: mostly winged some wingless varieties (birds, pine nuts..yum)
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