UNDERSTANDING GYMNOSPERMS JRMG 2008 2009 What are GYMNOSPERMS

UNDERSTANDING GYMNOSPERMS JRMG 2008 -2009

What are GYMNOSPERMS? • • • gymnos - naked + spermae - seed have seeds (not fruits or flowers) developed (Paleozoic Era) dominant: Mesozoic Era (early ) heterosporous seed ferns Cone bearing plants

GYMNOSPERMS • 700 living species – conifers (such as pines and spruce) – cycads (such as the sago palm, Cycas revoluta) – ginkgos (the maidenhair tree, Ginkgo biloba) – gnetophytes (such as Mormon tea, Ephedra)

DIVISION GNETOPHYTA • 70 species (3 genera) • Welwitschia – two huge leathery leaves • Ephedra – Mormon tree • Gnetum – leaves angiosperm-like – vessels in the xylem • considered an angiosperm characteristic

DIVISION GNETOPHYTA • have some angiosperm-like features • Cladistic analyses support placement of the gnetales (or some portion of them) as outgroups for the flowering plants

Welwitschia mirabilis

DIVISION CYCADOPHYTA • • • pinnate leaves and circinate vernation heterosporous cones are unisexual – dioecious • free-swimming sperm

DIVISION GINKGOPHYTA • Ginkgo biloba – the maidenhair tree • dioecious • males are more commonly planted – females produce seeds that have a nasty odor • pollination is by wind • swimming sperm

DIVISION CONIFEROPHYTA • Most common gymnosperms • Pines, spruces, firs, cedars, sequoias, redwood and yews • Can live more than 4000 y. o.

DIVISION CONIFEROPHYTA • • • evergreen needle-like leaves Needles have a thick cuticle sunken stomates reduced surface area