Gymnosperms

Gymnosperms Similar to angiosperms in that they produce a seed All gymnosperms (an angiosperms) are considered heterosporous Produce two types of spores: microspores and megaspores Gymnosperm means “naked seed” in greek meaning seeds are totally exposed or borne on the scales of female cones Examples: pine, spruce, fir, hemlock, ginkgo

Unique Gymnosperms This category includes some of the most interesting plants including giant sequoias, redwood trees, and bristlecone pines

Four phyla Coniferophyta Ginkgophyta Cycadophyta Gnetophyta Each has unique characteristics so let’s look at them closer!

Conifers About 630 species Most familiar group All conifers are woody trees that produce annual additions of tissue (annual rings) Produce resin a viscous, clear or translucent substance consisting of organic compounds. Helps protect plant from fungal or insect attack

Conifers Most conifer leaves are called needles that can be found in clusters or individually depending on the type of conifer Some leaves are scale like and cover the stem

Conifers Most conifers are evergreen meaning their leaves remain throughout the year Most conifers are monoecious meaning they have separate male and female reproductive parts in different locations on the same plant. Pares are found in the strobili or cone

Conifer Reproduction Female cones larger than male cones. 1. When a female cone is mature, it will open to allow the megasporangia to be exposed. 2. Male cones produce microspores that develop into pollen grains that are dispersed by the wind. 3. Pollen lands on exposed megasporangia producing seeds with papery wings to be dispersed for a new plant.

Cycads Most significant during the triassic period. Most species are extinct, but the ones that remain are tropical and subtropical plants Popular as ornamentals, therefore many species endangered

Ginkgo Only contains one living species: the ginkgo or maidenhair tree Named because of fan-shaped leaves resembling the maidenhair fern Oldest genus and species of living trees. Found to be at least 170 million years old Female ginkgo trees release a smell when the seeds mature therefore, some cities have ordinances against the planting of female trees because of their stench

Gnetophytes Contain more efficient water conducting cells in their xylem called vessel elements Cone clusters resemble flower clusters Some have seeds that are fleshy and resemble fruits from flowering plants

Ecological and Economic Importance Conifer forests provide stabilization of soil Trees used for christmas trees, timber, medicinal products, resins, and varnishes