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 Photo A shows a juniper tree with a gnarled trunk. Photo B shows a sequoia with a tall, broad trunk and branches starting high up the trunk. Photo C shows a forest of tamarack with yellow needles.. Photo D shows a tall spruce tree covered in pine cones. Photo B. Photo C Part D
Conifers are the dominant form of vegetation in cold or arid environments and at high altitudes. Shown here are the (a) evergreen spruce Picea sp., (b) juniper Juniperus sp., (c) sequoia Sequoia Semervirens , which is a deciduous gymnosperm, and (d) the tamarack Larix larcinia . Notice the yellow leaves of the tamarack. (credit a: modification of work by Rosendahl; credit b: modification of work by Alan Levine; credit c: modification of work by Wendy McCormic; credit d: modification of work by Micky Zlimen)

Cycads

Cycads thrive in mild climates, and are often mistaken for palms because of the shape of their large, compound leaves. Cycads bear large cones ( [link] ), and may be pollinated by beetles rather than wind: unusual for a gymnosperm. They dominated the landscape during the age of dinosaurs in the Mesozoic, but only a hundred or so species persisted to modern times. They face possible extinction, and several species are protected through international conventions. Because of their attractive shape, they are often used as ornamental plants in gardens in the tropics and subtropics.

Photo shows a cycad with leaves resembling those of a fern, with thin leaves branching from a thick stem. Two very large cones sit in the middle of the leaves, close to the ground.
This Encephalartos ferox cycad has large cones and broad, fern-like leaves. (credit: Wendy Cutler)

Gingkophytes

The single surviving species of the gingkophytes group is the Gingko biloba ( [link] ). Its fan-shaped leaves—unique among seed plants because they feature a dichotomous venation pattern—turn yellow in autumn and fall from the tree. For centuries, G. biloba was cultivated by Chinese Buddhist monks in monasteries, which ensured its preservation. It is planted in public spaces because it is unusually resistant to pollution. Male and female organs are produced on separate plants. Typically, gardeners plant only male trees because the seeds produced by the female plant have an off-putting smell of rancid butter.

Illustration shows the green, fan-shaped leaves of Ginkgo biloba.
This plate from the 1870 book Flora Japonica, Sectio Prima (Tafelband) depicts the leaves and fruit of Gingko biloba , as drawn by Philipp Franz von Siebold and Joseph Gerhard Zuccarini.

Gnetophytes

Gnetophytes are the closest relative to modern angiosperms, and include three dissimilar genera of plants: Ephedra , Gnetum , and Welwitschia ( [link] ). Like angiosperms, they have broad leaves. In tropical and subtropical zones, gnetophytes are vines or small shrubs. Ephedra occurs in dry areas of the West Coast of the United States and Mexico. Ephedra ’s small, scale-like leaves are the source of the compound ephedrine, which is used in medicine as a potent decongestant. Because ephedrine is similar to amphetamines, both in chemical structure and neurological effects, its use is restricted to prescription drugs. Like angiosperms, but unlike other gymnosperms, all gnetophytes possess vessel elements in their xylem.

 Photo A shows Mormon tea, a short, scrubby plant with yellow branches radiating out from a central bundle. Photo B shows a plant with large, teardrop-shaped green leaves. Photo C shows a plant with long, flat leaves radiating along the ground from a central part with pink buds.
(a) Ephedra viridis , known by the common name Mormon tea , grows on the West Coast of the United States and Mexico. (b) Gnetum gnemon grows in Malaysia. (c) The large Welwitschia mirabilis can be found in the Namibian desert. (credit a: modification of work by USDA; credit b: modification of work by Malcolm Manners; credit c: modification of work by Derek Keats)
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Watch this BBC video describing the amazing strangeness of Welwitschia.

Section summary

Gymnosperms are heterosporous seed plants that produce naked seeds. They appeared in the Paleozoic period and were the dominant plant life during the Mesozoic. Modern-day gymnosperms belong to four phyla. The largest phylum, Coniferophyta, is represented by conifers, the predominant plants at high altitude and latitude. Cycads (phylum Cycadophyta) resemble palm trees and grow in tropical climates. Gingko biloba is the only representative of the phylum Gingkophyta. The last phylum, Gnetophyta, is a diverse group of shrubs that produce vessel elements in their wood.

Art connections

[link] At what stage does the diploid zygote form?

  1. When the female cone begins to bud from the tree
  2. At fertilization
  3. When the seeds drop from the tree
  4. When the pollen tube begins to grow

[link] B. The diploid zygote forms after the pollen tube has finished forming, so that the male generative nuclei can fuse with the female gametophyte.

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Source:  OpenStax, Bio 351 university of texas. OpenStax CNX. Dec 31, 2015 Download for free at https://legacy.cnx.org/content/col11943/1.1
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