The gymnosperms (
The gymnosperms and
By far the largest group of living gymnosperms are the conifers (pines, cypresses, and relatives), followed by cycads, gnetophytes (
Some genera have mycorrhiza, fungal associations with roots (Pinus), while in some others (Cycas) small specialised roots called coralloid roots are associated with nitrogen-fixing cyanobacteria.
Diversity and origin
Over 1000 living species of gymnosperm exist.
All gymnosperms are
Conifers are by far the most abundant extant group of gymnosperms with six to eight families, with a total of 65–70 genera and 600–630 species (696 accepted names). Most conifers are evergreens. The leaves of many conifers are long, thin and needle-like, while other species, including most Cupressaceae and some Podocarpaceae, have flat, triangular scale-like leaves. Agathis in Araucariaceae and Nageia in Podocarpaceae have broad, flat strap-shaped leaves.
Cycads are the next most abundant group of gymnosperms, with two or three families, 11 genera, and approximately 338 species. A majority of cycads are native to tropical climates and are most abundantly found in regions near the equator. The other extant groups are the 95–100 species of Gnetales and one species of Ginkgo.
Today gymnosperms are the most threatened of all plant groups.
|Phylogeny of Acrogymnospermae|
A formal classification of the living gymnosperms is the "Acrogymnospermae", which form a
The extant gymnosperms include 12 main families and 83 genera which contain more than 1000 known species.
- Order Cycadales
- Family Cycadaceae: Cycas
- Family Zamiaceae: Dioon, Bowenia, Macrozamia, Lepidozamia, Encephalartos, Stangeria, Ceratozamia, Microcycas, Zamia
- Order Ginkgoales
- Family Ginkgoaceae: Ginkgo
- Order Welwitschiales
- Family Welwitschiaceae: Welwitschia
- Order Gnetales
- Family Gnetaceae: Gnetum
- Order Ephedrales
- Family Ephedraceae: Ephedra
- Order Pinales
- Family Abies
- Order Araucariales
- Family Araucariaceae: Araucaria, Wollemia, Agathis
- Family Podocarpaceae: Phyllocladus, Lepidothamnus, Prumnopitys, Sundacarpus, Halocarpus, Parasitaxus, Lagarostrobos, Manoao, Saxegothaea, Microcachrys, Pherosphaera, Acmopyle, Dacrycarpus, Dacrydium, Falcatifolium, Retrophyllum, Nageia, Afrocarpus, Podocarpus
- Order Cupressales
- Family Sciadopityaceae: Sciadopitys
- Family Microbiota
- Family Taxaceae: Austrotaxus, Pseudotaxus, Taxus, Cephalotaxus, Amentotaxus, Torreya
- Order Cordaitales
- Order Calamopityales
- Order Callistophytales
- Order Caytoniales
- Order Gigantopteridales
- Order Glossopteridales
- Order Lyginopteridales
- Order Medullosales
- Order Peltaspermales
- Order Umkomasiales(corystosperms)
- Order Czekanowskiales
- Order Bennettitales (cycadeoids)
- Order Erdtmanithecales
- Order Pentoxylales
- Order Czekanowskiales
- Order Petriellales
This section relies largely or entirely upon a
Gymnosperms, like all
seed plants, they are heterosporous, having two spore types, microspores (male) and megaspores (female) that are typically produced in pollen cones or ovulate cones, respectively. The exception is the females in the cycad genus Cycas, which form a loose structure called megasporophylls instead of cones. As with all heterosporous plants, the gametophytes develop within the spore wall. Pollen grains (microgametophytes) mature from microspores, and ultimately produce sperm cells. Megagametophytes develop from megaspores and are retained within the ovule. Gymnosperms produce multiple archegonia, which produce the female gamete.
During pollination, pollen grains are physically transferred between plants from the pollen cone to the ovule. Pollen is usually moved by wind or insects. Whole grains enter each ovule through a microscopic gap in the ovule coat (
The first published sequenced genome for any gymnosperm was the genome of Picea abies in 2013.
Gymnosperms have major economic uses. Pine, fir, spruce, and cedar are all examples of conifers that are used for lumber, paper production, and resin. Some other common uses for gymnosperms are soap, varnish, nail polish, food, gum, and perfumes.