Succulents - Research Article from Macmillan Science Library: Plant Sciences

This encyclopedia article consists of approximately 2 pages of information about Succulents.
Encyclopedia Article

Succulents - Research Article from Macmillan Science Library: Plant Sciences

This encyclopedia article consists of approximately 2 pages of information about Succulents.
This section contains 406 words
(approx. 2 pages at 300 words per page)

The term succulent, when applied to plants, refers to those organisms that have very fleshy leaves or stems, regardless of whether they are adapted to dry habitats (as are most true succulents). Specifically, succulent plants are those that are strongly adapted to life in water and/or heat-stressed habitats, and are typically represented by members of certain plant families (see accompanying table). Plants that have evolved in very hot, dry conditions, or those that experience these conditions at certain times of the year, have evolved various structures, habits, and metabolic mechanisms to cope with existence in stressed habitats.

FLOWERING PLANT FAMILIES CONTAINING SUCCULENTS
Family Common Name Geographic Distribution* Number of Species (approximate) Examples of Succulent Genera
Agavaceae Agave family North America, Africa 625 Agave, Dasylirion, Nolina, Sanseiveria, Yucca
Aloaceae Aloe family Africa 440 Aloe, Gasteria, Haworthia
Aizoaceae Ice plant family Africa 1,300 Carpobrotus, Faucaria, Lithops, Pleiospilos
Asclepiadaceae Milkweed family Africa 2,000† Ceropegia, Huernia, Orbea, Piaranthus, Stapelia
Cactaceae Cactus family North and South America 1,600 Carnegiea, Ferocactus, Mammillaria, Opuntia
Crassulaceae Stonecrop family Africa, Asia, Europe 1,500 Crassula, Echevaria, Kalanchoe, Sedum
Didiereaceae Didieriea family Madagascar, Africa 11 Allauadia, Decaryia, Didierea
Euphorbiaceae Euphorbia family Africa, North America 5,000† Euphorbia, Jatropha, Monadenium
Portulacaceae Purslane family Africa, Australia, North and South America 250 Anacampseros, Ceraria, Portulaca
* For succulent members of the family.
† Approximately 450 species are succulent.
† Approximately 750 species are succulent.

Most succulents are xerophytes, that is, plants that have developed adaptive features for life in dry, often hot, environments. In addition to some shared features with nonsucculent xerophytes, succulent plants have acquired additional specialized features, independently, in several different plant families. The general characteristic of plants that have evolved succulence is the presence of large parenchyma cells in leaves or stems (and occasionally in roots) that serve the purpose of water storage. Furthermore, these plants may also possess one or more of the following adaptations to reduce water loss during periods of heat or drought stress: the presence of epidermal cells with thickened outer walls; increased accumulation of the waxy cuticle layer covering the epidermis; and the evolution of crassulacean acid metabolism (abbreviated CAM; this process delays gaseous exchange through stomata until nighttime, when temperatures are lower and water lost by transpiration is decreased).

See Also

Cacti; Deserts; Defenses, Physical; Photosynthesis, Carbon Fixation And.

Bibliography

Mauseth, J. D. Botany: An Introduction to Plant Biology. Boston: Jones and Bartlett, 1998.

Raven, Peter. H., Ray F. Evert, and Susan E. Eichhorn. Biology of Plants, 6th ed. New York: W. H. Freeman and Co., 1999.

This section contains 406 words
(approx. 2 pages at 300 words per page)
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Succulents from Macmillan. Copyright © 2001-2006 by Macmillan Reference USA, an imprint of the Gale Group. All rights reserved.