Succulent plant

Not to be confused with Cactaceae.

Succulent plants, also known as succulents or fat plants, are water-retaining plants adapted to arid climates or soil conditions. Succulent plants store water in their leaves, stems, and also in roots. Geophytes that survive unfavourable periods by dying back to underground storage organs such as tuberous roots, corms, bulbs, and rhizomes, may be regarded as succulents.

The storage of water often gives succulent plants a more swollen or fleshy appearance than other plants, a characteristic known as succulence. In addition to succulence, succulent plants variously have other water-saving features. These may include:

Many succulents come from the dry areas of the tropics and subtropics, such as steppes, semi-desert, and desert. High temperatures and low precipitation force plants to collect and store water to survive long dry periods. Succulents also occur as epiphytes, "air plants", as such they have limited or no contact with the ground, and are dependent on their ability to store water. Succulents also occur as inhabitants of sea coasts and dry lakes, which are exposed to high levels of dissolved minerals that are deadly to many other plant species.

The best known succulents are cacti (family: Cactaceae). Virtually all cacti are succulents, but not all succulents are cacti. There is a significant difference between succulents that evolved in Africa and those that evolved in the Americas, the New World plants called cacti all have spines. No succulent plants arising in the Old World have spines although, through parallel evolution, there are similar species in the Old World that closely resemble species in the new world that do have spines. The functional nature of the shapes evolved independently in each hemisphere, even though the specific structures may differ. The spines of cacti arose from leaf structures. This process may be confused with convergent evolution that occurs in species that are related more closely.

To differentiate between these two basic types that seem so similar, but that are unrelated succulent plants, use of the terms, cactus or cacti, only should be used to describe succulents with spines. Popular collection of these types of plants has led to many Old World plants becoming established in the wild in the New World, and vice versa. One genus, Opuntia, is thought to have floated from the New World to the Old on equatorial currents and colonized itself in Africa, being described very early in botanical descriptions. Salt tolerance may have facilitated this process if early explorers were not responsible for transporting the plants.

Contents

Families and genera

Plant families and genera in which succulent species occur are listed below.

(succulent geophytes) Eulophia, Liparis, Oeceoclades
(geophytes) Acroliphia, Bartholina, Bonatea, Brachycorythis, Brownleea, Centrostigma, Ceratandra, Corycium, Cynorkis, Didymoplexis, Disa, Disperis, Dracomonticola, Eulophia, Evotella, Gastrodia, Habernaria, Holothrix, Huttonaea, Neobolusia, Nervilia, Plicosepalus, Pachites, Platycoryne

For some families, most members are succulent; for example the Cactaceae, Agavaceae, Aizoaceae, and Crassulaceae.

The table below shows the number of succulent species found in some families:

Family Succulent # Modified parts Distribution
Agavaceae 300 Leaf North and Central America
Cactaceae 1600 Stem (root, leaf) The Americas
Crassulaceae 1300 Leaf (root) Worldwide
Aizoaceae 2000 Leaf Southern Africa, Australia
Apocynaceae 500 Stem Africa, Arabia, India, Australia
Didiereaceae 11 Stem Madagascar (endemic)
Euphorbiaceae > 1000 Stem and/or leaf and/or root Australia, Africa, Madagascar, Asia, the Americas, Europe
Asphodelaceae 500 Leaf Africa, Madagascar, Australia
Portulacaceae  ? Leaf and stem The Americas, Australia, Africa

See also

References

  1. ^ Our South African Flora Ed. RH Compton (194?) Cape Times Ltd
  2. ^ Our South African Flora Ed. RH Compton (194?) Cape Times Ltd
  3. ^ Our South African Flora Ed. RH Compton (194?) Cape Times Ltd
  4. ^ Plants of Southern Africa Retrieved on 2010-1-1
  5. ^ FloraBase - The Western Australian Flora Retrieved on 2010-1-1
  6. ^ PlantZAfrica Retrieved on 2010-1-1
  7. ^ Australian Plant Names Index Retrieved on 2010-1-1

External links