|Succulent flora of Saudi Arabia.|
Succulent plants are of great ecological significance particularly in arid and semi-arid parts of Saudi Arabia or the Arabian Peninsula in general. They store water in their stems, leaves or roots, a characteristic feature adopted by several plants to withstand high temperature and low precipitation. Succulent plants are usually seen in the eastern slops of southern Hijaz Mountains, along the Arabian Gulf and Red Sea coast, shallow depressions and dry lake beds containing high levels of dissolved minerals that are noxious to other plants. In Saudi Arabia, approximately, 290 species belonging to 23 families are generally recognized as succulent. Some of the families, representing succulent species are Aizoaceae, Aloaceae, Asclepiadaceae, Cactaceae, Chenopodiaceae, Crassulaceae, Dracaenaceae, Euphorbiaceae, Portulacaceae and Zygophyllaceae.
Some of succulent plants have ornamental value (Adenium arabicum, Duvalia spp., Huernia spp., Caralluma spp., Euphorbia spp.) while a few other species (e.g. Sansevieria- Dracaenaceae)are economically important in local fiber industry or are deeply associated with the culture of the country. In Saudi Arabia, Asclepiadaceae is the largest family with over 27 species followed by Chenopodiaceae and Aloeaceae with 24 species each, majority of which are seen in the northwestern and southwestern regions. Aloe is the largest succulent genus in Saudi Arabia, containing about 24 species. The most popular among them are Aloe vera var. officinalis, Aloe sabaea, etc.. Species such as Aloe armatissima Lavr. & Colle, Aloe porphyrostachys Lavr. & Colle., Aloe shadensis Lavr. & Colle. and Aloe sheilae Lavr. are endemic to Saudi Arabia.
Euphorbia species are generally regarded as poisonous and spiny, some of them are as tall as 5 meters. Genera such as Caralluma, Caudanthera, Borelluma, Duvalia, Heurnia etc. of Asclepiadaceae have 4-5-sided succulent stems and possess very attractive flowers seen either singly or in clusters.
Agavaceae contains only 2 genera, namely Dracaena and Sansevieria. The former (Dracaena ombet) is found in the high altitude areas while the latter, represented by two species (S. ehrenbergii and Sansevieria forskaliana) is usually seen in low lying areas. Members of Agavaceae are of considerable economic importance in the Arab World because of their fibrous leaves/stems which were widely used in making mats, baskets, hats, etc. All three species have a scattered distribution in the south western region. Cactaceae, a New World family, is represented in Saudi Arabia by two exotic species, Opuntia dellenii and O. ficus-indica. Both species are now invaded into large tracts of the vegetation-rich areas of south western mountains. Crassulaceae is a relatively small family in Saudi Arabia. All members (4 genera and 16 species) of this family in Saudi Arabia are leaf succulents and are seen among the high altitude areas of Hijaz Mountains. Umblicus spp. and Sedum spp. are moist loving plants, usually found among Pteridophytes.
Portulacaceae is represented by 2 genera and six species of annual or perennial herbs. Members of this family are characteristic of 2-phyllous floral involucre (sometimes considered as sepals) with scales or hairs at the leaf bases. The most prominent among them is the widely distributed, edible plant, Portulaca oleracea which is found in almost all semi aquatic habitats of Saudi Arabia. In Zygophyllaceae, two genera are succulent. Among these Nitraria retusa is reported from the eastern province while the genus Zygophyllum (Tetreana) with six species have a wider distribution, commonly seen in saline habitats.
Succulent species of Chenopodiaceae are also important in arid regions, some of which are extremely fleshy while a few genera, for example, Salicornia and Halocnemum have articulated stems with no leaves. In genera like Salsola, Haloxylon, etc the leaves are scale-like and are distributed in the arid regions or in the coastal and inland sabkhas (Salty areas).
Angolluma commutata ssp. sheilae
Sulcolluma shadhbana var. barhana