Significant Species Within The Asphodelaceae Family example essay topic

Asphodelaceae (Aloe Family) CLASSIFICATION Dahlgren et al. (1985) divided the Monocotyledons into several superorders of which the Liliiflorae is the largest. The order Asparagales is the largest of the five orders within Liliiflorea. One of the families within Asparagales recognized by Dahlgren and his co-workers was Asphodelaceae (Chase et al. (2000). Asphodelaceae consists of the sub-families, the Aspodeloideae and the Alooideae.

The Alooideae consists of six genera of which Aloe is the largest. The sub-family Alooideae are noted for their spectacular secondary growth, a characteristic used to define the Alooideae as monophyletic. On the other hand, some workers within the taxa have considered the above two subfamilies were for sometime, considered to be separate families, the Asphodelaceae and Alooideae (Dagne and Yenesaw 1994). Determining the proper phylogeny was difficult because some authors have argued that Aspodeloideae is not a monophyletic group. Also, the Aspodeloideae are more varied and share a great deal of morphological similarities between other groups (Chase et al. 2000).

The latest generation of chemical information on species belonging to these two groups is believed to reveal the relationships among the various taxa and to assist in establishing taxonomic classifications at various levels (Dagne and Yenesaw 1994). However, there is still not strong enough evidence suggesting both sub-families should not be included in a single family, the Asphodelaceae (Bisrata 2000). MORPHOLOGYAsphodelaceae is a distinct family from other monocot groups by a combination of several morphological and reproductive features: simultaneous, atypical ovular structure, lacking steroidal saponins, producing seeds with arils, and the general presence of anthraquinone's. Basic morphological features of genera within the Asphodelaceae consist of mostly herbs, shrubs, and sometimes arborescent, which grows into woody forms with trunks that can grow up to several meters high. The leaves are arrangement is alternate, spiral or 2-ranked that usually form rosettes at base or ends of the branches. The leaves are often thick and succulent with parallel venation.

The succulent aloes vary in size and morphology from the dwarf rosettes (Adams et al. 2000). Vascular bundles are arranged in rings around mucilaginous tissue, the bundles have aloin cells in inner bundle sheath near the phloem poles. The association of aloin cells and central gelatinous zones are for species with Alooideae (Judd et al.

1999). The perianth is usually bisexual and showy, with 6 distinct to strongly connate, non-spotted te pals. Reproductive flower parts have 6 distinct stamens and 3 connate carpels and a superior ovary that contain nectarines in septa. Fruits are almost always non-fleshy, or fleshy (Lomatophyllum), in a dehiscent capsule. The seeds are either winged, or wingless and contain a dry aril that arises as an annular invagination at the distal end of the funiculus (Judd et al.

1999; Watson and Dallwitz 1992). DISTRIBUTION AND DIVERSITY Asphodelaceae is a large genus containing 15 different genera and ~750 species (Judd et al. 1999). Accordingly the genera Aspodeline, Asphodel us, Bulbine, Bulbinella, Eremurus, Hemiphlacus, Jodrell ia, Kniphofia, Paradise a, Sime this and Tra chandra are placed in the sub-family Aspodeloideae while Aloe, Gasteria, Haworth ia, Lomatophylum and Poellnitzia are placed the Alooideae.

Most of the species are distributed throughout temperate to tropic regions of the Old World. The most diverse species are found in arid habitats in Southern Africa. Only two introduced taxa of Aloe are represented in the continental United States in parts of southern Florida and California (Judd et al. 1999) Aloe is the largest genus of ~400 species known to occur in a broad range of habitats mainly in Africa, Madagascar, and Arabia (Viljoen et al. 1998). Aloe is very distinctive group of plants noted for their often-spectacular secondary growth, which in many areas of tropical and southern Africa form the dominant plants (Chase et al.

2000). Aloe is common on rocky hill slopes, often in very large numbers where it creates a stunning winter display. In the southwestern Africa it grows in grassy and in southeastern Africa it may be found on the edges of the karoo. Aloe grows both in the open and in bushy areas and plants may also differ physically from area to area due to local conditions (Glenn and Hardy 2000). However, in study done by Britt et al. (2004) in Madagascar revealed that the rich Aloe diversity in their region has recently been under threat from habitat destruction.

ECONOMIC SIGNIFICANCE The most economically significant species within the Asphodelaceae family is Aloe. Aloe vera and Aloe fer ox are commercially sold for medicinal and cosmetic purposes (Dagne and Yenesew 1994). Several species within each sub-family are used as ornamental's, including Aloe, Hawthorthia, Gasteria, Kniphofia, and Bulbine (Judd et al. 1999) Aloe, a popular houseplant, has a long history as a multipurpose folk remedy. Commonly known as Aloe vera, the plant can be separated into two basic products: gel and latex. Aloe gel is the leaf pulp or mucilage, a thin clear jelly-like substance obtained from the tissue that makes up the inner bundle sheath cells.

The gel-like flesh from the inside of the leaves is used in cosmetic products and is reported to have wound healing properties. The plant has been used for topical treatment of wounds, minor burns, and skin irritations. American consumers are most familiar with aloe's use in skin-care products, but aloe can also be used as a beverage. Aloe products for internal use have been promoted for constipation, coughs, wounds, ulcers, diabetes, cancer, headaches, arthritis, immune-system deficiencies, and many other conditions (Wyk et al.

2000). Economic exploitation of South Africa's rich natural plant resources is limited. Currently only the indigenous flower industry has relatively successfully established small and medium scale entrepreneurs. The indigenous medicinal plant industry is large, but fully based on harvesting from the wild.

In order for medicinal plants to maintain their abundance, commercially used plants must be supplemented with cultivation (Wyk et al. 2000). HISTORY OF STUDY Currently many studies are being done concerning the cladistic gaps between taxa in the Asphodelaceae family (Rudall and Cutler 1995). Phylogenetic relationships of Asphodelaceae have recently been questioned because some genera do not strongly meet the criteria for being completely monophyletic (Chase et al.

2000). DNA analysis has been investigated extensively between the two sub-families and no strong evidence has been reached that supports making either its own family. As technology continues to advance, botanist will be able to establish accurate phylogenetic relationships for the future. Literature Cited Adams S.P., I.J. Leitch, M.D. Bennett, M.W. Chase, and A.R. Leitch. 2000. Ribosomal DNA Evolution and Phylogeny in Aloe (Asphodelaceae).

American Journal of Botany 87: 1578-1583. Bisrata D., E. Dagne, A. Viljoen and B-E van Wyk. 2000. Chemistry of Aloe Species. Department of Botany, Rand Afrikaans University Britt A., C. Club be, and T. Renarivelo. 2004.

Conserving Madagascar's Plant Diversity Blackwell Publishing pp. 258-266. Chase M.W., D.B. A nette, A.V. Cox, G. Reeves, P.J. Rudall, A.T. Johnson, and L.E. Eguiarte. 2000. Phylogenetic of Asphodelaceae (Asparagales): An Analysis of Plastid r bcL and trn L-F DNA Sequences. Annals of Botany 86: 935-951. Dagne E., and A. Yenesew.

1994. Anthraquinone's and chemo taxonomy of the Asphodelaceae. Pure and Appl. Chemistry 66: 2395-2398. Glen, H.F. & Hardy. D.S. 2000. Aloe.

Flora of Southern Africa. National Botanical Institute, Pretoria 5: 1-1. Judd W.S., C.S. Campbell, E.A. Kellogg, P.F. Stevens, and M.J. Donoghue. 2002.

Plant Systematics: A Phylogenetic Approach. Sin auer Associates, Inc. Van Wyk, B-E, van Oudtshoorn, B & Ge ricke, N. 1997. Medicinal Plants of South Africa.

Brita Publications, Pretoria. Viljoen, A.M., B-E. van Wyk, and F.R. van Heerd en. 1998. Distribution andChemotaxonomic significance of in Aloe. Plant Systematics and Evolution 211: 31-42. Watson L., and M.J. Dallwitz (1992 onwards).

The Families of Flowering Plants: Descriptions, Illustrations, Identification, and Information Retrieval. Version: 14th December 2000. web '.