Largest family of flowering plants Essay

Chapter 2

LITERATURE REVIEW

2.1 Orchids

2.1.1 Background of orchids

Orchidaceae likely belong to the largest household of blooming workss with 22000 to 35000 species covering approximately 700 to 800 genera distributed all over the continents between latitude 68° North and 56° South, except those utmost home grounds in the polar parts and in the driest parts. Among this great figure of species, orchids can be found in singular scope of sizes, an tremendous fluctuation in signifier, colorss and aroma. The orchids are believed by many that they are scentless due to the profuseness of the semisynthetic orchids which are largely scentless or feebly scented. ( Abdul Aziz et al. , 200 ; Kaiser, 1993 ) .

2.1.2 Historical background of orchid aggregation in Malaya

2.1.3 Hierarchy of formal nomenclatural classs

Classification becomes slippery without name. International Code of Botanical Nomenclature ( ICBN ) lists the classs of taxa that may be named. By the regulations of the ICBN, every systematic class receives a name stoping with certain postfixs ; the followers is an illustration of hierarchy terminology for orchids.

2.1.4 Categorization of Orchidaceae

Flower morphology, peculiarly the features of anther organisation has historically been the main support of orchid taxonomy. The categorization system of Robert Louis Dressler is the most comprehensive categorization to day of the month since that 1981 categorization was published in The Orchids: Natural History and Classification and include several amendments made in 1986 and 1990. This traditional categorization was unreal. The categorization presented in Phylogeny and Classification of the Orchid Family, 1993 which is based on phyletic analysis differs from that used in 1981. It is merely late flowered traits have been adopted in orchid categorization analyzed in a phyletic context.

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Orchidaceae are divided into five subfamilies characterized in portion by specialisations in the gynostemium or column. In Apostasioideae, two or three fertile stamens are formed and merely the radical portion of each fibril is united with the manner. In Cypripedioideae, the average stamen of the interior coil forms a big, plate-like staminodium, while the sidelong stamens are fertile. The subfamilies Vanilloidee, Epidendroideae, and Orchidioideae are monandrous.

Subfamily: Apostasioideae

Features:

Lip is similar to the petals, 2 or 3 fertile anthers, the sidelong anthers are fertile ; the average anther may be fertile, unfertile, or missing. A comparatively little group which include less than 20 species, limited to tropical Asia and Australasia.

Subfamily: Cypripedioideae ( Slipper orchid )

Features:

Lip deeply saccate ( pouch like ) ; sidelong anthers fertile, average anther sterile and shieldlike ; good represented in tropical Asia and tropical America.

Subfamily: Epidendroideae

Features:

Epiphytism, nowadays of pseudobulbs or corms, foliages can be distichous, caduceus, heavy and conduplicate, blossomings laterl, pollinia hard, anther shed. Some of these characteristics found in most epidendroid orchids but none of them found in all epidendroids. Epidendroid orchids signifier the largest subfamily.

Subfamily: Orchidoideae

Features:

Most have soft herbaceous foliages and rootstem tuberoids that combine some root construction with root construction to last during inauspicious periods. Pseudocopulation frequent.

Subfamily: Vanilloideae

Features:

Leafs typically fleshy, hempen or swollen into tubers. Lip free or with sidelong borders fused to column organizing a flowered tubing, anther monandrous, hyperincumbent, Mobile. It is distributed worldwide.

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