What is so special about the Orchidaceae?
According to Greek mythology, there once was a satyr named Orchis who was celebrating in the festival of the god of wine. Having had too much to drink, he attempted to rape a priestess and as a result was killed by angry villagers. Orchis’ father prayed to the gods to bring his son back but the gods, being not especially fond of rapists, only returned Orchis as flowers. Thus, according to the Ancient Greeks, was the origin of orchids. However, with modern genetics and the theory of evolution, we know that it is unlikely that members of the Orchidaceae family are the restoration of a satyr. However, this does not dampen the mystical fascination of humans with this family of flowering plants. Undeniably, the beauty of many members of Orchidaceae has mesmerized many and led to a huge floricultural industry in the trade of orchids and its hybrids. Vanilla, one of the most used flavourings, is derived from the seed capsules of orchids. Orchidaceae is a special family not only because of its cultural and commercial importance, but also due to its unique structure and diversity. Members of this family have also formed special relationships with other species of organisms that are non-human. Orchidaceae is a large and diverse family, making it perhaps one of the most special.
It is estimated that members of the Orchidaceae family make up one tenth to one sixteenth of all species of flowering plants (Dressler). In 1973 it was predicted that 17,000 species existed (Willis) but that number has increased and it could now easily be between 20,000 and 25,000. This makes the Orchidaceae the largest family of flowering plants. However, this is not the only reason why they’re special. Orchids produce many small and light seeds that are easily dispersed by wind. While most seeds only travel meters away from its parent plant, some seeds can travel vast distances (e.g. cross the Atlantic Ocean from Africa to South America). It is perhaps because of this ability that Orchidaceae is such a cosmopolitan family. Orchidaceae virtually exist in all habitats around the world apart from the arctic, Antarctica, and some extremely arid deserts. Due to this widespread diaspora, orchids diversified into many shapes and sizes. The range of the sizes of orchids is very large. The smallest orchid is perhaps the Platystele jungermannioides, which only grows to up to 7mm tall while the largest orchids are Grammatophyllum papuanum and Grammatophyllum speciosum, which grows to up to 3 meters long (Dressler). Orchids also vary in their lifestyle, that is, on the ground (terrestrial) or on another plant (epiphytic). It is estimated that a quarter of orchids are terrestrial, five percent are capable of both lifestyles, and the remaining are epiphytic. As majority of orchids are epiphytes, special adaptations are required for it to absorb nutrients from its surroundings in the absence of soil.
Orchids have some special structural differences that separate them from other plants. As previously mentioned, many orchids are epiphytes. Therefore, their roots are different to normal roots as to allow them to absorb nutrients from its surroundings. Orchids that are epiphytes are able to acquire the nutrients it needs from the air, rain, and debris that settles around the plant. However, such nutrients are still absorbed through the roots. Many orchid roots have a special layer known as the velamen radicum. The velamen radicum is an outer layer of cells on the roots that forms a spongy covering for the roots. This in turn, helps the epiphytic plant catch and hold water, from which its nutrients come from. The velamen radicum, however, is not unique to orchids and also found in some members of the families Liliaceae and Araceae. Terrestrial orchids also contain these velamen radicum layers on their roots but their roots also form storage organs known as tuberoids. Terrestrial orchids usually have two of these tuberoids, which...
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