Orchids have generated a lot of fan following, with whole websites being dedicated to them, unlike other flowering plants. A lot has been said and researched on orchids. This may be because of huge diversity that is met within this plant group having over 800 genera which include thousands of species (not to forget about the new discoveries being made each year).
Orchids possess an amazing ability to adapt to diverse ecological niches, in other words, habitats. They are found in nearly all types of environmental conditions, you can find orchids growing in the tropics, temperate as well as alpine areas. Reports of finding orchids in the Arctic region also should not surprise us. This is a wide range of climatic zones. Most of the orchid species are found in the tropics, and the number of species decreases as we move towards colder temperatures. One of the adaptations of orchids of temperate regions is that they are used to lesser rainfall as compared to orchids of the tropics.
Three different types of habits are observed in orchids; terrestrial, epiphytic and saprophytic habit. Orchids can be seen growing on trees, rocks, dead/decaying matter and in soil. They have taken up different adaptive features to survive in these different habits. While the epiphytes have adapted their roots, stems and leaves according to their environment, terrestrial and saprophytes have adapted according their nutritional requirements too.
Morphologically, we see a lot of diversity in orchids. In case of roots, many orchids have a developed specialized root structure called velamen. The roots are sometimes seen forming nest like structures to store water. The roots of epiphytic orchids have the ability to attach firmly to the bark of the tree. Orchid roots form mychorrhizal associations with fungi to help in germination of seeds and supplement the general nutritional requirements. Stems of orchids may be reduced or even absent, sometimes these may swell up because of stored water and food materials. Sometimes orchid stems are known to take up the function of leaves (especially when leaves are absent); they turn green with chlorophyll and perform photosynthesis (production of food in the presence of sunlight). Leaves can be broad, thin, needle (like in Pinus), or may be absent, depending upon the availability of water.
Most morphologically diverse part of orchid is their flowers. The floral structure of sepals, petals and the reproductive parts show a huge variation. Sepals and petals are clubbed together under the name of tepals. These tepals are maybe similar in shape to each other or may be different. Labellum or the lip of the orchid flower is one the tepals. Sometimes the tepals are shaped such that the whole flower takes on a look of a bird (flying duck orchid) or an animal (monkey orchid) or a dancing girl or even like a slipper. Diversity is also visible in the reproductive organs; the column can be seen in some orchids to take the shape of bird or an insect.
So orchids show diversity in all aspects of their lives. If you have anything to add or you need any clarification, please contact me through the Orchid Forum or by the email link given below.