Orchids have lightest seed among the angiosperms and one of the reason for that is the lack of endosperm, that is the, reserved food material. So orchid seeds need external support to germinate. Here comes the role of mycorrhiza, a kind of fungi.
Fungi in turn are always very specific as we know that there are very specific fungi that infects specific fruits. This compatibility depends on the ability of the fungi to infect another organism, the composition of the cell wall of both. In case of orchids, first infection is when fungi gets associated with the seed. Such fungi or mycorrhiza are of two types, one which are very generalized, i.e., they can infect seeds from many species; second which are very specific, as they can infect very specific seeds. These fungal filaments or mycorrhiza links seeds with another plant and kind of helps in transfer of food from other plant (live or dead) to the orchid seeds. One more fact is, there could be more than one mycorrhiza associated with the seeds in one time. Now where this fungi is found is also very specific, a fungi growing in warmer temperature will not be found in cooler areas; a fungi growing in very high humidity will not be found in drier areas; and one of the most specific thing is, a fungi that is found in the litter of SAL tree leaves, may not be found on the TEAK tree leaves. So if there is a specific fungi which can infect orchid seed and is found in a SAL forests, then this also implies that the orchid will be found exclusively in the SAL forests and nowhere else. If the orchid and fungi have very generalized requirement then they tend to be very widespread. To meet up with all this fungal requirement, one orchid fruit holds millions of seeds, but yes the chance of survival is very low, but even if it is 5 % thats enough for every year. Fungi also acts as a kind of biological control otherwise with so many species and so many seeds, there would have been orchids growing in every corner of the world!!! NOTE: I am trying to use very simple and not technical words, so as to make it understandible to every one. Please feel free to question back if you dont understand any point. :) Best regards Pankaj -- *********************************************************** Pankaj Kumar, Ph.D. IUCN-SSC Orchid Specialist Group Asia Office: Conservation Officer Orchid Conservation Section Flora Conservation Department Kadoorie Farm and Botanic Garden (KFBG) Corporation Lam Kam Road, Tai Po, New Territories, Hong Kong. Residence: 151, 1st Floor, Tai Om Tsuen Lam Tsuen, Tai Po, New Territories, Hong Kong. email: [email protected]; [email protected] Phone: +852 2483 7128 (office - 8:30am to 5:00pm); +852 9436 6251 (mobile). Fax: +852 2483 7194 -- You received this message because you are subscribed to the Google Groups "efloraofindia" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/indiantreepix. For more options, visit https://groups.google.com/groups/opt_out.
