Thank you Dr Pankaj for this wonderful information in simple words. This mycorrhiza is specific and this is the reason that we can not grow orchids through seeds easily. A big lacuna is the case of *Dactylorhiza hatagirea*which is exploited from wild but can not be cultivated as we do not know the fungus exactly. DSRawat Pantnagar
On Thursday, October 3, 2013 6:45:15 PM UTC+5:30, Dr Pankaj Kumar wrote: > > 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] <javascript:>; [email protected] <javascript:> > 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.
