Christmas Bells

Christmas Bells
Christmas Bells - Blandfordia nobilis

Thursday, September 13, 2007

How Orchids are pollinated.

Instead of doing a demonstration with tiny native Orchids, I took the opportunity of using some Florist's Orchids (Cymbidiums) which were at the CTC as a result of a local Artist, Tanya Petra Daniels, having had a "launch" event for her art exhibition "Mish Mash" there. These photographs are roughly "life size" so you can see what is going on.
These are the typical large flowered Orchids which we all know, and love. And I concluded, rightly, that I could demonstrate how pollen is exchanged from the plant to an insect (my finger, in this case).

I could not see the pollinia within the flower, but I knew roughly where they would be located. That is above the point where a large insect (presumably a bee, or maybe a wasp) would go to investigate the flower. They poke around inside the flower, and as they back out, they brush against the prominent cap at the top of the "column".
I pushed the tip of my finger into the centre of the flower, then drew it back slowly. As I did so, a cap on the top of the part of the flower (the column), acted as if it was hinged. It lifted from the lower side, and, in so doing, my finger came into contact with the pollinia which are located inside that cover.
These dual grains of pollen are stuck onto my finger, with a form of natural glue, which was remarkably effective. Has any scientist or technologist investigated what is the nature of the glue which Orchids produce? I wonder. It "set" instantly on my finger and was quite strong. Amazing stuff, really.
Here you can clearly see the dual grains of pollen. If you look at the tip of my finger, you can see the white glue substance on top of my fingernail (directly under the two yellow grains of pollen - the so called "pollinia".) That name is used, for Orchid pollen to distinguish it from normal plant pollen, which is usually a fine dust. Orchid pollen is packaged this way, so that it is stuck onto the back of an insect, which is meant to transfer it to another flower.
If you follow this link, it will take you to a truly remarkable series of photos which show insects being "stuck" or "dobbed" with Orchid pollen. In some cases the photos show insects already bearing Orchid pollen, sitting on other Orchid flowers, ready to accidentally pollinate those flowers. I say "accidentally", for the insects are not aware of their role as "couriers" for the precious Orchid pollen which is stuck onto them. The insect come to the Orchid flowers because they have been attracted by the scents produced by these native Australian Orchids. These scents make the insects believe that the plant is in fact a female insect (usually a wasp), and the male insects attempt to mate with the flower. This is the process known as "pseudo-copulation".
According to an article which was published in the Sydney Morning Herald recently, there is another factor at play, other than scent. That is, the ultra-violet vision of insects. According to that article, we humans see the flowers and the insects as quite different. But, the reflected UV light from a flower of a specific Orchid species and the female wasp of the appropriate pollinating species, were examined through a spectrometer, and were found to be virtually identical. In other words, to a male wasp, the colours of the flower and of the female wasp make them appear identical. Strange, but true.
And, while searching for the text of the above story, on the Net, I found this really interesting story, which says that a fossilised bee has been found (preserved in amber) with a dob of Orchid pollen on its back. The amber is able to be dated, and it shows that Orchids have been doing this trick for some 20 million years.

Furthermore, this discovery has allowed scientists to use DNA analysis on the Orchid pollen, to estimate how long it has taken Orchids to evolve to the huge divergence we see in the Orchids of today. The estimate is between 76 and 84 million years - far older than anyone had thought. Scientists have hypothesised that Orchids, being highly evolved (adapted to highly specific environments and also features of their life cycles, such as their complex relationships with insects), are relatively new in the plant kingdom.

Seemingly not. Rather, they appear to have been around since the days of T Rex. Makes sense, I guess this figure allows them an awful lot of time to have trained the insects to be their sex-slaves.

Orchids come right at the end of the formal plant classifications. That is because those classifications work as a kind of family tree, which start with the so-called primitive plants, and move through to more "modern" plants. That classification might have to be revised, based upon this finding.

What price a single piece of amber with Orchid pollen in it? This piece of scientific information is virtually priceless.

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