Have you ever thought about what plants are made of? I mean, really thought about it. Strip away all the splendor and glory of all the different plant species on this planet and really take a close look at how plants grow and make more plants. It is a fascinating realm and it all has to do with photosynthesis. To go from photons given off by our nearest star to a full grown plant is quite the journey and, at the end of that journey, you may be surprised to learn what plants are all about.

It starts with photons. Leaving the sun they travel out into the universe. Some eventually collide with Earth and make their way to the surface. Plants position their leaves to absorb these photons. Energy from the photons is used to split water molecules inside the chloroplasts. In the process of splitting water, oxygen is released as a byproduct (thanks plants!). Splitting water also releases electrons and hydrogen ions.

These electrons and hydrogen ions are used to make energy in the form of ATP. Along with some electrons, ATP is then used in another cycle known as the Calvin cycle. The point of the Calvin cycle is to take in CO2 and use the energy created prior to reduce carbon molecules into chains of organic molecules. Most of the carbon in a plant comes from the intake of CO2. Through a series of steps (I will spare you the details) plants piece together carbon atoms into long chains. Some of these chains form glucose and some of that glucose gets linked together into cellulose.

Cellulose is the main structural component of plant cells. From the smallest plants in the world (genus Wolffia) all the way up to the largest and tallest redwoods and sequoias (incidentally some of the largest organisms to have ever existed on this planet) , all of them are built out of cellulose. So, in essence, all the plant life you see out there is literally built from the ground up by carbon originating from CO2 gas. Pretty incredible stuff, wouldn't you agree?

Photo by Jean and Fred licensed under CC BY 2.0

Are you ready to have your mind blown away? What you are looking at here is not some strange kind of mushroom, though fungus is involved. What you are seeing is actually the inflorescence of a parasitic orchid from Australia that lives and blooms underground!

Meet Rhizanthella gardneri. This strange little orchid is endemic to Western Australia and it lives, blooms, and sets seed entirely underground. It is extremely rare, with only 6 known populations. Fewer than 50 mature plants are known to exist. This is another one of those tricky orchids that does not photosynthesize but, instead, parasitizes a fungus that is mycorrhizal with the broom honey myrtle (Melaleuca uncinata). To date, the orchid has only been found under that specific species of shrub. Because of its incredibly unique requirements, its limited range, and habitat destruction, R. gardneri is critically endangered.

The flowers open up a few centimeters under the soil. They are quite fragrant and it is believed that ants, termites, and beetles are the main pollinators. The resulting seeds take up to 6 months to mature and are quite fleshy. It is hypothesized that some sort of small marsupial eats them and consequently distributes them in its droppings. Either way, the chances of successful sexual reproduction for this species are quite low. Because of this, R. gardneri also reproduces asexually by budding off daughter plants.

Despite not photosynthesizing, this orchid is quite unique in that it still retains chloroplasts in its cells. They are a very stripped down form of chloroplast though, containing about half of the genes a normal chloroplast would. It is the smallest known chloroplast genome on the planet. This offers researchers a unique opportunity to look deeper into how these intracellular relationships function. The remaining chloroplast genes code for 4 essential plant proteins, meaning chloroplasts offer functions beyond just photosynthesis.

I am so amazed by this species. I'm having a hard time keeping my jaw off the ground. What an amazing world we live in. If you would like to see more pictures of R. gardneri, please make sure to check out the following website:
http://www.arkive.org/underground-orchid/rhizanthella-gardneri/

Photo Credit: Jean and Fred Hort

Further Reading:
http://www.sciencedaily.com/releases/2011/02/110208101337.htm

http://www.eurekalert.org/pub_releases/2011-02/uowa-wai020711.php

http://www.environment.gov.au/cgi-bin/sprat/public/publicspecies.pl?taxon_id=20109