Orchids growing on trees...?

I%26#039;m doing a project for my science class where we design our own plant. I%26#039;m drawing a plant in a rainforest and it%26#039;s going to be an epiphyte (don%26#039;t know if I spelled that right). I was inspired by the orchid flowers that grew on the trees for my plant. However, when we do this, we have to explain in detail about the pollinators and the seed dispersal. I was wondering, how should the seed be dispersed in order for it to successfully land on a tree branch? Can a seed just grow on a tree branch? How did the orchid start growing on the tree branch?

Orchids growing on trees...?
Orchids are the most numerous and successful of all flowering plants. Many live in tropical forests attached to trees as epiphytes, but there are ground living kinds on every continent except antarctica.





Tree living orchids live in association with special species of fungus which live in the orchid%26#039;s roots. The fungus penetrates tree bark and breaks it down. This releases small amounts of minerals necessary for the orchid%26#039;s growth. The minerals themselves came from the earth. They were carried up the tree and became part of the bark. The orchid keeps its fungus healthy by providing it with carbohydrates. Fungi can%26#039;t photosynthesize like plants, and rely on their orchid to supply them their food.





Unlike flowers like daisies or roses, orchid flowers usually have a single species of insect which polinates it. The insect polinates no other flower and the orchid has modified its form, fragrance and anatomy to accomidate this one species of insect. The structure of the flower usually exactly matches the porportions of the insect%26#039;s body so that the pollen is placed in the best spot to be delivered to the next flower.





Sometimes orchids even help the polination of other plants as well. Brazil nuts come from brazil nut trees. They grow in the Amazon rain forest. large tracts of forest were cut down and groves of Brazil nut trees planted. Curiously, none of them ever produced nuts. Extensive research revealed the pollinating species of bee only collected pollen once impregnated by the male bee. Females were only attracted to male bees if they were covered in an essential oil the males had collected from Gongorga orchids. These are very rare and the males had to fly many miles through the forst to find them. The scent of the male told the female he was strong and healthy enough to have found this orchid. When the original forest was cut down to plant Brazil nut trees, all the orchids were eliminated. The males could not find the perfume females required to allow them to mate. The female bees were never impregnated and hence, never pollinated the flowers of the Brazil nut tree. This was why the trees planted artificially never produced nuts. orchids frequently are involved in many associations with a number of different species, and this sophistication is why most scientists concider them the most evolved plants on earth.





Orchid seed is unique in the sence there is no food stored for the orchid embryo. Seeds like corn and beans have vast amounts of starch and oil available for the young plant to help it grow large enough to develop its own green leaves. Orchid seeds are just an embryo and a thin seed membrane. This simple design allows orchids to produce millions of seeds at a time. The seeds themselves are as fine as dust and carried away on the wind. If the seed lands within the vicinity of a beneficial species of fungus, the fungus penetrates the embryo and begins to provide it the minerals it needs. However, only a tiny number of seeds ever land where germination is possible. The orchid overcomes this by producing vast numbers of tiny seeds.
Reply:normally the seeds which are fine almost dust like would be dispersed by rain or wind. They need to land on the roots of where another orchid grows so that the bacteria that lives on the roots (or this may be found in wedges on trees in dead matter) will provide the means for the germination process otherwise the seeds won%26#039;t grow.





pollination is done by insects, birds, bats, moths. etc.
Reply:Scientists speculate the orchids took the trees to escape competition from other plants.
Reply:Orchid seeds are tiny and can disperse on the wind. Of course, not all will land where the conditions are right for them to grow, but each orchid seed pod contains thousands of seeds. Because of the large number produced, at least a few will get to the right places.





When an orchid seed germinates, it%26#039;s not growing on just tree bark. Leaves and debris collect in places where branched meet and cracks in the bark, and moss also grows on the trees. Birds, tree-dwelling mammals, and insects supply %26quot;fertilizer%26quot; by way of their droppings.





In rainforests where orchids live, the trees can grow so densely that little light reaches the ground. Orchids need to grow higher than ground level in order to get enough light for photosynthesis, so growing partway up a tree is an advantage. The first orchids may have been carried there by wind or birds. Of course, not all orchids are epiphytes (and you did spell that correctly!). In temperate forests, some species grow on the ground (lady%26#039;s slipper orchids for example), and Australia has two species of orchids which grow (and flower) completely underground.





Since your plant is something you%26#039;re creating, you could have small dust-like seeds like real orchids to be dispersed by wind, or have it be something eaten by tree-dwelling birds or insects that spread the seeds when they defecate.





NOTE: regarding Charles D%26#039;s answer, it%26#039;s a fungus, not a bacterium which associate with orchid roots. While the presence of other orchids indicate that the fungus would be present at that location, the presence of other orchids aren%26#039;t required - in fact, if too many orchids would grow in a single location, they would compete with each other for the few resources that exist. A large mass can break off a branch from their own weight, and without access to light, all would die.





And the need for the fungi is higher in the terrestrial species such as lady slipper orchids, but slight in epiphytes.


http://www.anos.org.au/groups/newzealand...


http://pubs.caes.uga.edu/caespubs/hortic...