The Proper Relationship Between Orchids And Fungus
The orchid relies on its’ relationships with other organisms to assist in the overall health of the plant. One of these is fungi. They rely on fungi to assist in the germination of seeds and can form a partnership for the whole life of the plant.
Orchids which grow on trees form a relationship not only with the host, but with the orchid fungi they are reliant on. It makes you wonder what the implications would be for the orchid if it didn’t form this marriage.
The fungus lives inside the root cells of the orchid and this marriage of orchid and fungi results in a dual organism known as mycorrhiza. The roots of the orchid provide an ideal growing environment for the fungus, as it is devoid of competition and it is thought that the orchid provides the fungus with vitamins.
Parts of the fungus penetrate the root wall and has contact with the soil, which is rich in nutrients such as cellulose and other carbon compounds. This mixture is then broken down by many microbial guests into a soluble form which can be used by the orchid.
The millions of dust-like tiny orchid seeds can begin to germinate without the presence of fungus, however, the process is only complete once the fungus has infected the embryo. The marriage between the orchid and fungus is necessary at this point because the orchid cannot absorb nutrients from the soil and the tiny seed does not have any food reserves to sustain growth.
Once the orchid matures, there is still a reliance on the fungi to maintain the partnership, as some orchid species lack chlorophyll, so the dependency on each other can last throughout the lifetime of the plant.
An orchid found in North America, in only four states in the United States and in the south western area of British Columbia, Canada, is called the Cephalanthera austiniae or Phantom Orchid. It’s found mainly in old growth forests and is known to associate with one fungal family only.
The fungi forms associations with several species of trees, but it is not presently known which species are connected to the orchid-fungi-tree partnership.
The Phantom Orchid is a totally white orchid and even though it has a flowering stem, it primarily lives below ground and only sends the flowering stems above ground when the conditions are suitable. The orchid produces a low number of orchids which may occur primarily because of the climatic and pollinator limitations. If the growing conditions are severe then the species may be able to survive in a dormant state until the conditions improve.
In British Columbia, the Phantom Orchid occurs mainly in a coniferous forest, but it has also been found in forests dominated by the big leaf Maple Trees. This species of orchid has shown a tendency to live in sites with little or no under storey, which means little or no competition.
Recent studies have shown that even though some forest cover might be variable, there seems to be a preference for limestone sites. It has even been found adjacent to a limestone quarry in British Columbia, on heavily limed compost heaps and old shell middens. However some populations have no apparent association with limestone.
The partnership between the orchid and fungus can last a lifetime, and divorce can be lethal to the orchid. Scientists have tried to imitate the relationship between orchid and fungus, without success, which is a reason why so many species are now endangered. No-one has been able to replicate this wonderful partnership and if the fungi should die during experimentation, no amount of watering or fertilizing could save a dependent orchid.
