Symbiotic Relationship of the Orchid & Tree | Garden Guides
Colonisation and diversity of epiphytic orchids on trees in disturbed and A. & Garcio-Franco, J.G. () The relationship between tree size and epiphytic Harrison, E.R. () Epiphytic Orchids of South Africa - A Field Guide to the. An example of a beneficial, plant-plant relationship familiar to many gardeners is the Epiphytic orchids can also be found perched in trees in the rainforest; like. Habitats with a mixture of mature trees are suitable and essential for the conservation of viable populations of epiphytic orchids in settled areas.
An epiphyte is a plant that grows on another plant, neither harming nor helping it. For example, mosses can be epiphytic, growing harmlessly on tree trunks.
More exclusively epiphytic plants are the bromeliads and some orchids. Bromeliads are plants that commonly grow high in the branches of tropical rainforest trees. They are often found in the joint where a branch meets the trunk; there, fallen plant debris collects, providing a source of nutrients to the bromeliad.
Some species of bromeliad have cup-shaped leaf rosettes. The cup fills with water during the frequent rains, and the plant is able to use this supply to fill its water needs. Though bromeliads perch in the branches, they do no harm to the tree. Host Branches Epiphytes are not parasites to the plants that they live on, but rather obtain their nutrients and water from the air and rain while obtaining energy from the sun.
If it were a parasitic relationship, one plant would benefit at the host species expense. Epiphytes do not harm their host species by only using the host for support and epiphytes often benefit the host tree or plant. In some cases, host trees were able to grow aerial roots when their branches were populated by epiphytes, enabling them to take in water and nutrients that were collected in the dense layers formed over time by the epiphytes Kricher Living in the Canopy In order to survive, plants must be able to obtain water and nutrients.
Since they do not have roots in the ground, they have to be efficient in collecting rain and nutrients. Epiphytes form dense root systems that have a large surface area, enabling the plants to absorb rainfall.
Since water might be limited and there might be long lengths of time in which it is dry, many epiphytes such as orchids are able to store water in thick stems. Other epiphytes are able to collect water in their leaves, enabling them to have a supply of water during dry periods of time.
It is also important for epiphytes to collect nutrients. Nutrients are also available from dust and particles that are caught in the roots and nutrients from decaying organisms. There are several benefits of living in the canopy that give epiphytes an advantage. First, epiphytes are able to get much more sunlight in the canopy than they would be able to get when living on the ground.
- Orchid mycorrhiza
- Symbiotic Relationship Between an Orchid & a Tree
- Symbiotic Relationship of the Orchid & Tree
Since they live on trees, the epiphyte does not have to use energy to reach high into the canopy from the forest floor and compete with trees and vines. Reproduction is a benefit of living high in the tree canopies.
Wind, insects, and birds are all important factors in reproduction of most plants. The canopy is the liveliest place in the rainforest with hundreds of birds and thousands of insects.
The more organisms that come in contact with the epiphyte, the more likely that it will be pollinated and its seeds distributed. The wind is also very important to most epiphytes.
Orchid epiphytes have adapted to have hundreds of thousands of seeds that measure in microns that are able to float in the air over long distances and find a landing spot in another tree. Micro-ecosystems Epiphytes make up a huge part of the biodiversity in a rainforest.
Not only do epiphytes account for a large portion of foliage in rainforest, they also support other plants and organisms. Every epiphyte is a microhabitat, in which there can be a food web of arthropods and other animals. Non-vascular epiphytes such as bryophytes, liverworts, and mosses, can be a home for many arthropods. Young forests will accumulate dense coverings of these epiphytes on the bark and on the branches.
In old growth forests, epiphytic mats are formed from years of growth and the accumulation of particles and dead tissue.
Epiphytes: An ecosystem contained within an ecosystem FINAL
These mats tend to contain insects including mites, springtails, beetles, ants, moth larvae, thrips, bark lice, wasps, and spiders.
These fungi come from a range of taxa including Ceratobasidium RhizoctoniaSebacinaTulasnella and Russula species. Most orchids associate with saprotrophic or pathogenic fungi, while a few associate with ectomycorrhizal fungal species. These latter associations are often called tripartite associations as they involve the orchid, the ectomycorrhizal fungus and its photosynthetic host plant. Some of the challenges in determining host-specificity in orchid mycorrhizae have been the methods of identifying the orchid-specific fungi from other free living fungal species in wild-sourced samples.
Even with modern molecular analysis and genomic databases, this can still prove difficult,  partially due to the difficulty in culturing fungi from protocorms and identification of fungal samples,  as well as changes in evolving rDNA. In particular, many fully mycoheterotrophic orchids associate with ectomycorrhizal basidiomycetes belonging to genera such as Thelephora, Tomentella and Russula. Basidiomycetes of the Atractiellales Ascomycota Though rare in orchids, ascomycete associations have been documented in several orchid species.
The European terrestrial orchid Epipactis helleborine has a specific association with ectomycorrhizal ascomycetes in the Tuberaceae. Orchid mycorrhizal associations involve a plethora of distinctive nutrient transport systems, structures and phenomenon which have only been observed in the orchidaceae family. These interactions are formed between basidiomycete fungi and all orchidaceae species . The basidiomycete fungi most commonly found associated with orchids, rhizoctonia, are known for their saprophytic abilities making this fungi orchid association anomalous, allowing both the plant and fungi to access a source of carbon within the mycorrhizal association not available in arbuscular mycorrhiza  .
The way and degree to which different orchid species exploit these interactions varies.
Orchid mycorrhizal interactions can range from wholly parasitic on the fungal partner, to a mutualistic interaction involving bidirectional nutrient transfer between the plant and mycorrhizal fungus  . Orchid plants have an obligatory parasitic life stage at germination where all of their nutrients must be supplied by a fungus .
Post germination, the orchid mycorrhizal interactions will become specialized to utilize the carbon and nutrients available in the environment surrounding the interaction. These associations are often thought to be dictated by the plant . It has been indicated in past studies that orchid plant individuals which inhabit dense highly shaded forests may depend significantly more on their fungal partner for carbon, varying within and between species, demonstrating the variable and reactive nature of these interaction.
Nutrient transfer interfaces and mechanisms[ edit ] At infection of an orchid by a mycorrhizal fungus both partners are altered considerably to allow for nutrient transfer and symbiosis.
Nutrient transfer mechanisms and the symbiotic mycorrhizal peloton organs start to appear only shortly after infection around hours after initial contact . There is significant genetic upregulation and downregulation of a multitude of different genes to facilitate the creation of the symbiotic organ, and the pathways with which nutrients travel. As the fungus enters the parenchyma cells of the orchid the plasma membrane invaginates to facilitate fungal infection and growth .
This newly invaginated plasma membrane surrounds the growing pelotons and creates a huge surface area from which nutrients can be exchanged.
The pelotons of orchid mycorrhiza are intensely coiled dense fungal hyphae that are often more extensive in comparison to endomycorrhizal structures of arbuscular mycorrhiza   . The surrounding plant membrane essentially becomes rough endoplasmic reticulum with high amounts of ribosomes and a plethora of transporter proteins, and aquaporins.
Additionally there is evidence from electron microscopy that indicates the occurrence of exocytosis from the plant membrane . This highly convoluted and transporter rich membrane expertly performs the duties of nutrient exchange between the plant and fungus and allows for molecular manipulation by ribosomes and excreted enzymes within the interfacial apoplast  . Pelotons are not permanent structures and are readily degraded and digested within 30 to 40 hours of their formation in orchid mycorrhiza.
This happens in all endomycorrhizal associations but orchid plants readily digest fungal pelotons sooner after formation and more often than is seen in arbuscular mycorrhizal interactions . It is proposed that the occurrence of this more extreme digestive pattern may have something to do with necrotorphic nutrient transfer which is the absorption of nutrients form dead cells. The key nutrients involved in the majority of the transfer between fungi and orchid plants are carbon, nitrogen and phosphorus .
Orchid mycorrhizal interactions are unique in the flow of nutrients. Typically in arbuscular mycorrhizal interactions the plants will unidirectionally supply the fungi with carbon in exchange for phosphorus or nitrogen or both depending on the environment  but orchid mycorrhizal nutrient transfer is less specific but no less regulated and there is often bidirectional flow of carbon between the fungus and plant, as well as flow of nitrogen and phosphorus from the fungus to plant.
In around species of plants there is no flow of carbon from plant and all of the nutrients of the plant are supplied by the fungus . That being said the net carbon gain by the plant in these interactions is positive in majority of the observed interactions .
Phosphorus Transport[ edit ] Phosphorus is a crucial nutrient needed by all plants and often phosphorus deficiency in soil will dictate the formation of a symbiotic relationship. Phosphorus is obtained by the mycorrhizal fungus from the surrounding soil in three different forms; organic phosphorus, phosphate, and inorganic phosphorus compounds.
Often times these compounds are strongly bound to cations and need to be protonated and, or catabolized to become bioavailable. Mycorrhizal fungi are extremely efficient at doing this due to their extensive soil surface area as well as high enzymatic diversity   .
Once freed from the soil the phosphorus compounds, primarily inorganic phosphate, are transferred through two proposed pathways.