Mycorrhiza for bonsai

What is mycorrhiza ? Mycorrhiza in bonsai soil Ectomycorrhiza Endomycorrhiza VAM mycorrhiza

What is mycorrhiza ?

Mycorrhiza means fungus root (mykes = fungus, rhiza = root). This term is as apt as it is misleading. Mycorrhiza is a close partnership between different fungi and plants, especially the roots of the plants. Such a partnership is called a symbiosis and is always entered into for the benefit of both partners. Every part does something and gets something for it.

The presence of mycorrhiza has long been known. Already in 1885, the reports of the German Botanical Society contained a detailed article on this subject. A lot of research has been done since then and a lot of information about mycorrhiza is available today.

For example, known that mycorrhiza is not uncommon in nature. It occurs very frequently and in many variants and enables both partners to assert themselves better in nature. Approximately 80% of all plants are able to form a symbiosis with mycorrhizal fungi. There are almost no tree species where mycorrhizae have not been found.

On the other hand, there are about 5000 types of mycorrhizal fungi. The fact that plants in poor nutrients and cold locations in particular develop them also points to the importance of a mycorrhizal symbiosis. It gives them a vital advantage there.

Mycorrhiza on a prebonsai (Sorbus aucuparia, rowan or mountain-ash) on the hot sunny side of the plant pot
⧉ Mycorrhiza on hot side of a pot

Many plants even have to rely on it and could not survive without the help of the fungus. These mycorrhiza-dependent plants include important bonsai tree species such as pines, azaleas, spruces and larches.

Mycorrhiza in bonsai soil

Mycorrhiza fungi for potting soil (also bonsai soil) are now produced on an industrial scale and are often added to the plant substrates (e.g. Cuxin bonsai soil) when they are packaged. Why is the bonsai friends often mixing the mycorrhiza with the bonsai soil, especially mineral substrates like Akadama, Kiryu and Kanuma ? What are the advantages of the the symbiosis for the mycorrhiza and the bonsai ?

The mycorrhizal fungal mycelium often extends over large areas. The connection with the tree root makes the soil supply of water and nutrient salts (for example from bonsai fertilizer) much better available for the plant. The bonsai plant is no longer limited to its own roots, but is also supplied with minerals dissolved in water by the fungus.

In addition, the surface of the root is significantly increased by the fungal mycelium, which also leads to improved water and nutrient absorption. Many fungi also secrete growth substances that stimulate the growth of the tree root.

Protons (hydrogen ions) are also released into the earth and, in return, mainly phosphate ions are absorbed. The phosphate is then also available to the plant.

But that's not all. The symbiont (i.e. the respective fungus) is also indirectly responsible for ensuring that the host (the bonsai tree) develops protection against parasitic fungi by encouraging the plant to produce antibodies against the fungi and thus increasing its resistance to root rot, for example.

The myccorhizal fungi, of course, are not entirely unselfish to their hosts. In contrast to plants, fungi cannot perform photosynthesis, i.e. do not gain energy from light. They are always dependent on the supply of organic material, be it dead (saprophytes, sapros = rotten, phyton = plant) or alive (parasital fungi, pará = next to; sitos = fattened). In the case of a symbiosis with plants, they receive carbohydrates (mostly glucose), vitamins and also growth stimulators.

Known mycorrhizal fungi are e.g. toadstools, tuberous agarics, porcini mushrooms or truffles. They prefer acid soils (pH 4-5). Soils with pH values above 7 usually have no mycorrhizal fungi.

What types of mycorrhizal fungi are there ?

Mycorrhiza is usually divided into 3 groups:

Ectomycorrhiza (= ectotrophic mycorrhiza)

In ectomycorrhiza, the entire fine root system of the plant is surrounded by a dense mycelium. The fungal hyphae penetrate into the bark of the root and form an intercellular tissue between the cells of the root epidermis. This tissue is used for the exchange of substances between plants and fungi.

Ectomycorrhiza is particularly common in pine bonsai, cypress and deciduous tree species such as beech (Fagus), hornbeam bonsai (Carpinus), birch (Betula), oak (Quercus), linden bonsai (Tilia), poplar (Populus), willow (Salix), chestnuts (Castanea) and myrtle (Myrthus).

It is striking that there are many different ectomycorrhiza fungi. In addition, a plant species can partially enter into symbioses with many ectomycorrhizae. At least 199 different symbioses were found on the birch. The fruiting bodies of many ectomycorrhiza fungi are well-known edible mushrooms (e.g. birch mushroom).

Endomycorrhiza (= endotrophic mycorrhiza)

In endomycorrhiza, the interaction between plant and fungus is even somewhat closer. Not only are the spaces between the roots of the roots traversed here.

An endomycorrhizal fungus penetrates directly into the root cells with its hyphae. This happens through enzymes that the fungus releases. The hyphae that have entered the cell are called haustoria. They are responsible for the mass transfer between the fungus and the plant.

A well-known plant that always occurs in symbiosis with ectomycorrhizal fungi is the blueberry. It usually grows on nutrient-poor and acidic soils and is absolutely dependent on its mycorrhiza. Even orchids cannot exist without mycorrhiza.

VAM mycorrhiza (= Vesicular-arbuscular mycorrhiza)

The name of the vesicular-arbuscular mycorrhiza stems from two properties that distinguish it from the other types of mycorrhiza: it forms vesicles and arbuscles (tree-like branched hyphae ends).

VAM mycorrhiza occurs most frequently and can be found in almost all plant families. Despite this great importance, there are only about 30 different types of VA mycorrhiza. These belong mainly to the genus Glomus and are able to enter into symbioses with a very large number of plants. Probably the most important, plant-physiological advantage of VA mycorrhiza is the increased supply of phosphate to the plant.

There is almost no plant family that is not associated with VAM mycorrhizas. The VAM mycorrhiza is often counted among the endomycorhizae. It is often difficult to make a precise distinction between the individual groups because there are many smooth transitions.

The VAM mycorrhizas are the most important group for the bonsai friend and should not be missing in a good bonsai soil.