FUNGAL RELATIONSHIPS WITH TREES

We are always researching science literature to discover new methods and ideas to help produce superior adapted trees and plants to survive climate change. I ran across the topic of mycorrhiza and, it turns out, the fungal/root inter relationships are quite intriguing.

Fungi are common throughout the forest ecosystems. Some fungi are common forest mushrooms, puffballs and truffles. Colonization of the area is from wind dispersion of their spores. Other fungi are not wind dispersed, but only found in the soil. Once fungus and plant root meet, a wonderful thing happens – a fungus root. These feet are known as mycorrhiza. These mycorrhiza create a symbiotic relationship between fungus and root.

Basically, there are 2 types of mycorrhiza relationships in the plant world. Endomycorrhiza and Ectomycorrhiza. By far, the largest mycorrhiza group is the Endo comprising approximately 80 – 90 % of the plant world. This includes most vegetables, grasses, flowers and fruit trees. The reason for these 2 classes of mycorrhiza is based on how the plant root is colonized by the fungus.

Endomycorrhiza penetrate the root tip cells of plants. Once penetrated, an arbuscule, is formed. An arbuscule is a finely branched structure within the root cell that acts as a major metabolic exchange site between the plant and fungus. The root tips actually swell to house these arbuscular structures. A truly symbiotic relationship develops where both the fungi and plant benefit. The fungus receives constant access to carbohydrates, such as glucose and sucrose, produced by the plant.

Benefits to the plant are huge. The mycorrhiza produce growth hormones that stimulate feeder root elongation and branching. By creating more arbuscules in the roots, these growth hormones are, indirectly, protecting roots against pathogens. First, the pathogens have no direct entry to the roots of the plants. The pathogens must pass through these arbuscules, a direct barrier, in order to gain root entry. Next, the arbuscules can produce antibiotics to some root pathogens to discourage entry. Lastly, arbuscules encourage increased plant health and, therefore, more resistance to disease. How?

Mycorrhiza enhance uptake of water and mineral nutrients, especially Phosphorus and Nitrogen. These uptakes from the soil are made possible due to the soil exploration of the hyphae sent out from the colonized root tips. It is estimated that these fungal hyphae can explore hundreds to thousands more volumes of soil than just root tips themselves. The fungi even interact and change the soil environment of the plant by improving the soil structure and quality. The filaments from the fungal hyphae create polysaccharides and protein that bind soils, increase soil porosity and promote aeration and water movement.

The second type of mycorrhiza are the Ectomycorrhiza. They comprise only 10 – 20 % of the fungal relationships of the plant world. However, to us at the nursery, this is a very important group since these associations are formed with many tree species, such as willow, oak, pine and spruce. Ecto are different from Endo because they do not penetrate the root cells but form a sheath or mantle around the root tip called the Hartig net. Though the root colonization may differ, the plants derive the same benefits as Endo colonization.

Surprisingly, in North America, few nurseries utilize mycorrhiza inoculation for their growing plant stock. It seems the natural thing to do, especially for the forestry industry. With climate change and changing ecosystems, mycorrhizal inoculating trees would produce more hardiness and increase tree survival rates. This year, is our test year at, Puslinch Naturally Native Trees, for mycorrhizal inoculation. We will keep you informed of our results.