Fungi - A World of Wonder
In middle school science class, you may remember being shown microscopic evidence of the abundance of life in a single drop of pond water. That "world within a world" wonder is very similar to this month's topic: Fungi.
From the single cell wonder that is yeast, to the largest organisms in the world—three-mile wide forest ecosystems where every tree, every plant, is networked throughout the soil to every other tree and plant—fungi are a world within a world, indeed.
Far from any simple classification like plant, animal, or mineral, fungi are a kingdom of their own. They are virtually everywhere and they are vast in number. Currently, science is able to name upwards of 140,000 to 170,000 species of fungi; a tiny proportion of the suspected 2.8 to 5 million fungi species on earth.
The Importance of Fungi in Agriculture
Fungi affect every aspect of life as we know it, but our focus here is agriculture. It sounds a contradiction, but fungi species are so numerous and so diverse, it can safely be asserted that we would not have agriculture without the benefit of fungi and yet, at the same time, the number one disease-causing threat to agriculture is fungi. It is also important to note that it is not quite so clearly defined as good or bad fungi. Nevertheless, for our purposes here, we will discuss fungi in terms of benefits and disadvantages.
Types of Fungi
Concentrating on soil, the following is in no way an exhaustive list, but it is important to note fungi are present in many forms in soil and among certain crops.
The most important are those that function as garbage disposal and resource redistribution agents, those that live within certain plants, those that function in concert within crops, and finally, those that are pathogens or parasites, either harming or protecting plants.
Benefits of Fungi in Agriculture
Fungi are essential in the maintenance of any ecological system: the circular, constant movement from life to death, to decay, to recycling of nutrients to sustain life and so on and so on. Every terrestrial biome (specific home environment for living things suited for that place and climate), as well as every fresh water or marine biome teems with thousands of fungi species.
With other microorganisms such as bacteria, fungi break down the detritus of life, the dead, decaying complex organic compounds into simple, retrievable compounds. Fungi are able to do this under a wide range of soil types—more than bacteria can—and they do so, in part, because they have a huge enzyme capacity. Enzymes are proteins secreted by fungi that act as a catalyst to bring about a chemical reaction. In agricultural terms, plant residue—even woody plant residue—is decomposed by the action of enzymes emitted by fungi.
Nutrients such as organic phosphorus and organic nitrogen locked in plant residues are freed for use by future crops or by absorption into the soil to form humus, the organic part of soil.
According to the National Resources Conservation Service's publication on Soil Fungi, "fungi are important for immobilizing, or retaining, nutrients in the soil. . . so they help increase the accumulation of humic-acid rich organic matter that is resistant to degradation and may stay in the soil for hundreds of years."
Soil Structure, Soil Fertility
Fungi in soil usually grow as hyphae, a word for the long threads or strands, tubular in shape, that form a network of filaments referred to as mycelium. The mycelium has a vast surface area; one teaspoon of soil can contain as few as 10 and up to 100 meters of hyphae. The hyphae are very small, able to penetrate into tiny crevices and seek out nutrients while serving to create stable structure in the soil itself.
Living Together
Endo, meaning within, and phyte, meaning plants, are combined into the endophytes, used to denote an organism that lives within a plant. Many fungi are endophytes and are known to confer important properties to plants. This includes such things as the creation of chemicals that repel would-be grazers from feasting on a plant to giving a plant the means to tolerate drought, heat, and various diseases, even diseases stemming from other fungi.
Symbiosis
90% of all the plants we see in nature have symbiotic relationships with fungi through attachment to their roots. Another 19th century word, like most defined in this article, is mycorrhiza. Myco meaning fungus, and rhiza meaning roots, refers to this attachment. The fine hyphae grow into the soil to places, and at a distance, the roots of a plant cannot go.
When more than one plant, like an entire agricultural crop, are in a symbiotic relationship of this type, it is referred to as a mycorrhizal network. The nutrients gathered by the network are transferred to the plants by the root attachment. In exchange, sugars from the plants feed the hyphae. In this swap, both organisms benefit.
The nutrient resource "range" for the crop is significantly expanded and studies show the need for agricultural inputs is reduced when the mycorrhizal network is undisturbed.
Part of Skagit agriculture is exempt from this particular advantage because some crops cannot form mycorrhizal networks: spinach, beets, cruciferous vegetables, and others. Careful deliberation in cropping plans is required as the fungi do not survive without plants to partner with or without sufficient decaying organic matter to feed upon.
Good/Bad
As pathogens and parasites, fungi play many different roles in agriculture. On the plus side, the pathogenic/parasitic effect may actually apply to plant predators like insects, other types of fungi, or even certain diseases.
On the other hand, the amount of crop loss, either in the field, or in storage after harvest, caused by fungi far exceeds any other pathogenic threat.
Just a few include damping-off disease in seedlings, ergot disease in rye, apple scab, various diseases in cereal crops, and mummy berry in blueberries.
By Teresa Bennett: info@skagitonians.org