Extension Communications
Extension 4-H Youth Building
Ames, Iowa 50011-3630
(515) 294-9915
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Extension Communications |
4/26/04
Contacts:
Nathan Brandt, Agronomy and Plant Health and Protection, nrbrandt@iastate.edu
Jean McGuire, Continuing Education and Communication Services, (515) 294-7033,
jmcguire@iastate.edu
Yard and Garden Column for the Week Beginning April 30, 2004
Friendly Fungi?
By Nathan Brandt
Agronomy and Plant Health and Protection Student
Iowa State University
Spring has brought with it the questions we ponder each growing season. Will this year be wet or dry, hot or cold? Do we risk planting anything with the hope that Mother Nature will take care of it for us? Having answer to these questions would be extremely helpful as consider what to plant in our yards and gardens.
In addition to replenishing rains and nurturing temperatures, Mother Nature also can provide "helper organisms," called mycorrhizal fungi, to promote vigorous plant growth. Many people worry when they hear the word "fungi" because they typically think of it as the mold that grows on bread when its left on the counter too long or the fungus growing at the base of an old, dying tree. Mycorrhizal fungi, however, usually are considered beneficial fungi. It is estimated that 95 percent of plants have mycorrhizal fungi of some sort associated with their roots. The word "mycorrhiza" literally means "fungus root."
Mycorrhizal fungi infect or invade plant roots to obtain necessary nutrients. But in return, these fungi assist the roots in uptake of minerals, most importantly phosphorus, from the soil. This added nutrient uptake may help plants deal with environmental and site-related stresses.
The increased nutrient uptake of roots infected with a mycorrhizal fungus occurs because the fungus forms a fine network of thread-like strands, called hyphae, that serve as an extension of the plant"s root system. There may be up to 10 feet of hyphae growing out from each half-inch of root that is infected by a mycorrhizal fungus. The diameter of the fungal hyphae can be one-fifth that of even the smallest root hair and may be many times longer, allowing it to explore areas of the soil not available to plant roots alone. Reaching these previously untapped nutrients in the soil gives the plant overall better nutrition and thus helps the plant reach its full potential. Mychorrizal fungi are especially beneficial in helping the plant access nutrients that aren"t very mobile in the soil, such as phosphorus and potassium.
These fungi occur naturally in the soil, but products containing mycorrhizal fungi can be purchased and applied to artificially introduce the fungi into soils. When applying these products, the hope is that the mycorrhizal fungi will increase plant growth and vigor and make them more tolerant to stresses, such as drought and soil compaction. There have been a number of scientific studies to examine the benefits of introducing mycorrhizal fungi into soils. However, results of these studies have not always shown a benefit to the plant when mycorrhizal fungi were artificially introduced into soils. Continued research is needed to define the specific conditions needed to maximize the potential benefits of adding mycorrhizal fungi to soils to promote plant growth.
For now, successful home gardeners should rely on time-tested practices that ensure healthy, happy plants. The best tip is to know the requirements of the plants that you hope to grow. When planting trees and shrubs, for example, it is particularly important to ----pick the proper plant species for the location, place it in the ground at the appropriate depth and provide it with water when needed. There"s nothing more satisfying than to stroll through your yard and garden and enjoy a view of thriving plants.
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ml: isugarden
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Editors: Two color photos, suitable for publication, are available at right. Click on each thumbnail photo to go to the fullsized photo. The top picture's fullsize photo is 160K and the bottom picture's fullsize photo is 208K. Caption: mycorrhiza 1 |
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| Caption: mycorrhiza 2 |  |