Misconceptions of Mycorrhizas

Many biological products are out on the market that promise increased plant vigor, more fruit, and healthier plants. This posts hopes to clear up a little of the confusion on these, specifically, those containing mycorrhizal fungi. 

So what are mycorrhizal fungi??

In the most basic sense, these fungi live in the soil and beneficially associate with plants. These fungi have what is called a "mutualistic relationship" with the plant they inhabit. Each player gives a little to the benefit of the other. Depending on the feeding strategy organisms receive carbon (essential ingredient of our metabolic processes) from various sources. Plants take up carbon in the form of carbon dioxide from the air, decomposer fungi receive carbon from wooden logs by excreting enzymes. Mycorrhizal fungi need carbon as well, but they often get this from their "hosts" or in other words the plant shares the carbon (sugars) it produces with the fungi! So what does the plant get out of this? Well, quite a bit actually. Plants receive nutrients, a larger area to access nutrients from, disease protection, and even assistance with drought tolerance. Nice deal for both parties!

The quintessential mycorrhiza on pine tree cover photo on Smith and Read's, Mycorrhizal Symbiosis. 

They are several groups of mycorrhizal fungi, but the two main are arbuscular mycorrhizal fungi or AMF (formally known as vesicular-arbscular mycorrhizas or VAM), which grow into the plant cells. This makes them endomycorrhizal. The AMF fungi have a "tree-like" structure that can be seen inside the cells where nutrient exchange takes place. The other main group is ectomycorrhizal fungi (EMF). These fungi grow into the plant, but grow around the cells.

Arbuscule inside a plant cell. Photo credit - Shachar-Hill Lab MSU (http://shachar-hill.plantbiology.msu.edu/?page_id=44)

Ok, so here we go back to the main point of this blog entry. The two main groups AMF (endos) and EMF (ectos) are associated with different types of plants. Over 80% of Earth's plants have a mycorrhizal association. However, AMF's association is only with certain plants (typically herbaceous/non-woody) and EMF's associate with the other plants (usually woody plants). Note: Every now and then there is some cross-over, but I'll go over that in a future posting.  Ok with the concept of host-specificity in mind (certain mycorrhizae associating with certain plants) we start to look at what certain products are providing to you as the consumer.

Ectomycorrhiza on a root. Photo credit: Mycorrhizal Associations (http://mycorrhizas.info/ecm.html)

I have seen these biological products that are designed for specific plants (citrus, turf, roses, etc). These products are providing both AMF and EMF in these products when in actuality only AMF fungi are appropriate. The addition of both of these types of fungi will not hurt your plants and if the company supplying the product wants to provide both then fine. However, what is not helpful to you the consumer is that these companies are making you think that more organisms = better product. In actuality, adding proper organisms, not more, may be a better approach!

If you are interested in which mycorrhizal group your plants fall into, please click on the following link: http://californiamycorrhiza.com/lists.html

There is a lot to be learned about microorganisms in soil, but hopefully what we do know (as in the case of mycorrhizas) can be applied in more of a scientific approach to help you grow the best plants possible! What are your thoughts on biological products with mycorrhizas that you have used? Yea or nay?

Passion for the ignored, misunderstood, and disregarded...

Soil science was something I stumbled upon the summer between my sophomore and junior year of college. I began working for a government agency with an amazing group of scientists that had devoted their lives to exploring the universe below our feet. Up until this point I had noticed soil as "brown," which looking back astounds me. I had gone hiking with my parents as a young child, attended summer camp, been indoctrinated at a young age that saving paper = saving trees, so I had a well developed appreciation for the outside world. How I had never noticed that which lies beneath my feet still boggles my mind. 

However, the real love affair began when I started graduate school. The excitement my professors had for soil science was something I had rarely experienced during my education. Every now and then I would find a teacher who inspired (obviously I found a few along the way otherwise science would not have been my preferred path in school), but to find a whole group of people that couldn't get enough of digging soil pits, discussing research, and getting their hands dirty was a whole new world for me. During this time I fell head over heels in love with SOIL. What I had viewed as just a "brown" surface became this dynamic, 3-D ecosystem full of chemical and physical processes, living organisms, and variable environmental conditions reflected in more colors than I ever could have imagined. 

Through my education, I found that soil played a role in virtually every aspect our lives. From food and water to clothing and shelter, soil is connected to even the most basic parts of our lives and cannot be ignored.  Despite its ubiquitous appearance, soil is not an unlimited resource and needs more people to "heart" it. With this blog I hope to shed some light on this complex world below your feet and frankly, my dear, to inspire you to give a damn...