Mycorrhizal fungal filaments.
The seemingly magical properties of mycorrhizal fungi (aka ‘mycorrhizae’) are already fairly well known to soil growers. This special “root fungus” forms a mutualistic relationship with the roots of many plants, allowing them to access more water and nutrients. Mycorrhizae effectively extend the reach of the roots by forming a mycelial network that is able to extract tightly bonded water and nutrients (particularly phosphorus and iron) and translocate them back to the plant. The plant, in turn, feeds the root fungus with carbohydrates. Everybody’s happy – it’s mutual after all!
Ok, so that’s soil. But what about hydroponics? Nutrient manufacturers remain divided on the issue. Some recommend a completely sterile environment. That means no bacteria (beneficial or otherwise) and no friendly fungi. Why? Proponents of sterile growing environments argue that in hydroponics the grower is supplying all the nutrients their plants need in a directly accessible form and question the need for little ‘fungi helpers’ to assist in nutrient assimilation. (In hydroponics, all the nutrients are supplied in ionic, or directly accessible, form.) Similarly, the roots shouldn’t have to go out in search of water in hydroponics as it’s being provided in abundance. However, recent studies have shown that mycorrhizae can help plants uptake mineral-based nutrients too, promote with root branching, and massively extend the active feeding capacity of the feeder root tips.
Sound interesting? We thought so! So we asked mycorrhizae experts Mike Amaranthus PhD and Josh Eagan BS to give us the low-down on how this special root fungus behaves in a non-soil environment.
Fungus has a bad name going back a long time. The ancient Romans had a legend regarding a malicious boy who tormented a fox by tying wheat straw to its tail and then setting the straw on fire.The Roman god Robigus was so irritated that he penalized humanity with wheat rust, the fungal disease that leaves a farmer’s field looking as though it has been burned. For hundreds of years afterward, the Romans sought to pacify Robigus through sacrifices of dogs and cows with the misfortune of being born with rust-colored fur.
Modern hydroponic growers sacrifice too, increasingly by sacrificing plant quality and profits to prevent damage from a host of fungal “fiends” with names like black rot, club root, sclerotina blight, wire stem, sudden death syndrome, brown spot, and charcoal rot. Opportunities for using beneficial fungi as “friends” exist for the grower as well. The best documented friendly use is mycorrhizal fungal inoculum for improving plant nutrient uptake, plant quality, yields, and disease resistance.
THE FUNGUS FIEND
Most growers blame their nutrients when things start going horribly and unexplainably wrong. Big mistake! Pythium and phytophthora are two of the most common fungal diseases that can affect indoor growers, and they are not easy to spot until well advanced. Pythium-caused root rot is a real problem in hydroponic systems and is becoming increasingly common.
Pythium-infected Hosta plant.
Pythium is a waterborne fungus and recirculating hydroponic systems provide it with an ideal environment in which to live and breed. Plants can survive and grow with high levels of pythium spores in the nutrient solution. The fungus, however, will restrict the root system. A sudden rise in temperature will find the plants unable to increase their uptake of water and they will wilt. For many growers this is the first sign that pythium is active in their system. Damping-off caused by pythium affects growers growing in flats or in the propagation of cuttings. Damping off can attack and topple plants in just a few days. The lower stem becomes constricted and dark brown near the growth media’s surface, a symptom called wire-stem. The hydroponic grower can encounter pythium at any time and, if he is unprepared, he may well lose his crop. Pythium root rot can be caused by several different species of the fungal genera pythium.
Phytophthora, the notorious fungus that caused the Irish potato famine, causes annual crop losses in the tens of billions of dollars today. Beginning in 1845 and lasting for six years, the potato famine killed over a million men, women and children in Ireland and caused another million to flee the country. Phytophthora, from the Greek phytón (“plant”) and phthorá (“destruction”), is literally “the plant destroyer” that continues to plague a wide variety of crops globally with no effective means of chemical control.
Certain fusarium fungal species are also among the most dangerous root diseases in the world affecting hydroponic growers. There has been a dramatic increase in fusarium infection in the last several decades. The ability of this disease to form toxins that are poisonous to both humans and animals makes it a serious problem. The most visible symptom of these fungal diseases is in the root systems. Roots will begin to go brown and lose their healthy white appearance. As the pathogen spreads, the roots become soft and mushy and there is always a tendency for the plant to wilt in the warmer part of the day.
THE FUNGUS FRIEND
We can never purge the world of fungus, of course; nor would we choose to. Fungi represent a kingdom unto themselves, the fifth kingdom in fact. As a taxonomic dominion, kingdom is as high as it gets; animals, plants, bacteria, protists and our fungal friends make up the five.
Some 100,000 species of fungi have been described scientifically, and experts estimate that over a million remain to be discovered. Fungi have influenced our life in ways we take for granted. For a loaf of bread and a jug of wine we can thank the fungus saccharomyces, which is used in bakers’ and brewers’ yeasts. For recovery from infection we can thank the common soil fungus penicillium. Serendipity often leads to fungal discoveries. When Alexander Fleming discovered penicillin, he was trying to perfect an antiseptic formula based on nasal mucus. The nasal mucus formulation never did materialize (we can all breathe a sigh of relief!), but his unforeseen discovery of antibiotics changed the world.
What a difference a little mycorrhizal fungi makes! The tomato plant on the left was grown without mycorrhizal fungi, whereas the plant on the right was inoculated with mycorrhizal fungi.
Fungi also have a flair for symbiosis, for establishing cross-kingdom relationships that feed the fungus sugars while bestowing upon its partner new powers. Under natural conditions plants live in close symbiotic association with a group of soil organisms called mycorrhizal fungi. These fungi colonize plant roots and extend the root system into the surrounding soil. Estimates of amounts of mycorrhizal filaments present in growth media associated with plants are astonishing. Several miles of filaments can be present in less than a thimbleful of soil.
The relationship is beneficial because the plant enjoys improved nutrient and water uptake, disease resistance, and superior survival and growth.
It is this not-so-glorious association between plants and mycorrhizal fungi that keeps the whole show rolling in natural environments and can be an important tool for hydroponic growers. Approximately 90 per cent of all land plants depend on the mycorrhizal fungi that radiate from their roots and feed humbly on their plant sugars. In return, the fungus delivers nutrients to the plant like phosphorus, calcium, nitrogen, iron and life-giving water.
The mycorrhizal relationship is ancient and fundamental. In fact, in natural habitats, the presence of mycorrhizal fungi on the roots of plants is as common as chloroplasts to the leaves of plants. Botanists believe that plants might never have made the leap onto land some 460 million years ago without the assistance of Robigus and his mycorrhizal assistants.
This mutually-beneficial association between fungus and plant provides the fungus with relatively constant and direct access to carbohydrates, such as glucose and sucrose produced by the plant in photosynthesis. The carbohydrates are transferred from plant leaves to the root tissues and then to the fungal partners. In return, the plant gains the use of the mycelium’s very large surface area to absorb water and mineral nutrients from the soil, thus improving the mineral absorption capabilities of the plant roots. Mycorrhizal mycelia are much smaller in diameter than the smallest root, and can explore a greater volume of soil-less media, providing a larger surface area for absorption. Also, the cell membrane chemistry of mycorrhizal fungi is different from that of plant roots. The whole length of the mycelia is capable of absorption as compared to just the tips of the roots themselves. Plants grown in sterile soils and growth media often perform poorly without the addition of spores or “propagules” of mycorrhizal fungi to colonize the plant roots and aid in the uptake of soil mineral nutrients.
These mycorrhizal fungi are the best understood of the soil microbe families—and potentially the most useful to growers. Nearly all important crops form the mycorrhizal relationship, with notable exceptions including the mustard family, canola, broccoli, and sugar beets. Mycorrhizae attach themselves to plant roots and grow thread-like hyphae out into the surrounding soil, siphoning amino acids, nutrient molecules and water back to the plant. A grower benefits from mycorrhizal inoculation as it increases the effectiveness of added fertilizer and protects the root system from fungal fiends.
How do mycorrhizal fungi protect roots? The source of disease resistance is probably a combination of factors. The mycorrhizal fungus can present a physical barrier to the pathogenic fungus and/or produce antibiotics that limit the growth of the pathogen. Also, mycorrhizal-colonized plants develop more robust root systems that buffer the plant against the impact of pathogens.
It is also possible that the mycorrhizal fungus stimulates the host to produce chemicals that inhibit the growth of any other fungus on the root. In addition, because the mycorrhizal fungus is so adept at capturing nutrients, there are limited resources available for the growth of the disease fungus. Research has shown that, once a root is colonized by a mycorrhizal fungus, it is more resistant to infection by disease organisms.
INVITING A FRIEND TO DINNER
How do you inoculate mycorrhizal fungi to a hydroponic growing operation? Certain mycorrhizal spores (or “seeds”) of the fungus have been selected for their growth-enhancing abilities. The goal is to create physical contact between the mycorrhizal inoculant and the plant root. Generally, mycorrhizal application is inexpensive and requires no special equipment. Growers have at least three options to inoculate with mycorrhizal fungi.
Powder, liquid and granular forms of mycorrhizal inoculum.
The first method is an incorporation of a granular or powder form of the mycorrhizal inoculant into the growing media before planting. Secondly, the granular or powder inoculant can be placed into soil or soil-less mixes before placing the transplant into the planting hole, or distributed around the root ball after placement. The third option is a water-in drench. A powder is mixed with water, or a liquid is injected into the rooting zone through existing spray devices. In all three methods, all that is needed is for the mycorrhizal inoculant to reach the vicinity of the roots.
Fungi are omnipresent, occupying every ocean, the atmosphere, and the soil on every landmass. While some fungal fiends are “killers,” attacking living tissue they have infested, the vast majority are benevolent and, in many cases, vital to life forms around them. Fungi can be both fiend and friend to the hydroponic grower. While fungal diseases can impact the grower’s bottom line, mycorrhizal fungi can improve hydroponic yields and be a low-cost, natural solution to increasingly expensive chemical and disease control treatments. Certainly, using beneficial fungi in a hydroponic operation is a preferred alternative to the sacrifice of dogs and cows with rust-colored fur to Robigus!
Check out Urban Garden Magazine’s handy-dandy Mycorrhizae Q&A!
Got a question about mycorrhizae that we didn’t answer? Give us your best shot: post your question or comment below!
AM fungi will no sporulate or infect host roots if phosphorus levels are over 32 ppm, and over about 20 ppm hinders the AM fungi to a great degree.
Dear NA,
As is often the case in the field of horticulture and, for that matter, the wider universe, the truth is invariably a good deal more complex than we sometimes conceive it to be. There are over 20,000 studies of mycorrhizae and phosphorus uptake. Furthermore there are many different strains of mycorrhizae with different attributes. Some mycorrhizal species and strains are sensitive to high levels of available P, which can inhibit propagule germination, whereas other species and strains thrive in a moderate P environment. A quality mycorrhizae product is created by using strains that thrive in a moderate P environment.
Trichodema harazianum and T. konigii improved root growth and mycorrhizal colonization in several replicated trials. Is there a Trichoderma species that would compete with mycorrhizal fungi in a certain situation/environment? We asked Dr. Michael Amaranthus from Myco Apply. He reported that in his 35 year career he has never experienced this kind of thing. Nevertheless, we concede that it is possible. Again, it’s a question of species. I believe also that JH Biotech in Ventura would tell you that nutrient cycling with the tricos does, in fact, take place.
To better evaluate your comments, it would have been helpful for you to post citations of any scientific research or publications that back up your assertions or, at least, a valid email address to enable a private correspondence. I have posted some references to some studies that you may find informative: http://urbangardenmagazine.com/tag/research
Nb. If you had provided a valid email address we would have taken the opportunity to make a private request to you, asking you politely to refrain from posting insults (especially directed at our editorial and research team) on our public website. While the relative anonymity of communication via Internet forums can doubtlessly promote incisive debates and exchanges, we must also try not to let ourselves get carried away when it comes to asserting our opinions as objective facts, lest we embarrass ourselves very publicly!
To this end, we edited some of your comments. I hope you don’t mind.
Peace,
Everest
I have a couple of comments / questions.
First, I use non-organic nutrients in a hydroponic operation. I employ light doses of 3% H2O2 to keep the roots healthy and the waterways clean. Would it be possible to continue this practice without killing the mycorrhizal fungi, or would it be better not to inoculate with the fungi in this application?
Secondly, aside from improved root disease resistance, are there other benefits to the hydroponically grown plant? In my view, water and consumable nutrients are abundantly available to the roots in most hydroponic applications, so the “expanded root system” benefit of the mycorrhizal fungi may not be useful to the hydroponically grown plant. Since there are no organic materials in solution or in the medium (at least in my operation) the plant does not benefit from the ability of the fungi to break down the nutrient compounds so they are in a form that the plant can easily consume. The hydroponic nutrients are already in a form easily available to the plants. Are there other benefits to the non-organic hydroponic garden?
Innoculants usually come with a charge of carbohydrates, just enough to get them started into reproducing. Once they attach themselves to the root system, they will feed off the root zone exudates and dead root matter (yes, root death occurs constantly – a healthy root system reproduces faster than the rate at which it decays). So, you do not need to add any organic additives that may end up clogging drippers and misters. If you’re using ebb/flow, you can add humic acids or seaweed extract: mycos love that stuff! Just PLEASE don’t add any H2O2 when inoculating–the bennies will keep the population of nasties to marginal levels by out-competing them out of food. Some will even go to work on the bad ones or trigger immune responses at root level, where the plant will produce its own antibiotics. Beneficial microbes definitely have a place in hydro. I do not want to give away too much, but look out for our upcoming product tests, where we will be sharing our experiences testing a new microbial innoculant under a variety of growing media, settings, and conditions.
Addendum: several typos noted. Despite this, I stand by what was written and cite as a reference the book Teaming with Microbes.
Another thing worth mentioning: bacteria may be more beneficial than mycorrhyzae, depending on what you grow. Some annuals, for example, may benefit more from a seasonal fling with bacteria, whereas certain trees and perennials profit from a long-term relationship with fungi. This is not a hard and fast rule and I highly recommend reading the aforementioned book for a more in-depth look at which microorganism would better benefit what type of plant.
Eliab,
Do you know for a fact that H2O2 kills the beneficials? I have heard that it will only kill anaerobic bugs.
Yes I do. The oxydizing effect of h2o2 does not differentiate on whether the cell is aerobic or not. It may not be as strong as ethanol, but it will kill indiscriminately.
If you pour a dilute peroxide solution over a wound, you will notice the fizz. That fizz comes from the oxydation of, not only any potential pathogens, but from the oxydation of cells belonging to lacerated blood, tissue, and nerves. H2o2’s oxydizing action is not selective.
I used to use h2o2 when I spotted brown roots and it worked for a while each time and the brown roots would always come back. I then started using aquashied. It is beneficial bacteria and I’m simply amazed, large white roots and huge plants. Next I’ll try the GH b and and I’m thinking about the M which is mycorrhizae. Do you suggest using both bacteria and fungus at the same time?
I did understand the beneficial aspect of mycorrhyzae in rootzone, and I looking forward to apply for my next cropping cycles using coco coir as planting media. The problem is it is not easy to get the innoculant at my place. Is there any method that we can innoculate this fungus using existing plant’s roots colonised by M web and what are the plants that can be used.
thank you.
To Mohammad
you need to infect a donor plant then plant it next to the plant you wish to infect or you can buy expensive injection systems which shoot a gel into the root zone
Can anyone tell me neem oil or cake is ok to use with plants that have been treated with mycorrhizal fungi? My local grow shop owner said neen is a natural fungicide. Be good to know for sure…
I note that you are asking a detractor of the viability of mycorrhizae in hydroponics to post up links to research. Well guys surely you know there is reams and reams of research that crosses this and supports these claims – but I’m sure that a magazine would perhaps twist the facts. See below for some research; as you put it, it’s complex and in hydroponics it becomes even more complex with many experts on VAM reasoning that their effectiveness in hydroponic settings is extremely limited. See following…
Influence of Phosphorus on Mycorrhizae:
The benefits listed above are greatest in P-deficient soils and decrease as soil
phosphate levels increase (Schubert & Hayman, 1986).
Very high and very low phosphorus levels may reduce mycorrhizal
infection/colonization (Koide, 1991). It is well established that:
Mycorrhiza and soil phosphorus levels Colorado State University Cooperative Extension … Page 1 of 4
http://www.colostate.edu/Depts/CoopExt/TRA/PLANTS/mycorrhiza.html?PrintWindow 12/28/2004
infection by mycorrhizal fungi is significantly reduced at high soil phosphorus
levels (Amijee et al., 1989; Koide & Li, 1990)
the addition of phosphate fertilization results in a delay in infection as well as a
decrease in the percentage of infection of roots by mycorrhizae (deMiranda,
Harris & Wild, 1989; Asimi et al., 1989)
an increase in the level of soil phosphate results in a reduction in
chlamydospore production by the fungus (Menge, et al. 1978). These spores
are involved in root infection and spread of the fungus through the soil profile.
Please feel free to post condescending insults.
We do not mean to “twist the facts.” We even reference the high phosphorus levels inhibiting mycorrhizae propagule development in the article. So … not entirely sure what point are you trying to make here.
“Feel free to post condescending insults!” Well this is indeed an interesting reflection.
Myco spore germination is inhibited by high available P levels. But there are commercial myco products out there comprised of strains that have the ability to handle P. Some types can only handle available P at 20ppm so they are no good for hydroponics. There are other species that do well from 70-100 ppm during spore germination and can then can handle up to 300ppm.
PS those studies below are 20 years old. There is lots more recent info that shows a range of P response.
There ya go lads – twisting the facts. I note you edited me when discussing Urban Garden is owned and run by {DELETED} and Advanced Nutrients (who sell growers mychorrizae for use in Hydroponics). Actaully let me correct the detractor on the 20ppm of P and state that VAM nutrients should contain about 10ppm of P. Here’s another piece of research – I’m happy to post loads more. Jesus, Noam Chomsky would have a firld day with this one —– hydro companies manufacturing consent.
Abstract (H.-J. Hawkins and E. George)
Linum usitatissimum, Sorghum bicolor and Triticum aestivum plants were further colonised by the arbuscular mycorrhizal fungus, Glomus mosseae, during a four week period of hydroponic culture after a pre-culture period of three weeks with the fungus in perlite substrate. The viability of mycorrhizal colonisation of T. aestivum was indicated by an initial experiment where G. mosseae from mycorrhizal plants colonised non-mycorrhizal plants when the plants were grown together in the same hydroponic container using modified Long Ashton nutrient solution. Intermittant aeration of the plant roots (2 h periods, four times per day) provided a compromise between adequate aeration and minimal disturbance of the fungus. In a second experiment, two nutrient media, modified Long Ashton and modified Knop plus Hoagland medium were compared for culturing G. mosseae on T. aestivum. A significantly higher root dry weight was found for the mycorrhizal versus the non-mycorrhizal wheat plants in modified Long Ashton nutrient medium, which contained 10 µM P and an organic buffer. Modified Knop plus Hoagland nutrient medium contained a high P concentration (0.9 mM) and did not produce viable cultures of mycorrhizal colonisation. In a third experiment, modified Long Ashton medium was used for hydroponic culture of mycorrhizal L. usitatissimum, S. bicolor and T. aestivum. The root colonisation percentages for T. aestivum (73%), S. bicolor (36%) and L. usitatissimum (65%) were within the range of colonisation rates obtained with solid substrate culture in perlite. Viability of the mycorrhizal structures in hydroponic culture was assessed by monitoring activity of fungal succinate dehydrogenase and found to be similar to cultures in perlite. No difference in the P concentration of mycorrhizal and non-mycorrhizal plants was observed, possibly owing to the lack of diffusion limits for P in hydroponic solution. This report describes a system for the viable culture of G. mosseae with different plant species where a high mycorrhizal colonisation rate was produced under conditions of a short culture period using intermittent aeration, a low concentration of P supply and an organic buffer.
Eyup Jimboon,
Thanks for posting up further research on Mycorrhizae in high P levels. And please keep it coming—it’s fascinating. We are in touch with Dr. Michael Amaranthus, the author of the article, and will be posting up other research papers shortly.
Now then, a polite word in your ear, albeit on a public forum (as you continually make up email addresses we have no other choice!) We are not pushing a mycorrhizae-based commercial agenda. And we are not run by any nutrient or hydroponic wholesale company. The whole point of Urban Garden Mag is that it’s written by growers, for growers. Yes, we all have our friends in the industry. That’s life. That’s human. But we’re not “run” by some shadowy bosses, “manufacturing consent” as you put it. Hey Jimboon, if you want to write a counter article, we’d definitely consider it for publication. You’re clearly well read on the subject. So how about that?
The whole point of the article was to ask the question “Do Mycorrhizae have a role in Hydroponics?” and we cite that some nutrient companies say YES and some say NO. There is evidence that certain strains of Mycorrhizae are more tolerant of high P levels than others. The article also serves to demonstrate the role of mycorrhizae in general.
If you really believe that we get up in the morning to push the agendas of certain parts of the industry then … well, the politest thing we can say is that you grossly underestimate us. But at least give us a chance to prove otherwise.
Respect for placing up my posts which at least demonstrates a willingness to post peer reviewed information that counters your own.
Sure guys when your experts present their research which is peer reviewed I’ll look forward to seeing it.