Wednesday, October 18, 2006

Mycorrhyzae help plants survive heavy metals/salt

[Updated Oct. 27]

It seems like the more we learn about mycelium, the more we learn how beneficial it is to all sorts of life. Research published in the African Journal of Biotechnology (on the Mycorrhyza Literature Exchange site) shows that mycorrhyzae can help plants survive higher levels of zinc and cadmium:
...From a number of physiological indices measured in this study, microsymbionts significantly increased dry weight, root : shoot ratios, leaf number and area, plant length, leaf pigments, total carbohydrates, N and P content of infected plants as compared with non infected controls at all levels of heavy metal concentrations. Tolerance index of cowpea plants was increased in the presence of microsymbionts than in their absence in polluted soil. Microsymbionts dependencies of cowpea plants tended to be increased at higher levels of Zn and Cd in polluted soil. Metals accumulated by microsymbionts-infected cowpea plant were mostly distributed in root tissues, suggesting that an exclusion strategy for metal tolerance widely exists in them.


This news from Scientia Horticulturae (also on the Mycorrhyza Literature Exchange site) shows that mycorrhyzae can benefit tomatoes grown in saline conditions:
This study was conducted to determine if pre-inoculation of transplants with arbuscular mycorrhizal (AM) fungi alleviates salt effects on growth and yield of tomato (Lycopersicon esculentum Mill. Cv. Marriha) when irrigated with saline water. Tomato seeds were sown in polystyrene trays with 20 cm(3) cells and treated with AM fungi (AM) or without (nonAM) Glomus mosseae. Once the seedlings were reached appropriate size, they were transplanted into nonsterile soil in concrete blocks (1.6 m x 3 m x 0.75 m) under greenhouse conditions. The soil electrical conductivity (ECe) was 1.4 dS m(-1). Plants were irrigated with nonsaline water (ECw = 0.5 dS m(-1)) or saline water (ECw = 2.4 dS m(-1)) until harvest. These treatments resulted with soil EC at harvest 1.7 and 4.4 dS m(-1) for nonsaline and saline water treatments, respectively. Root colonization with AM fungi at flowering was lower under saline than nonsaline conditions. Pre-inoculated tomato plants with AM fungi irrigated with both saline and nonsaline water had greater shoot and root dry matter (DM) yield and fruit fresh yield than nonAM plants. The enhancement in fruit fresh yield due to AM fungi inoculation was 29% under nonsaline and 60% under saline water conditions. Shoot contents of P, K, Zn, Cu, and Fe were hi-her in AM compared with nonAM plants grown under nonsaline and saline water conditions. Shoot Na concentrations were lower in AM than nonAM plants grown under saline water conditions. Results indicate that pre-inoculation of tomato transplants with AM fungi improved yield and can help alleviate deleterious effects of salt stress on crop yield.


Update: As discussed elsewhere on these pages, Glomus mosseae helps plants resist the uptake of arsenic and thereby increase the uptake of phosphorus. Glomus mosseae has also been shown to reduce the uptake of copper, zinc, lead and cadmium.
A glasshouse pot experiment was conducted to investigate effects of the arbuscular mycorrhizal fungus Glomus mosseae on the growth of Vicia faba and toxicity induced by heavy metals (HMs) (Cu, Zn, Pb and Cd) in a field soil contaminated by a mixture of these metals. There was also uninoculation treatment (NM) simultaneously. Mycorrhizal (GM) plants have significantly increased growth and tolerance to toxicity induced by heavy metals compared with NM plants. P uptake was significantly increased in GM plants. Mycorrhizal symbiosis reduced the transportation of IlMs from root to shoot by immobilizing HMs in the mycorrhizal, shown by increasing the ratios of HMs from root to shoot. Oxidative stress, which can induce DNA damage, is an important mechanism of heavy metal toxicity. GM treatment decreased oxidative stress by intricating antioxidative systems such as peroxidases and non-enzymic systems including soluble protein. The DNA damage induced by heavy metals was detected using comet assay, which showed DNA damage in the plants was decreased by the GM treatment. [Journal of Environmental Sciences-China also see University of Ljubljana]
Oyster mushrooms, a type of saprophytic mushroom (not mycorrhizal), have been used to detoxify soils contaminated with cadmium. However, these mushrooms would not be fit for human consumption. When using mycelium to detoxify land or help plants resist toxins, do not eat any mushrooms that fruit.

5 comments:

PeakEngineer said...

Do you know what the methods are for extracting mycelium, or what sort of soil carries it?

DJEB said...

I should do this in a full-blown feature, but until then, one mini course in simple mycelium propagation coming up:

First thing to note is that any reasonable healthy temperate soil will contain a lot of mycelium. If you are walking in a forest with healthy soils (little acid rain damage, etc.) each footstep will have up to 4800km (3000 miles) of fungal hyphae under it! Then there are spores. Spores are everywhere - everywhere. They will survive a vacuum so there are some viable spores that have been drug up into orbit on space missions. If you have a substrate and water, sooner or later saprophytic (decomposing) fungi are going to take advantage of it (if actinomycetes don't beat them to the punch).

So, if you set up the conditions for fungi, they will show up on their own.

As for soils that carry mycelium, forest soils are the best souce. Prairie soil tends to be more bacterial-based, and desert soils are entirely bacterial based soils. Even in deserts, however, if you set up the right conditions for fungi, they will grow.

When building gardens, I always dig up a few cups of healthy forest soil (ideally from different locaions) and dump it into the garden and cover it with mulch.

Fungi Perfecti sells mycorrhizal fungi spores that can either be spread over a planting area or added to water for young plants to be dipped in. Simple.

But if you want fungi that you can use for food or medicine, you will have to cultivate it. The useful variety are unlikely to show up on their own, and many deadly species are likely to show up.

The following is general cultivation information that is mostly applicable to saprophytic mushrooms, not the mycorrhyzal ones featured in the article.

The easiest way is to transplant wild patches:

1) Dig up a sample of wild mycelium and place it in a paper bag to keep it from drying out.

2) Site a moist, shaded patch or create one.

3) prepare a thick bed of woodchips (fast-growing deciduous wood is best, no eucalyptus - it can make yo ill) or straw (straw works better pasturised - put a burner under a steel drum that never had chemicals in it and cook the straw at 71C for 2 hours). Other substrates like paper waste (printed with soy ink), okara (by-product of tofu making) or cork cobs and stalks work well. Make the bed about 30cm (12") deep. Adding rice bran or spent grain from brewing makes a good supplement in moderation as it will attract bacteria, too.

4) Water the substrate.

5) Rake in the spawn at rates of 1 part spawn and 4 or 5 parts substrate. (You can see how using commercial spawn gets expensive).

6) Water it again.

Inoculating with cultured spawn would be the next fastest and easiest way. You can get spawn ready to use from Fungi Perfecti.

For this technique you would:

1) Find a moist, shaded area for cultivation (or create one).

2) Early spring of early fall are the best times for inoculation.

3) Prepare the substrate as above.

4) Water the substrate.

5) Rake in the spawn.

6) Water it again.


The technique of Spore-mass inoculation is much cheaper, but requires more involvement on your part:

1) Harvest mushrooms - 25% of what you see in a patch makes for a sustainable harvet.

2) Skip to step 3) or make spore prints by placing the mushrooms gills down on a clear sheet of paper. The spores will fall on the paper and collect there.

3) Place the spores in a 20l (5 gallon) pail of non-chlorinated water. Add 2g of salt, 50ml of molasses. Add the mushrooms or the spores. Let sit 24 to 48 hours at 10C to 26.7C.

4) Spread the slurry on the substrate as outlined above.

DJEB said...

Forgot one thing...

If you are using the spore-mass slury and putting muushrooms directly in the bucket, take them out after 4 hours.

Nathan Edwards said...

Djeb, Nathan here in Melbourne. I have found your blog and website a great source of info. Was wondering if I could print out the Passive heating/ cooling pdf to give to a client for their perusal. I will make sure to credit you if it's cool. Just did my PDC with Mollison and Lawton it was great. Love your work, if you are ever in Melbourne drop me a line

DJEB said...

Hi Nathan. I've heard of you from an email from Geoff. You are welcome to our information. I'm glad it helps.

If you need to get in touch, you can reach me at dbarnes(at)ecoedge.ca