The Orchid Forum, for the UK and Europe (previously known as The UK Orchid Forum) • View topic - Mycorrhizal Fungi
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 Post subject: Mycorrhizal Fungi
PostPosted: Sat Jan 11, 2014 11:47 pm 
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I live in: United Kingdom (Wales)
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I am confused about the role of mycorrhizal fungi in orchid growth.
As all our orchids start their lives in sterile conditions either as seeds or meristem cells ,do our mature orchids have a relationship with mycorrhizal fungi ?
If they do does it arrives via airborne spores ?
Do different species / orders of orchid associate with different species of fungi?
Has anyone had any success sowing seed on mature orchid media/roots ?
I hope someone can answer some of my questions or point me in the direction of where I can find more information.
Thanks
Terry


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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Sun Jan 12, 2014 10:01 am 
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Hi Terry,

Your question is a great one.

Mycorrhizal fungi association is only important nowadays in orchids growing in the wild. The fungi needs to 'invade' the orchid seed, and it is in fact a very fine line between an association and a fight for life, in fact. The fungi tries to overtake the seed, but the sugars they make as a by product feed the seed's embryo; as the embryo starts to develop and grow, it produces some sort of inhibitor to keep the fungi at bay, so it is not really a symbiosis relationship in the full context of the word as you can see (where both organisms benefit from each other, as opposed to trying to overtake each other). I forget the full implications of the relationship, but I remember it was something like that.

For orchids grown in sterile conditions, the fungi is skipped altogether, as the sugars and nutrients in the agar solution provide the seed's embryo with the food it needs to get kick started. Spreading seed on a pot with a mature orchid will not help, since the fungi was never there to begin with!

I have seen one occasion at least where a seed pod ripped and spread the seed on the roots of a mature Phalaenopsis gigantean which was mounted. This orchid was indeed wild collected and so, the fungus was present on the roots. The result was a few years later hundreds of seedlings growing on the mount and amongst the mother plant roots. This won't be happening with our orchids though, as collection and trade of wild orchids is strictly forbidden now.

I am sure this is not 100% correct, so I hope someone else chimes in to put whatever wrong information I have given right (sorry, just woken up and coffee has not kicked in yet).

Francis

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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Sun Jan 12, 2014 11:20 am 
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That all looks like good information to me Francis :D
I have tried a Mycorrhizal fungi in soil I am planting hardy orchids direct into the garden and have also done this with pots in the hopes I get better growing results.
Some people say you cannot grow a hardy orchid without the fungi some say you can. I have had success both with both types of plantings.
I have found over the years not to use it with seedlings I am planting out, but once in the soil if you allow an adult plant to seed naturally you do get seedlings .... eventually

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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Tue Jan 14, 2014 7:41 am 
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Terry wrote:
Has anyone had any success sowing seed on mature orchid media/roots ?


Most of the first hybrids were grown from seed sown on the surface of the potting medium that the parent was growing in. As far as I have been able to discover the first seedlings grown in vitro date from around 1907.

The Australian Enamel orchids are dependent on their mycorrhizal fungi not only for germination but also throughout their lives. They will only grow where their symbiotes live but the two have been persuaded to grow together in containers. Unfortunately the fungi are short lived in containers, normally dying during the heat of summer. The orchid dies shortly thereafter.

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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Tue Jan 14, 2014 8:58 pm 
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A very old fashioned method of raising orchids from seed was to sow on fine muslin stretched over a dome of live sphagnum in a clay pan, kept moist under a bell jar. Unlikely as it may seem this does work (sometimes), and to my surprise I managed to raise a bunch of Epidendrum ibaguense seedlings from a selfed flower a few years ago.


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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Tue Jan 14, 2014 11:15 pm 
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Thanks for your replies.
On an American forum I read a thread about seeds germinating on the bark of trees which had been used to mount orchids.
The seeds germinated within half an inch of the orchid roots.
The conclusion seemed to be that the orchid seeds did not need a specific fungus from their native habitat but could make use of fungus that was available around them.
I think I'd like to try the muslin sphagnum method but I'll need to fertilize a few flowers and grow a seed pod first.
When a plant is producing a seed pod will it still produce a flower spike the next year ?
Thanks again
Terry


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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Wed Jan 15, 2014 12:25 am 
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Tanis wrote:
That all looks like good information to me Francis :D
I have tried a Mycorrhizal fungi in soil I am planting hardy orchids direct into the garden and have also done this with pots in the hopes I get better growing results.
Some people say you cannot grow a hardy orchid without the fungi some say you can. I have had success both with both types of plantings.
I have found over the years not to use it with seedlings I am planting out, but once in the soil if you allow an adult plant to seed naturally you do get seedlings .... eventually

Most of the hardy orchids that I grow have never seen a fungus and grow perfectly well without. They are commercially raised plants with no need for fungus.
Others refuse to germinate asymbiotically but the mature plants do not need fungus and so they grow well in cultivation.
But I am coming to the conclusion, based on twenty years of growing, that some commonly grown plants rely on fungus far more throughout their lives. For instance Dactylorhizas seed all over the place in my greenhouse, very often in mature pots of bletillas or hostas where the fungi have obviously developed. But when I try to move these seedlings into the same type of compost that their parents were growing in, they very often die. I believe these plants still need the fungus. I have a pot of dactylorhiza seedlings, 100 plus plants, now at least three years old, that I found when I was about to repot the parent plant. I have left them in the original compost and so far so good. But there will come a time when their size demands that they are moved on and although I plan to seed the new compost with the the old, I suspect that some will die.
I suspect this may be why wild dug plants are said to be difficult in cultivation.
And twenty years of spreading seed of dozens of orchid species around my garden has produced a total
of NIL orchids. I know we have lots of slugs and the soil is unsuitable for many of the species, but I think the main reason is the absence of the right fungi.


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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Wed Jan 15, 2014 10:27 pm 
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It was a Dactylorhiza (I think praetermissa) that got me interested in orchids.
About 14 years ago a colliery waste tip near me was landscaped by the local council.The colliery waste has compacted so much it acts like concrete and allows no water through. About nine inches to a foot of soil covers the waste and even though drains were laid in the ground it is very wet for most of the year. About 8 years ago I noticed a Southern Marsh Orchid( I think they are Southern Marsh) and when I searched I found 4 other flower spikes.
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That year and every year since just as the flowers are fully open and looking their best the council comes along with a tractor and lawnmower and shreds them . I have persuaded them on a few occasions to leave the grass uncut where some of the orchids are but a few weeks later the next man with a mower comes along gets them.
All this would be very depressing except for the fact that the orchids are thriving on this treatment. They have increased and spread every year and this spring I counted 170 flower spikes. Some of this increase has occurred by the psudobulbs multiplying resulting in three flower spikes where there was only one a few years ago. In the early years none of the flowers survived long enough to produce mature dry seed pods . Now they have spread and 5 or 6 are growing out of reach of the man with the mower and produced dry seed pods last year. Some of the newer plants are 20 to 50 meters from the original plants and I was wondering how they got there .
With the fleshy flower spike could these be cut by the mower and form new plants much like a cutting does ?
Could viable seed develop after a spike has been cut using the resources of the flower stem ?
I did keep a few flower spikes which had been cut alive in a glass of water for a good number of weeks the result of which has been 8 years of my indoor orchids hiding the orchid aphid Aulacorthum circumflexum which is nowhere to be seen for months until a flower opens and overnight they are all over it.
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I scattered last years seeds around the village anywhere with damp grass ,this year I'll try some into pots, hopefully with a bit of fungus from around the adult plants .

Terry


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 Post subject: Re: Mycorrhizal Fungi
PostPosted: Thu Jan 16, 2014 12:16 am 
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Once the top growth is cut off it cannot be used as a cutting and I doubt that the seed will develop as this takes some time.
However the new tubers below ground may have developed far enough to survive by the time of flowering and as you say they can treble each year.
As for the spreading you must remember that orchid seed is so very light that it can travel miles on the wind and each seed pod contains thousands of seeds. This is why orchids are so good at colonising old industrial sites, although their presence may be short lived unless the site is managed correctly as they are often out competed by more vigourous growing plants.
One of my local meadows housed thousands of Dactylorhizas only four years ago, but two wet summers saw an explosion of meadowsweet which now dominates with the orchids surviving only in a few areas.
In a nearby field grazing has been stopped for two years and already there are hundreds of praetermissa and thousands of common spotted (fuchsii) which must have been present before but were being grazed off before flowering.


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