Where are the mycorrhiza hiding?

transcript of seminar at Coed Nant Gain with Bruce Ing July 2006

All trees have mycorrhiza, but the one we are looking for particularly is the ecto-mycorrhiza, which is where the fungus threads are on the outside of the root, forming a sheath.  Most forest trees, like oaks, conifers, beech, birch and things like that, have ecto-mycorrhiza and they are associated with toadstools.
The trees like sycamore and ash, and a few others, don’t have ecto-mycorrhiza.  They have an internal, microscopic mycorrhizal system called an arbuscula mycorrhiza system, and these are very tiny, very simple fungi which don’t ever produce a fruit body visible above the ground.  So you don’t get a lot of these nice fungi in ash woods.  You get litter fungi in ash woods, which are good, but you don’t get mycorrhizal. 
So oak, beech, birch, conifers, ash, willows to some extent, poplars, but in general conifers are very good and they tend to be fairly specific, some of these fungi as well, so you get oak mycorrhiza, and beech mycorrhiza
The fungi have been introduced with the trees. Larch for example isn’t a native, so the fungi aren’t native either, but they’ve established, so we allow them as British. Mycorrhizal fungi have a very different physiology from non-mycorrhizal fungi.  They are very much more sensitive, and they are also capable of picking up radio nuclides and heavy metals, far more effectively than the non-mycorrhizal.

Birch is a pioneer tree, and one of the reasons why it is so successful is that it can form mycorrhiza with a very wide range of toadstools, and indeed with some other fungi too, so it will take the same toadstools that will grow with oak or with pine, as well as some of its own special ones, so there’s a very large number of species, probably more than any other native tree, that will associate with birch.  It grows in a very wide range of habitats where it will meet a lot of different fungi, and it seems to be very neighbourly, and will grow with practically anything it meets, and that accounts for its success, and also why birch woods are very rich in fungi. 
We find mycorrhizal swellings on the birch roots which are growing in litter which is predominantly beech.  The fungi are feeding on the beech litter, and passing the nutrients directly to the roots of the tree via the mycorrhizal connection.   And we have a nice, soft , uncompacted litter here, which is better for the fungal growth.   Where we were looking before we were on the edges of paths.  It was hard.  This is also moist, so everything here is better than where we looked before.
(Here we have) an active, developing mycorrhizal system and sometimes its bright pink, so is very, very clear.  The first bit we found was slightly reddish, and that was older, but was probably pink or white to start with, and it just takes up the tannins and so on from the litter, particularly the beech-leaf litter, which is very rich in tannins.

As the young root tips grow out, so the fresh mycorrhiza grows along the root tip, and further back along the root, the sheath becomes much less obvious, although it’s still there, probably it isn’t functioning too well because only the root-tip is really absorptive, and so you get mostly this mycorrhiza right on the very ends of the young roots.  And then they slowly become less obvious as the root ages.  We talk about months, rather than years.  So, you have to find feeding roots.          (Recording ends)

Transcript from tape kindly provided by Brian Burnett

Mycorrhiza in
the root system

Enlarged mycorrhiza (on the camera case) clearly seen is the white tips