UKTC Archive

RE: Ganoderma applanatum/australe on n.maple - implications

Subject: RE: Ganoderma applanatum/australe on n.maple - implications
From: Viper Snake
Date: Dec 24 2011 15:34:23

 
Dear Luke & David,
 
I add some final remarks to the answers of David to the questions of Luke.
 
1. Secondary metabolites: I agree that any work involving wood blocks (as 
opposed to living trees) would fail to take account of the possibility of 
defensive substances being transported in order to strengthen reaction zones. 
You've touched on a long-standing controversy: are reaction zones just formed 
"once and for all", or are they maintained by a supply of sugars, which could 
be converted in additional phenolic and other defensive materials?

1. From the side of the necrotrophic parasitic or saprotrophic wood degrading 
macrofungi living in the heartwood of trees, there also has been some 
defensive reaction documented in forming barriers close to the living tissues 
to shield off the mycelia and prevent them from being attacked by defensive 
or toxic substances produced and secreted by the tree.
In this way, Laetiporus sulphureus can completely brown rot the heart wood of 
Quercus robur, which is part of the survival strategy of both the fungus and 
the (veteran) tree.
And Armillaria species shield off their vulnerable dead wood decomposing 
hyphae with melanine plaques and surround their hyphae inside rhizomorphs 
with a melanine layer, that protects the hyphae against attacks of toxins or 
acids (Quercus robur/petrea, Castanea sativa) produced by the living tissues 
of the tree.
 
2. Moisture content as a passive defence: Others, having colonised a volume 
of wood, can pump excess water away. It's obvious that their fruit bodies can 
provide an exit-route, either by evaporation or by active exudation of water 
(as in the well-known case of various Inonotus species).
 
2. A phenomenon (guttation) also known from Laetiporus sulphureus, 
Oligoporus/Tyromyces species, Heterobasidion annosum and Fomitopsis pinicola. 
And the dry brown rot causing Serpula lacrymans is capable of transporting 
moisture, which is set free at one spot while decomposing wood, to a dry spot 
elswhere by its rhizomorph strains.
 
3. the patterns of fungal colonisation and fruiting around the bases of trees.
 
3. The law of using the way of least resistance to fruit is also responsible 
for the presence of fruitbodies in between the buttresses at the base.
 
4. In some cases, it looks as though decay stops when the fungus runs out of 
available wood as its energy-source. Otherwise, the fungus survives either by 
being able to move into fresh sapwood (arguably as a parasite) or by taking 
advantage of the natural aging of sapwood. As you rightly point out, the 
formation of new increments by the tree can often keep pace with the outward 
extension of the fungus. I think, therefore that we should not assume that a 
modest amount of 'parasitic' colonisation by the fungus is a problem for the 
tree.
 
4. Of which Fistulina hepatica is an example, as it first "feeds" on tannin 
or vinegar acids produced by the sapwood of the tree (Quercus robur/petrea, 
Castanea sativa) in defense, without causing a problem to the stability of 
the tree, because after the mycelium finally enters the cambium and causes a 
necrosis of living tissues and bark from which exposed (dead) sapwood it 
fruits, the tree compensates for the loss of stability in a tree species 
specific way (see : 
http://arbtalk.co.uk/forum/members/fungus-albums-fistulina-hepatica.html ), 
which is a good example of co-evolution between fungus and tree species.
 
Kindest regards too,
Gerrit
 
 
 
1. In the experiments described the blocks of wood were excised from trees 
and therefore what occurred in them was not influenced by the rest of the 
tree. Could it be possible that a tree could mobilise secondary metabolites, 
manufactured in other parts, to arrest fungal growth? It would be interesting 
to know whether fungistatic and/or fungitoxic chemicals could be transported 
in xylem and/or phloem sap, the symplast or a combination of these. How could 
we find out whether this is a possibility and, if it is, its significance?
 
2. Boddy and Raynor (1983) 
(http://onlinelibrary.wiley.com/doi/10.1111/j.1469-8137.1983.tb04871.x/abstract)
 proposed that the saturated nature of live sapwood would prevent development 
of decay fungi within it. Could it be possible that once Ganoderma adspersum 
had penetrated the reaction zone further growth would be arrested, or at 
least slowed, by the saturated nature of the substrate? Could it potentially 
enter 'hibernation' until the wood becomes aerated? This would create a 
situation where it would be 'first on the scene' after the wood becomes 
aerated or physiologically dysfunctional - a similar strategy to fungi that 
are latent within live trees until they lose vitality. 

3. Would the fact that the wood blocks were excised from the tree also affect 
the energy status of live sapwood cells? Could, during the life of the 
experiment, their carbohydrate reserves become depleted by respiration and, 
if so, could this affect the ability of the wood behind the reaction zone to 
take defensive action and therefore the weight of the blocks at the end of 
the experiment?

Finally, I tend to assume that the majority, if not all, the Ganoderma 
brackets that we see in the UK on live beech trees are those of G. adspersum. 
These are usually in the flutings between buttresses. I've previously assumed 
that the growth of hyphae from a centrally occupied area in a tree, towards 
the outside, was primarily to produce the brackets and was confined to the 
dead, moribund or slowly growing sapwood found in these areas - they are 
rarely seen on healthy buttresses that are growing rapidly. I mused that wood 
in these compressed flutings may have died, become moribund or that the 
hyphae were growing between the two faces of bark. I also presumed that the 
growth of fungal hyphae in these areas was primarily to produce fruit bodies 
rather than obtain additional substrate to digest. Do others consider that 
there may be some validity with these assumptions? Maybe we need to create a 
bank of photographs of recently felled tree stumps with brackets on them and 
compare these observations. 

If fungal hyphae are restricted to dead or moribund tissues in flutings, and 
don't have the capacity to aggressively colonise healthy sapwood while the 
tree remains healthy, should it not be the case, bearing in mind the axiom of 
uniform stress, that the tree will allocate sufficient resources to growing 
additional tissue around colonised areas to compensate for the reduced 
mechanical strength of the decayed wood (sorry, that sentence is a bit of a 
mouthful!). That is until it loses vitality? If this were to be the case the 
decay fungi and healthy tree could live together for many years or decades 
until the tree suffered an event that severed/killed roots, severed/killed 
crown area or sapwood. In the Lake District, my observations suggest that 
drought and storm damage are the weather events that most often create 
physiologically dysfunctional sapwood that becomes available for colonisation 
by decay fungi.

Please accept my apologies if I'm rambling. 

Merry Christmas to one and all.

Luke



-----Original Message-----
From: David Lonsdale [mailto:d.lonsdale2@xxxxxxxxxxx.com] 
Sent: 21 December 2011 18:30
To: UK Tree Care
Subject: RE: Ganoderma applanatum/australe on n.maple - implications

Dear Gerritt,

In answer to your question, I define the relevant terms as follows:

1. Biotrophic parasite: a parasite which obtains its nutrients from the 
living cells of the host (usually by the penetration of those cells, 
without killing them). Examples include rusts and mildews.

2. Necrotrophic parasite: a parasite which obtains its nutrients by killing 
cells of the host (usually by the secretion of enzymes and/or toxins). 
These parasites are usually able to grow also as saprotrophs (4, below) and 
they are therefore often alternatively called "facultative parasites". 
Examples include many fungi and bacteria that cause general dieback and/or 
decay of host tissue.

3. Hemibiotrophic parasite: a parasite which obtains its nutrients both as 
a biotroph (usually when it first penetrates host tissue) and as a nectroph 
(usually at a later stage, after an initial biotrophic phase). Examples 
include many organisms that cause leaf spot diseases.

4. Saprotroph: an organism which obtains its nutrients from the dead 
remains of one or more living organisms.

As far as I know, there are no wood decay fungi in categories (1) or (3) 
above. Some of them have the ability to grow into previously living 
sapwood, causing it to die (or become "dysfunctional" and then causing 
decay. I think that they can be regarded as necrotrophic parasites (2), but 
I do not like to use this term without qualification, since many of them 
live predominantly on wood that is already dead. This could be sapwood that 
has been damaged by injury, or it could be central wood or the tree, which 
has become heartwood or ripewood because of aging. 

Traditionally, wood decay fungi have been described as "parasitic" if they 
are found on living stems, branches or roots. I do not think that this is 
correct if the fungus concerned is colonising only wood that is already 
dead.

According to the above definitions, Ganoderma applanatum has been observed 
to be mostly saprotrophic, whereas G. adpsersum/australe has some capacity 
to act as a necrotrophic parasite. These observation seem to be confirmed 
by some experimental work by my friends Schwarze & Ferner at the University 
of Freiburg i. Br., Germany. (see: 
http://www.enspec.com/articles/ENSPEC%20Research%20Paper%20-%20Ganoderma%20on%20Trees.pdf
 )

Schwarze & Ferner found that G. adpsersum/australe was able to penetrate 
defensive barriers (reaction zones), thus growing into functional sapwood. 
It does not necessarily harm the tree seriously. Instead, it might be able 
to co-exist with the tree for many years, instead of dying out when it has 
utilised all the wood that was initially available to it. In some cases, 
however, the fungus does enough damage to the sapwood (especially in the 
roots of the tree) to cause the decline and perhaps death of the tree. 
Also, the decay can, in my experience, become overwhelmingly rapid if the 
wood becomes more aerated because of excessive pruning or the 
storm-breakage of major branches. 

As suggested in the recent correspondence, G. adpsersum/australe appears to 
behave differently in different host species. I think that it can be 
especially aggressive in species with which it has not co-evolved. I have 
seen examples where G. adspsersum/australe (or perhaps a similar-looking 
species of Ganoderma) seems to have killed exotic conifers such as 
Araucaria araucana. I agree that it can cause extensive decay in the 
broadleaved trees in your list. However, in Fagus sylvatica (one of its 
main hosts in the UK), the tree and the fungus often seem to co-exist for 
many years. The co-existence is probably even longer in species like 
Quercus robur and Q. petraea, which have durable heartwood and therefore 
tend to become decayed more slowly.

Regards,
David

-----Original Message-----
From: Viper Snake [mailto:snake24@xxxxx.nl]
Sent: 21 December 2011 14:14
To: UK Tree Care
Subject: RE: Ganoderma applanatum/australe on n.maple - implications




David,

1). Tony Croft has been using the term 'biotrophic parasite' in relation to 
G. adspersum/australe on here. I questioned him about these labels and 
asked him whether he could point me to any research that demonstrated that 
the fungus was 'biotrophic' and/or 'parasitic', because this was news to 
me, but he hasn't replied yet. Can you point me in the right direction?

1). Tony uses my terms and the results of my in situ research on biotrophic 
and/or necrotrophic parasites, which I already have explained on Arbtalk, 
see : 2. http://arbtalk.co.uk/forum/529703-post53.html .

2). Similarly, that G. adspersum/australe is deterministically fatal to 
Acers, no matter the circumstances, is also news to me. Where does the 
research for this conclusion come from ? 


2). From my own field research on the effects on the stability and 
condition of different deciduous tree species of the biotrophic parasitic 
G. australe, of which the mycelium causes a white rot with selective 
delignification, that is most detrimental to Acer, Platanus, Populus, 
Salix, Tilia, Aesculus (Anne Frank tree) and Quercus rubra.

Gerrit





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