Why does.................?

[Amelanchier]

Interesting. Different niches exploited and different evolutionary paths followed i suppose. Willow and Poplars also have Stomata on the upper surface of their leaves.

 

The stomata on the upper surface of leaves generally have much smaller appatures than stomata on the underside of leaves and species like Ouercus robur have many more stomata of larger appeture on their leaves than common lime.

 

It may have some advantage in allowing more efficient cooling allowing leaves to stay more photosynthetically active in the scorching mid day sun, provided there is enough water available.

 

I would think that stomata on the underside of the leaf loose water at a slower rate to those on the upper surface it may be an advantage for trees such as willow to draw up large amounts of water quickly to modify there soil environment.

 

Maybe this helps Willows, Limes, Poplars to loose less functional xylem tissue when heavily reduced compared with species such as Oak where greater amounts of foliage are required to maintain functional xylem.

 

Perhaps as water is used for photosynthesis, those species that expolited wet ground niches could afford to be wasteful with it? I have a picture in my head of 50's american muscle cars - very fast but wasteful on 'fuel' 'cos in the culture that 'evolved' them, fuel was plentiful.

[gibbon]

 

Maybe this helps Willows, Limes, Poplars to loose less functional xylem tissue when heavily reduced compared with species such as Oak where greater amounts of foliage are required to maintain functional xylem.

 

I thought these species loose more functional xylem when heavily reduced? I would consider these 3 species to be poor compartmentaliser of decay. Any any heavy reduction I would expect to see a greater loss in functional xylem.

 

I was wandering whether it has anything to due with these species being difuse porus. Do difuse porus trees generally have a higher water demand?

 

As you get closer to the tropics tree species tend to become more diffuse porus . Many tropical trees and Eucalyptus have stoma on the upper surface and just like Poplars tend to dip their leaves away from the sun at mid day to reduce photosythethis and transipiration because they are unable to close stoma.

 

I have an idea that by having more stomata which do not close, transipiration will continue to some degree all day which may help prevent water columns from breaking and becoming filled with air if stomata were to close at mid day. This would be especially important for tall trees where the stress on the water column is greatest.

 

Also you mentioned that some species might be trying to modify their soil environment. If these species are known to thrive in wet soil, modifying the environment would improve conditions for other species and increase competition.

 

I could be barking up the wrong tree but these were my thoughts.

[David Humphries]

Good ponderings amigos

 

Feel free to add your own Tbq's, btw

 

Not closing Tbq 1, as I'm sure there is much, much more to add,

 

however Tbq number 2;

 

Why does..................endophytic mycorrhyza not produce fruiting bodies, whereas ectophytic do?

 

 

 

 

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[Dean Lofthouse]

Why does..................endophytic mycorrhyza not produce fruiting bodies, whereas ectophytic do?

 

 

 

 

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Perhaps lack of light ???

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

I haven't got the foggiest what I'm talking about.

 

Endo (inside) ??

 

Ecto (outside) ???

[Will Hinchliffe]

Nice post Gibbon.

 

Modifying the soil environment would improve site conditions for other species, but if you think about succsesion on a lake with a very wet edge the willows might be colonising more and more of the marshy land as they dry it out and other species colonising the land that has been dried out by the willows.

 

Tbq number 2

 

Endomychorrhizal associations are formed by fungi belonging to the order Glomerales, ectomychorrizal fungi belong are either Ascomycytes or Basidiomycetes. The Glomerales are an ancient group of fungi and form associations with almost every plant and are not host specific. Some do form macroscopic fruiting bodies but this is very rare. The fungi are incapable of living without a host (obligatly symbiotic). They do produce spores and these can be found in almost all soils. There is a suggestion that they lack some of the genetic material for growth and reproduction and that this is suplied by the host plant.

 

Fungi, Brian Spooner and Peter Robertsm (excellent book) - refers to them as Vesicular-Arbuscular Mycorrhiza (VAM)

 

I dont think they produce fruiting bodies because they have no need for airborne spores because they are everywhere already.

 

It is thought that Endomychorrhal fungi played an important role in the colonisation of land by plants, they are that old!! (400 million years).

[Dean Lofthouse]

Cutting and pasting not allowed Phenom you'll get down marked by David !!

[Will Hinchliffe]

Cutting and pasting not allowed Phenom you'll get down marked by David !!

 

How very dare you. :001_tongue:That is an simplified interpretation of someone elses work that I have clearly referenced and added my own thoughts to at the end:closedeyes:

[gibbon]

Ok Boffins. Why don't we see hundreds of Apple trees growing on roadside verges?

 

I often chomp an apple on my travels and throw the core out the window. I recon this has been going on for thousands of years and millions of apple seeds have ended up on banks and verges. Why aren't our country roads lined with apple trees?

[Dean Lofthouse]

Ok Boffins. Why don't we see hundreds of Apple trees growing on roadside verges?

 

I often chomp an apple on my travels and throw the core out the window. I recon this has been going on for thousands of years and millions of apple seeds have ended up on banks and verges. Why aren't our country roads lined with apple trees?

 

Nature intended the seed to pass through the gut of an animal which helps to start the seed off ?

 

Perhaps if we eat the cores then "pass" the seeds roadside they may germinate better, if not you could end up just getting arrested alot

[David oakman]

I think you will find apple does not germinate very well thats why they graft alot. Dean you are correct go to the top of the class:001_smile: I am now about to start cutting some hay which is full of orchids the hay i spread in meadows with no orchids. The sheep eat the hay seeds pass through the sheep speeding up germination. we also spread clover and ox eye daisy passed through an animal really does speed things up. It is the same with horse logging in woodlands the hooves slightly turn the topsoil bringing seeds to the top where they germinate tractors compact and nothing will grow.