Anatomy of an Air Layer

[0soyoung]

I have tangentially sectioned a couple of failed air layers to reveal the internal structure; one of a layer done by girdling the tree (first pair of photos); the other with by a wire tourniquet (second pair of photos). Even though both happen to be black pine layers, the anatomy of layers of other conifers and of deciduous trees is similar.
The swelling that occurs above the girdle/tourniquet is the result of enhanced wood growth. This growth occurs in response to the accumulation of photosynthate (sugars) and auxin above the girdle/tourniquet before roots form.

BTW, recall that the cambium, that thin layer of green under the bark, is what grows. Cells on the inside of the cambium differentiate into xylem and xylem parenchyma (living cells distributed through the wood). Those on the outside differentiate into phloem and eventually into bark and bark parenchyma (living cells in the inner bark layer). Roots grow from cambial cells as a consequence of hormone therapy: auxin - be it externally applied (to a girdle) or otherwise induced by the distruption of the phloem and cambium.

 

[lordy]

Thank you for the in-depth explanation and photos. It goes a long way to educate people like me who do not have the scientific background to still fully grasp all this. It seems clear that you know what you are doing when figuring out what goes on in an air layer.
One question I have is, do you have any clues as to why these two examples did not succeed? I have two trees now that are in the process and am anxious to see what lies inside the wrappers.

 

[Poink88]

Thank you for the in-depth explanation and photos. It goes a long way to educate people like me who do not have the scientific background to still fully grasp all this. It seems clear that you know what you are doing when figuring out what goes on in an air layer.
One question I have is, do you have any clues as to why these two examples did not succeed? I have two trees now that are in the process and am anxious to see what lies inside the wrappers.

My guess is because these are pines.

 

[Jason_mazzy]

pines can and do regularly root.

 

[Poink88]

pines can and do regularly root.

I know but citing that as the probable cause because while they can/will...it usually takes longer and somethings can go wrong between that time (i.e. drying, freezing, pest infestation, mold attack, impatience & poking, etc.)

 

[barrosinc]

I would love to see the same on a air layer that did work, maybe on a sacrifice branch just for science? That would be awesome!

thanks for posting these.

 

[Poink88]

I would love to see the same on a air layer that did work, maybe on a sacrifice branch just for science? That would be awesome!

thanks for posting these.

Tons of pictures online if you search Google for images.

Like these...
https://www.google.com/search?q=air...WC8AH96YCgBA&ved=0CAoQ_AUoAw&biw=1280&bih=860

 

[barrosinc]

couldn't find any besides ilustrations of a tangentially sectioned air layer...

 

[0soyoung]

One question I have is, do you have any clues as to why these two examples did not succeed?

I do.

The girdle layer died because it was on a prior season candle of the tourniquet layer that died. This is the 4 inch pot in the attached photo. All that foliage in the photo is the harvested tourniquet layer. The tourniquet layer died because of desiccation = too much foliage for the volume of roots.

I should have kept the layer on the tree another season and/or removed a lot of the foliage that you see in the photo to have had a better ratio of 'roots to shoots'.

 

[bonsairxmd]

Very cool. Thanks for sharing!

 

[ConorDash]

Wow this is amazingly cool!

Really informative, thank you .

Excuse me if I'm wrong, but I thought after the tourniquet had done its job, you'd still girdle underneath it, in order for the branch to push out roots.
How does it push out roots, without girdling at all? In my head, it'd have to push roots out throug cambium and bark..?
Unless I've gotten really confused.
Really impressed with the amount of swelling that it produced.
Any idea of time periods that these took, too?

 

[ColinFraser]

Wow this is amazingly cool!

Really informative, thank you .

Excuse me if I'm wrong, but I thought after the tourniquet had done its job, you'd still girdle underneath it, in order for the branch to push out roots.
How does it push out roots, without girdling at all? In my head, it'd have to push roots out throug cambium and bark..?
Unless I've gotten really confused.
Really impressed with the amount of swelling that it produced.
Any idea of time periods that these took, too?

Lots of plants will push roots right from the bark above a girdling wire, no cut required. Some will root just by simply burying a part of the trunk - no other intervention required. Cutting the cambium just forces the issue . . .

 

[ColinFraser]

Cool post. How did you section these . . . I'm envisioning a belt sander.

 

[bonhe]

I have tangentially sectioned a couple of failed air layers to reveal the internal structure; one of a layer done by girdling the tree (first pair of photos); the other with by a wire tourniquet (second pair of photos). Even though both happen to be black pine layers, the anatomy of layers of other conifers and of deciduous trees is similar.
The swelling that occurs above the girdle/tourniquet is the result of enhanced wood growth. This growth occurs in response to the accumulation of photosynthate (sugars) and auxin above the girdle/tourniquet before roots form.

BTW, recall that the cambium, that thin layer of green under the bark, is what grows. Cells on the inside of the cambium differentiate into xylem and xylem parenchyma (living cells distributed through the wood). Those on the outside differentiate into phloem and eventually into bark and bark parenchyma (living cells in the inner bark layer). Roots grow from cambial cells as a consequence of hormone therapy: auxin - be it externally applied (to a girdle) or otherwise induced by the distruption of the phloem and cambium.

Let me phrase this:
Girdling/tourniquet -------> obstruction of the phloem system but not xylem ------> fluid collection above the site ------> the branch or trunk is swollen up by obstruction (it is exactly as same as small or large bowel obstruction pathophysiology in human). I have been using this theory to increase the trunk size of young seedlings (if you pay attention to my Japanese black pine seedling post, you can see lot of wiring marks on the lower trunks). The sugar and auxin concentration will be increased in the area right above the site -----> stimulate the root formation from the cambium.
Bonhe

 

[ConorDash]

Lots of plants will push roots right from the bark above a girdling wire, no cut required. Some will root just by simply burying a part of the trunk - no other intervention required. Cutting the cambium just forces the issue . . .

Ah good info, thank you.
Been a while since I've spoken to you Mr Fraser. .

 

[0soyoung]

Cool post. How did you section these . . . I'm envisioning a belt sander.

I used a carving tool on a Dremmel to get most of the way there, then a rasp and finally sandpaper. A belt sander would work nicely, I think (I just don't have one).

 

[0soyoung]

Let me phrase this:
Girdling/tourniquet -------> obstruction of the phloem system but not xylem ------> fluid collection above the site ------> the branch or trunk is swollen up by obstruction (it is exactly as same as small or large bowel obstruction pathophysiology in human). I have been using this theory to increase the trunk size of young seedlings (if you pay attention to my Japanese black pine seedling post, you can see lot of wiring marks on the lower trunks). The sugar and auxin concentration will be increased in the area right above the site -----> stimulate the root formation from the cambium.
Bonhe

Pretty much (if one doesn't get too literal in drawing the equivalence).

While I could easily be fooled, it appears to me that the harder a species is to root the greater the swelling from a tourniquet. Toyonishiki quince, for example, will root by simply keeping the stem damp and does not 'swell' much. Pines 'swell' a lot and are difficult to root (or take a long time).

 

[bonhe]

While I could easily be fooled, it appears to me that the harder a species is to root the greater the swelling from a tourniquet. Toyonishiki quince, for example, will root by simply keeping the stem damp and does not 'swell' much. Pines 'swell' a lot and are difficult to root (or take a long time).

It happens in the cutting, too. It produces big callous right in the cutting area. That is why my teacher always takes a ume cutting out after one month then removes a callous, then put it back to the soil.
Bonhe

 

[vicn]

Wow this is amazingly cool!

Really informative, thank you .

Excuse me if I'm wrong, but I thought after the tourniquet had done its job, you'd still girdle underneath it, in order for the branch to push out roots.
How does it push out roots, without girdling at all? In my head, it'd have to push roots out throug cambium and bark..?
Unless I've gotten really confused.
Really impressed with the amount of swelling that it produced.
Any idea of time periods that these took, too?

Yes, the complete girdling must still be done, the wire (I thought) was to create a greater flare PRIOR to girdling the tree.

 

[vicn]

The consensus seems to be that a wire is pretty much unnecessary for flare. Thanks to all who answered. I'm familiar with layering, just thought if I could speed up a basal flare, I would try this.