Air layer branch more leaves

[spunog]

Hi,

I have done an air layer this spring on a maple. I’ve noticed that the are of the tree above the layer has significantly more leaf out than the other areas . I hope it is noticeable in the photo attached.

Theory 1
There is more moisture coming from the air layer area which is supplying water to the branch. I don’t know how feasible this is as I thought moisture comes up from the roots and there would not be roots in he layer yet .

Theory 2
The tree has identified an injury and has pushed leaves in that area in order to get the sugars moving down to heal the wound .

I would be interested to hear your opinions on why this is occurring.

It is not a problem as such but I find it interesting.

Regards

Spunog

 

[Wires_Guy_wires]

What about the sapflow being interrupted and not flowing back into the tree?
Meaning this branch is supporting itself and it's being supported by the rest of the tree. The branch itself is not supporting the rest of the tree, so it has all the energy for itself.

That, and rooting hormones and damage response, would fit the puzzle perfectly.

 

[0soyoung]

I don't think one observation supports or refutes any hypothesis. Nor would simple models of how trees work, IMHO.

A basic is that an excess of cytokinins relative to auxins releases buds --> in practice, a deficit of auxins relative to cytokinins (i.e., pruning effect). Cytokinins are synthesized in the roots and are conducted up the tree in the xylem, driven by transpiration. Girdling would not change this as the xylem is still intact. In fact it could be reduced because of xylem scraped/cut away at the girdle and damage response in the girdled region. Auxins are made by buds and leaves some of which are with carbohydrates from photosynthesis in the phloem (inner bark). These are accumulated/used/consumed only above the girdle. Further, biologically active auxins are carried like a bucket brigade from one cambium cell to the next strictly downward toward the roots. This leads to the production of ethylene and ethylene precursors just above the girdle and drives the process of generating adventitious roots. Local ethylene production causes the swelling one inevitably finds just above the top of the girdle. Precursors that get dumped into the xylem flow will cause leaves of the layer to color to some degree like they do in fall, but there is nothing in this 'easy stuff' that would lead to more leaves on the layer.

My conclusion is that you're being fooled by a mere coincidence. But to make/break your case one would need to count leaves on two branches in one season, then again the next after girdling one of them. Then one also needs to do this on multiple trees; at least 5 observation sets would be needed to have a fair estimate of the average difference in leaf counts.

There is a phenomenon called 'correlative inhibition' wherein what happens to one branch influences others, that could explain what you think to be happening. Strigolactones are believed to be responsible for this and also to be the real cause of bud inhibition. This is a current research topic and isn't 'easy stuff'. Welcome to the weedscutting edge, @spunog.