I always just thought that dwarfing rootstocks simply had less ability to uptake nutrients and therefore couldn't provide the delivery system to support larger growth. Now that you mention it, I'm sure there is more to it than that.

I am sure the info is out there in this forum.
Just my idle brain making trouble.

Mike

Mike:

I've never heard an explanation. But would think that a number of factors are involved namely hormonal, water uptake, and possibly nutrient uptake. Pots dwarf trees very reliably. I'd think that's mostly limited water uptake. There could also be some affect of the graft union reducing transfer of above factors.

My stone fruit on Krymsk 1 looked very much like the genetic dwarfs, ie very short internodes. Apples on M9 don't appear to have shortened internodes. They just settle down sooner and grow apples instead of wood. That's the big difference in apples, photosynthates are partitioned to fruit not wood.

The question may actually be, why are some humans bigger than other humans. Why are some seedling maple trees more vigorous than others. Why are some seedling apple trees more vigorous than others.

When the English began standardizing dwarf apple rootsocks they started with the actual trees- the rootstocks were selected and categorized in relation to the vigor of the original clone of each rootstock.

A good dwarfing rootstock is that way because of their genes of growth and speed to maturity and not the result of viral infection, as I understand it.

As to the specific manner genes regulate these functions, that is something that's way beyond my pay scale.

But how do the rootstocks choke back the growth of the scionwood which did not have these qualities bred into them.

It is probably best that we not ask why rootstocks behave the way they do. There are people that can answer this question for us, but they are not our friends. We should accept the apple rootstocks and traits that we have at our disposal, and just be thankful we can have something workable.

Every food plant is a potential target for genetic modifications and the associated unknowns for millions of people to ingest. Biotech interests are working with governments to ban seed saving and plant propagation. These actions take away the heritage and inheritance of people worldwide.

The answer to the grower's problems with the apple should come in the form of better and more targeted and safer crop protection materials and in the continued use and rotation of currently used materials.

Here is an interesting article about the apple genome.

Here is a link that might be useful: the immense apple genome

What I find interesting is the effect that is created by interstem grafting. This makes it seem like it isn't the effect of water uptake by the roots or any of the specific activities of the actual roots that are the key part of the equation, since that little piece of interstem material seems to be the major controller of size.

Does it have more to do with the way sap, water or whatever is allowed to flow through the interstem or is there something equivalent to hornmones or other substances added by the interstem that control the size?

Or is there some other type of signaling coming from the interstem that comes from the effect of it being the part that is directly connected to the scion - sort of like those "do plants have feelings" segments on Discovery, etc. Maybe the interstem effects the scions self esteem so it just doesn't feel like growing very tall!

It is mostly written or talked about root stocks influencing the scions and growth of a tree.I was recently reading a book about propagation that brought up the statement that scions can effect,(or is it affect,I'll have to study that)the root stock's behavior.I think mostly it mentioned that a vigorous scion can make a root stock more so. Brady

I bet the specific info is out there and someone like Jim Cummins (who is "one of us", IMO) could break down the answers to these questions piece by piece.

For fun, I could guess that dwarfing interstems simply don't have as active cell generation as vigorous ones and their cambium functions almost like a kink in a hose. It is probably all about the vigor of the cambium itself and its constraining affect on the flow of nitrogen and/or water restricts vigor of the tree above the interstem. It's a hypothesis that's probably already been tested.

The "kink in the hose" concept is a plausible explanation as to the reduced size of the tree... but

What about fact that dwarfing roots stocks make for EARLIER fruit bearing.

Could it be that the "scion" wood is "feeling" threatened and "says... I gotta start producing some seeds before I am taken out".

Mike

It was my understanding that all cells within an organism are synchronized by an internal clock that begins at the time of conception. The genetic map directs a cell's environmental responses based on the time of the clock. The result is specialized cells.

The cells in scionwood are working with an advanced internal clock.

Excellent question!!!! What are the mechanisms of action? There sure don't seem to be much literature on the subject even behind paywalls (Beryl Beakbank has done speculating a a review but even they are scant on actual data).

Dwarfing rootstocks typically dwarf the roots as well. I too always assumed it was less nutrient/water availability and maybe less branch/leaf inducing hormone traveling from root to shoot that dwarfed the canopy as well.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2735327/pdf/mcm114.pdf

http://www.agrojournal.org/17/05-09-11.pdf

When a tree has reduced vegetative growth more of the carbohydrates go to producing fruit. Any rootstock is much more precocious if it is restricted in a pot. Also, I've seen trees where a wire was left girdling one scaffold of a young tree and that scaffold would fruit far ahead of the others.

When you score a tree to shift it's emphasis from vegetative growth to fruiting the same thing is happening. The roots are being starved and the energy goes to fruiting parts.

Exactly...the tree is evolutionarily programmed to produce fruit when it feels it's "livelihood" is threatened. That can be from the result of too little water, light, nutrients, or physical damage. It wants to live on, so it's natural instinct is to procreate to assure the passing of it's genes.

Have any of you ever heard of "beating" your fruit trees into production? I believe it was Thomas Jefferson who wrote of it. They beat the trunks of their trees with chains to stimulate fruiting. It may have instead been Geo. Washington... I don't remember, but when I heard it I didn't believe it. I looked it up...it's true.

RE: BEATING THE TREE TRUNK

I've done some googling on the subject and although I found no HARD research I have found many references that indicate that hitting the trunk of the tree (with anything from baseball bats to chains) just hard enough to sort of "bruise" the trunk works.

The prevalent theory is that the damage to the tree triggers some survival instinct to quickly produce seed/fruit much like deadheading some flowers will produce more flowers.

Below is an excerpt from a page on the STARK BROTHERS site which pretty much parallels what H'man, FN, FN and others have said here but uses root pruning (like growing in pots?) and scoring/notching to stress the tree by inflicting some slight damage. Also below is the link to the entire STARK BROs page.

STARK STARTS HERE: ---> ------ Desperate Times Call for Desperate Measures

There are some extreme solutions that should only be attempted if all else fails: root-pruning or scoring your trees.

Root pruning: Bring a spade or shovel out to the drip line of your trees. The drip line is where the tips of the branches are, but straight down on the ground. Take the spade or shovel and push it straight into the ground and pull it straight back out. Do not dig out any dirt. Move over a foot or two and repeat the process. You are essentially creating a dotted-line circle around your treeâÂÂs root system, which will clip the feeder roots and âÂÂshockâ the tree into blooming during the next growing season.

Scoring: This has the same result as root pruning, but scoring should not be your first step to getting your tree to fruit. Consider it a last resort. When scoring your trees, bring a small knife (like a pocket-knife) out to your tree. Locate a spot low on the trunk and cut a single horizontal line into the bark, only halfway around the tree. Move up several inches and repeat this, but halfway around the other direction. Do not let these lines connect to one another or you will destroy the phloem tissue and completely disrupt the vascular system of the tree, which will lead to its demise. See the animated image as a reference for examples of properly scoring the bark halfway around a tree.

[video - Demonstration of Tree-Scoring]

Mike

Here is a link that might be useful: DEALING WITH FRUIT BEARING PROBLEMS

This post was edited by mes111 on Sun, Nov 9, 14 at 12:50

I don't think it is about stressing in general but about limiting water and N. from below and keeping more carbohydrate above. Beating the trunk is probably just another way of injuring the cambium and reducing transport both ways. The reaction needn't be the result of a survival mechanism although it's fun to theorize and a logical analysis. Some forms of stress reduce fruit production.

As long as the fruits come knowing why is not as important as knowing that it is.

Mike

>> Some forms of stress reduce fruit production.It can be the other way around....
stress can induce fruit production, ..a signal to the tree for growing fruits/seeds for the survival of the species.

A dwarfing rootstock is simply genetically predisposed to be a smaller variety, and as a result the roots become the limiting factor for the growth of the rest of the tree. Severe root pruning can bring about the same results, using bonsai as an example.

If I may change the discussion from dwarfing rootstocks to nondwarfing rootstocks, especially in stone fruits. I planted a number of peach trees this year, some on Guardian and others on Halford, and the ones on Guardian significantly out grew the ones on Halford.
Is there a scientific reason for this, or as Vince Lombardi used to say, 'What the hell's going on out there."

Yeah...just wanted to point out that I only brought this up to support the injury/stress vs. fruiting concept.
I'm not actually advocating this practice as a good idea. I think it's a terrible idea.
Not sure if there was any confusion or not...just wanted to be clear on that.

Maybe someone who is planning the removal of an unliked tree could spare it another year for scientific experimentation. You know...got to the shed get some logging chain or whatever and then go beat the Hell out of said tree...lol.
Report to the forum of the post thrashing fruit set or death of said tree.

Rayrose, maybe it's just a sign that your soil is infested with nematodes. Isn't that what Guardian is for?

There's an example of stress that doesn't lead to earlier fruiting, I think.

Just answered my own question with this excerpt from the Southeast Peach Growers Guide.

Current peach rootstocks used in the southeastern states are all vigorous, with Nemaguard, Flordaguard, and Guardian being more vigorous than Lovell or Halford.
Sorry, Vince, now I know what's going on out there.