Stem tissue, root tissue and rooting hormone

Jay Wilson

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I've had this question running through my mind for a couple of years now.
Actually it's a multi part question mainly about decidious trees.

First part: I have read many places that rooting hormone is used for converting stem tissue into root tissue and that using rooting hormone on root tissue is/can be harmful to the root cells thus being counter-productive if you are trying to make roots grow more roots. Truth or myth?( If this is true, why do people talk about putting hormone on cut roots before potting?)

Second part: I assume that the dividing line between root tissue and stem tissue ( in a undisturbed, grown from seed tree) would be at or around ground level. Here's where it gets tricky...If you pot a tree higher in the pot and expose some of the trunk that was under ground (and presumably root tissue) does the tissue change to stem tissue or does it keep its root cells and just bark up?

Now here is the crux of the question I have:
If I had a tree that had been raised up a few inches from the natural soil line for a few years and I wanted to do a ground layer on this just at or above the new ground level, shoud I use hormone....or not?

I'm not at all sure that any of this makes sense so if it doesn't, sorry in advance.

Jay
 

Graydon

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Good questions Jay. This is a discussion that I will be interested in seeing more of here. Do some research on the term "root crown" and I believe you will have some of your answers.
 

Tachigi

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Hi Jay, In a thread I started a few weeks ago Fun with rooting hormones. I basically tried what your question asks in an impromptu experiment. I have a several large acers that have less than desirable nebari. There is basically a 4 inch gap between each root protrusion. So what I did was to band an area between the roots and apply hormone in my case 3%. I know over kill with acers but there was a reason I did it that I will get into later. With in two weeks time I had sucker growth coming from each spot that had been banded. This in itself was interesting. Did the hormone stimulate advantageous buds and was there anything going on below the soil line? Today being overcast and rainy I ventured out and peeled back just a small bit of the soil to see what was going on. There below the sucker growth was some fine hair roots, at least on this one tree and in this one particular spot. So I would venture that rooting hormone applied to the base of the trunk will produce roots and not on roots themselves.
 

bretts

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I like your questions Jay:)
Rooting hormones have the active ingredient Auxin. Many people will say that rooting hormone on roots will kill and burn and should only be used on stem tissue to stimulate root growth. This is partly true. A weak/small amount of the hormone Auxin on roots increases lateral root growth. Higher concentrations like those found in "Rooting Hormone" will burn the roots.
I have heard of people sprinkling "rooting hormone" in with the roots when repotting or making a mix with water and dipping the roots when repotting. I guess they are aiming for a low dose of auxin. Unless I had a "master" explain the exact amount and strength of ingredients to do this I would not attempt( maybe not even then) as getting the mix rong could very easily kill a tree.
Auxin is used in this manner as a lawn weed killer. Broad leaf weeds pick up more of the auxin than your lawn hence "weed and feed" helps the lawn kills the weeds.
There are safe ways to utilize auxin in repotting though. Super thrive has it as a main ingredient but that is expensive. I found a product called plant starter with auxin as the active ingredient.
I have recently found that sea weed extract is another great sorce of auxins that also has many other great elements for trees. It has been said that Auxins work best for trees in stress.

As to how stong doses of Auxin "rooting Hormone" increase root development on stem tissue I have also wonderd. I think the explination is in here http://en.wikipedia.org/wiki/Auxin some were. It may be as simple as the older wood can handle stronger doses of auxin and it may have little to do with were on the tree it is.
There are a few other known hormones that interact with auxins to rergulate plant growth and it may be something to do with the levels of these that will define what is root and what is stem.
I am keen to understand all these hormones and thier possible uses in bonsai growing.
 

Jay Wilson

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Graydon,
I hope there is some good discussion on this subject. I certianly need to learn more.

Tom,
I remember that thread... It's the thing that got me motivated to start this thread.
A couple of questions about your experiment ( though maybe I should ask in that thread instead of this one)
Is the sucker and root growth above the banded area?

Bretts,
Great reply with lots of information.
Thanks for the link, it's given me lots to follow up on and think about.



I haven't got time right now but later I'll post a couple of pics showing what got me thinking about this.

Jay
 

Tachigi

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Jay
Is the sucker and root growth above the banded area?
Yes it is. It was encouraging as that is where its suppose to be. The sucker growth was unwanted but can be fixed easily enough.
 

Brent

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I like your questions Jay:)
Rooting hormones have the active ingredient Auxin.

Bretts
Yes, but there are several compounds in nature that function as auxins. The two most common are IAA, NAA and IBA. IBA is the one used mostly in rooting compounds. Some of the liquids also contain NAA. Other compounds can act as auxins which I will touch on below.

Many people will say that rooting hormone on roots will kill and burn and should only be used on stem tissue to stimulate root growth. This is partly true. A weak/small amount of the hormone Auxin on roots increases lateral root growth. Higher concentrations like those found in "Rooting Hormone" will burn the roots.

Do you have a source for this statement? (A weak/small amount of the hormone Auxin on roots increases lateral root growth). As far as I know studies have shown either no effect or a mild rooting inhibition, even in small quantities. I can't give you an exact study, but this can be found in the most comprehensive compendiium on the subject: Aventitious Root Formation in Cuttings, Davis, et al.1988.

I have heard of people sprinkling "rooting hormone" in with the roots when repotting or making a mix with water and dipping the roots when repotting. I guess they are aiming for a low dose of auxin. Unless I had a "master" explain the exact amount and strength of ingredients to do this I would not attempt( maybe not even then) as getting the mix rong could very easily kill a tree.

Correct, this can happen, but usually only with very concentrated mixtures. I wouldn't do it at all since efficacy has not been proven.

Auxin is used in this manner as a lawn weed killer. Broad leaf weeds pick up more of the auxin than your lawn hence "weed and feed" helps the lawn kills the weeds.

Here is where you are confusing auxin used in commercial mixes (NAA, IBA) with what was formerly used by some intrepid souls in the past. 2,4-D has auxin effects when used in very small quantities. I don't think any of us want to be messing with that stuff, even if we could still get it.

There are safe ways to utilize auxin in repotting though. Super thrive has it as a main ingredient but that is expensive. I found a product called plant starter with auxin as the active ingredient.

This is promoted endlessly without any substantial work to back up the claim. We don't even know for sure what is in ST since the manufacturer won't reveal the contents. One thing it does make is lots of money. Many people who have sworn by this stuff have discovered, after running out of it and just using sound hort practices, that hey! my plants are doing just as well as they used to. Others rationalize that it can't hurt even if there is only a small chance that it works. I don't think this is true. It is easy to come to rely on such elixirs and neglect the sound, proven ways of promoting plant growth, even in small ways that can make a huge difference. For example, you have plant that is showing chlorotic symptoms, it is very easy to immediately think that ST might do the trick and spend a month or two waiting for it to work rather than really investigating the cause of the problem.

I have recently found that sea weed extract is another great sorce of auxins that also has many other great elements for trees. It has been said that Auxins work best for trees in stress.

Said yes, shown, no. Seaweed does have some important minors and trace elements, so if your plants are deficient in these (and it is rare that this happens), than it could help. There is also the mild fertilizing function that can be accomplished in other ways.

As to how stong doses of Auxin "rooting Hormone" increase root development on stem tissue I have also wonderd. I think the explination is in here http://en.wikipedia.org/wiki/Auxin some were. It may be as simple as the older wood can handle stronger doses of auxin and it may have little to do with were on the tree it is.

The strength of auxin that works best on stem tissue to promote roots is an enormous area of study. Thousands of IPPS (Internation Plant Propagators Society) reports are published. I think the best of these reports can be found in The Reference Manual of Woody Plant Propagation, Dirr and Heuser, ISBN 0-942375-00-9. Anyone who does more than a few cuttings should have this book. The strengths used depend on the species (often even the cultivar), the physiological state of the wood (hard, soft, semi hard, etc), time of year, method of application (solid, solution), acid or salt form of auxin, time of auxin contact, etc. Concentrations of auxin that are too high can even inhibit rooting, and in the extreme cause stem tissue necrosis.

There are a few other known hormones that interact with auxins to rergulate plant growth and it may be something to do with the levels of these that will define what is root and what is stem.
I am keen to understand all these hormones and thier possible uses in bonsai growing.

It is important to understand the difference between endogenous and exogonous auxin effects. Endogenous effect is the plant's own system of moving auxin from the leaves and buds to the roots through the vascular system. This causes root growth at the tips where the auxin is destroyed. Knowledge of this is what has caused the great debate. The presumption is that exogenously applied auxin (from outside the plant tissue) should do the same thing. But studies have consistently shown that it doesn't happen. There is no effect. Think of it as spreading gasoline over your car instead of putting it in the gas tank where it can work its way to the engine.

Brent
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see our blog at http://BonsaiNurseryman.typepad.com
The long blog hiatus is nearly over!
 

Tachigi

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Bret, thanks that was very informative. How do you manage to cram all that data in your skull. :)
 

bretts

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Here is an article from a Professor that I believe is also a bonsaist but I have not looked this deep into it for a while.
http://www.puyallup.wsu.edu/~Linda Chalker-Scott/Horticultural Myths_files/Myths/Vitamin B1.pdf

Here is the lable for 1 gallon of Super Thrive. I have only been doing bonsai for a bit so I was suprised to find the ingredients listed on this lable and not a great secret like I had been told??? (I thought that would be illegal at least in Australia)
B1 and an Auxin called Naphthyl acetic acid are listed as active ingredients.
http://www.superthrive.com/gallon.html

I am in the middle of a project today so I must go but I will look into finding some of the more technical info I have found in the past about this.
I look forward to getting to the bottom of this.
 

Tachigi

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What I think the US contingent isn't aware of is that in Europe and obviously Australia. That truth in advertising is truth in advertising and that it is serious offense to make claims that aren't true and they must disclose ingredients. Something the Fed and corporate America has yet to adopt.

Still think the claims are a bit outrageous whether your here or overseas ;)
 

bretts

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I spent some time looking for the info that I had seen on the internet about this but had lost over the years. Phew! I seem to be getting closer to an understanding of this issue.
This from Thimann, K. V. , Biol Rev. Camb. Phil. puts it in a nut shell.
http://www.nature.com/nature/journal/v170/n4322/abs/170372a0.html
More on this can be read here
http://links.jstor.org/sici?sici=00....0.CO;2-1&size=LARGE&origin=JSTOR-enlargePage
and here
http://www.pnas.org/cgi/reprint/64/2/495.pdf

What this gets at is that If auxins are lacking for any reason then getting them back to optimum levels is benificial to root growth.

I can think of many ways that auxin can be lacking in bonsai culture.
But first some may need to read this.
http://cmg.colostate.edu/gardennotes/145.pdf
The obvious two would be when collecting due to top/tip prunning or if this was not done tip die back.
The other would be when prunning is done. As this is often done at the time of root prunning the reduction in auxin from this would retard root regrowth at the time it is needed the most.
Less obvious would be when the tree is under some type of stress say from heat that has burnt the tips and possibly roots in the bonsai pot as well. Again we have a time when auxin may be lacking and quick root growth is of benifit.

So as stated by Super Thrive and the Auxin based "Plant Starter" I mentioned and Seaweed extract that all contain some type of Auxin, It seems there is evidence that they can help againts transplant shock and stressed plants/Trees.
 

bretts

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Brent it seems that 2,4-Dichlorophenoxyacetic acid is still in common use as a weed killer. From looking into it it seems that it was mixed with agent orange in vietnam as a weed killing concoction. Although it is not stated as being that toxic and still available to the public in most contries including america "In 2005, the United States Environmental Protection Agency approved the continued use of 2,4-D:

apparently there are less toxic ones available now.
I had just been pretty well clasifying all auxins the same but it does seem they have different attributes and tests can be alterd by use of different Auxins.
http://en.wikipedia.org/wiki/2,4-D
I know it's only Wki but the rest of the internet seems to agree.

The strength of auxin that works best on stem tissue to promote roots is an enormous area of study. Thousands of IPPS (Internation Plant Propagators Society) reports are published. I think the best of these reports can be found in The Reference Manual of Woody Plant Propagation, Dirr and Heuser, ISBN 0-942375-00-9. Anyone who does more than a few cuttings should have this book. The strengths used depend on the species (often even the cultivar), the physiological state of the wood (hard, soft, semi hard, etc), time of year, method of application (solid, solution), acid or salt form of auxin, time of auxin contact, etc. Concentrations of auxin that are too high can even inhibit rooting, and in the extreme cause stem tissue necrosis.
But does it explain when stem becomes root and the "rooting hormone" can't be used. I guess that rooting hormone is used when doing root cuttings.
So I guess it can't be said that Auxin should not be used on roots but only that varying degrees of strenght should be used for all situations where Auxin is deficient.

It is important to understand the difference between endogenous and exogonous auxin effects. Endogenous effect is the plant's own system of moving auxin from the leaves and buds to the roots through the vascular system. This causes root growth at the tips where the auxin is destroyed. Knowledge of this is what has caused the great debate. The presumption is that exogenously applied auxin (from outside the plant tissue) should do the same thing. But studies have consistently shown that it doesn't happen. There is no effect. Think of it as spreading gasoline over your car instead of putting it in the gas tank where it can work its way to the engine.
This seems to ring true to what I understand except that "exogenously applied auxin (from outside the plant tissue)" You say it is not able to be absorbed by the tree. Although I have found much confusing and some times seemingly contradictory information, I have never seen any mention of exogenously applied auxin not being able to be absorbed.
I would ask you to show the source of consistant studies showing this as you state.
Thanks for your time in this and I look forward to your further input:)
 

bretts

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Sorry I missed an issue :)
Many people who have sworn by this stuff have discovered, after running out of it and just using sound hort practices, that hey! my plants are doing just as well as they used to. Others rationalize that it can't hurt even if there is only a small chance that it works. I don't think this is true. It is easy to come to rely on such elixirs and neglect the sound, proven ways of promoting plant growth, even in small ways that can make a huge difference. For example, you have plant that is showing chlorotic symptoms, it is very easy to immediately think that ST might do the trick and spend a month or two waiting for it to work rather than really investigating the cause of the problem.
This is why I wish to understand this issue so that the auxins are used in a sensible manner for the ailments that they can help with. Sound hort practices will prevent many pests and diseases but we are still skilled in the use of fungicides and pesticides;)
 

Brent

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Well, my internet service is down the morning, so I am just going to type this and then copy and paste it to Bnut. I think I can remember most of the salient points of Brett's last post. I keep thinking I am going to get a chance to check my files and books to find the citations asked for and that would back up my arguments, but it just isn't going to happen. I am in the middle of propagating which must be finished in two to three weeks. Besides, I have been all over this ground many times before and if anyone wants to look it up, they can go to the IBC archives or search the other forums for the relevant posts. It will be more readable this way anyhow.

Root Tip Absorption of Auxin
I never said that root tips could not absorb IBA or other auxins, clearly they can. What I said was that the studies to which I referred showed that there was no effect of adding auxin exogenously similar to that of auxin transport endogenously. At first glance this must seem a bit bizarre. If the leaves and buds make and transport auxin compounds to the root tips then send cytokinins back to the meristems (shoots and buds) where it acts as a growth stimulant, then why shouldn't adding auxin do the same thing?. I don't think anyone knows the answer to this. It just means that the process is more complicated then simply adding an auxin compound. Understanding the cycle however is important. The cytokinins produce an increase in foliage and buds creating more auxin for transport back to the roots. This is the reinforcing cycle that makes plant growth, top and bottom. It occurs along somewhat defined pathways, so that the particular leaves and roots connected directly get preferential treatment. Leaves and buds that are shaded out thus producing little auxin send a weak signal to the roots, and if there is an actual carbohydrate/auxin deficit at the leaf, then the affected roots will actually wall this area off. That's how trees lose their lower branches. This simple model is VERY important to understanding plant growth and (for us) pruning practices.

Now if roots could absorb and USE auxin exogenously in the same way that they use it endogenously, then we could do all sorts of things like the root stimulant/elixer makers promise. But this isn't the case. The study I mentioned showed no effect to a slight inhibition of root tip growth. I am prepared to admit that under some circumstances there MAY be some mild effect. My point is that even if it does happen, it is not significant, particularly in the system under which we grow plants (which I discuss in the next part). IF this were a significant effect, we would see it and accept it, and not endlessly argue about it. In any case, the most powerful tools for root growth already exist in the plant. With judicious pruning, taking care that the timing is correct, and that some auxin forming leaves and buds remain following root pruning, the plant will heal itself with a better tool than root elixers. But this requires THINKING and UNDERSTANDING plant growth and taking appropriate steps, it's a whole lot easier to add ST and hope for the best, and it is this attitude that I am constantly battling.

I don't really care if you use this stuff, and it certainly won't do any direct harm, but I am irked when people promote this is an effective technique under our system of growing, especially when they don't even mention the much stronger horticultural tools that ARE available if they only took the time to learn them.

The B1 Debate
This seems never to be settled. As far as I know, this came about early in the last century when a study showed some mild effects of B1 on certain plants under certain specific conditions. Endless studies since then have shown no SIGNIFICANT plant growth stimulant effect. But the beast never dies. Do some more searches for citations, I have seen them all before. Jim Lewis writes about this a lot on the IBC, so that might be a place to start looking.

Support of Root Elixers, B1, Foliar Feeding, and other Dubious Techniques
Foliar feeding is another one. Sure you can find studies that support the notion that leaves CAN indeed absorb nutrients through their surface. But what is the natural mechanism of nutrient uptake? The roots of course. Leaves are designed to EXCLUDE the introduction of chemicals, and seal in moisture, thus the heavy, waxy cuticle. The studies cited will usually be of some forest on the outskirts of nitrogen polluted cities where the native soil is almost totally nitrogen deficient. Well, sure, under THOSE conditions gas absorption of nitrogen compounds might make a significant difference, but what has that to do with container and garden conditions where plants are usually overwhelmed with nitrogen sources. Foliar feeding is sometimes used to correct mineral deficiencies where the element is difficult to transport through the vascular system, such as calcium deficiencies. Nitrogen however is very mobile and is transported throughout the plant to wherever it is needed the most. Phosphorus and potassium as not quite as mobile, but the roots have no difficulty in moving them to all parts of the plant.

It's the same thing with the mycorrhizae proponents. Under some extraordinary conditions, plants live in a symbiotic relationship with certain species of fungi. It's a very cool phenomenon, and it has nothing to do with container and garden cultures where these conditions don't exist. MOST myc species cannot even survive in the nutrient rich media in which we grow plants.

Seeking out magic additives is not going to give you healthy plants and good bonsai. Learning about growth principles and applying sound, proven horticultural practices WILL. I have spent the last thirty years reading, studying, and applying these principles in real world systems of garden and container practices. I have tried to debunk many myths and have developed some unique techniques for applying these principles, particularly to bonsai culture. As a nurseryman, you get a unique perspective on plant growth, and you also learn what works and what doesn't, or you are soon out of business.

Using Auxin to Stimulate Adventitious Root Formation in the Root Crown Area
At some point exposed root tissue at, and slightly below the root crown area can become very woody and almost indistinguishable from stem tissue. Even surface roots can take on this appearance. I am not qualified to say whether this exposed tissue actually becomes stem tissue, but in many ways it behaves that way. I can give you my experiences with trying to stimulate new lateral roots in this area.

It seems to be highly species dependent. Species that will layer easily will also layer (often ground layer) in this area such as Acer species, particularly Acer palmatum. This can be done by girdling, removing the bark, or by creating small wounds. At least in Acer species, it doesn't seem necessary to use auxin. Indeed auxin isn't necessary for most stem layers either since the process uses the plants own auxin sources which build up at the wound site unable to travel farther to the roots. I should have an interesting report with photos this winter on this very subject since Bob and did some extensive wounding of very large Japanese maples that I obtained from Oregon Bonsai. The wounds were created with a 3/16 inch punch which made a neat clean round hole quickly and with little effort. We placed these holes all around the proposed nebari wherever we needed more smaller roots. I just checked the maples yesterday and they are now tight in the pots, so we should be able to partly uncover the roots this winter and photograph the results.

In pines this is more difficult and may require more time and the use of auxin. I have done this many times to small plants, scarring the area with razor blades and rubbing in a high IBA (3%) rooting hormone. Unfortunately, I haven't been very good at following up on this. Plants easily get lost when you deal with as much material as I do. But I do recall clearly where this was successful on a grafted Japanese white pine, Pinus parviflora. I was trying to get it off the understock and new roots did grow out from the wounded areas of the P.p. scion. At the time I examined them, they will nice woody roots but not too large and certainly not large enough to support the tree at the time. This would have been several years after the operation. I lost track of the tree after that, but I think it is still somewhere in the nursery.

I should point out that this is a totally different subject than using auxin solution as an elixir to increase the amount of lateral roots and root tips. In these instances we are talking about breaking of root buds on very old wood almost in every way similar to forming adventitious root formation on stem tissue. Indeed, it may be EXACTLY the same thing. Increasing roots from clearly defined root tissue is another subject altogether.

Heavy buried roots are often cut when transplanting and repotting. This results in the formation of new lateral roots at the cut site. This occurs on virtually all woody species (at least in my experience) without the use of auxin. Again this is similar to a layering process, except the lower part of the root is removed. I think we all have witnessed this although you may not have thought about it in these terms.

So is there a use for root elixirs here? If there is, I don't see it, but again it won't hurt if it makes you feel better.

............

I am sure that I am forgetting a few things and I will try to get back to answers questions and review Bretts last post again, but now I have to post this and go water.

I don't mean to cast aspersions on Bretts with this post and I thank him for stimulating me to take the time to write this. I always enjoy a good debate. I just wish I had more time to do it properly...someday!

Brent
EvergreenGardenworks.com
see our blog at http://BonsaiNurseryman.typepad.com
 

bretts

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Thanks for taking the time Brent.
I will look forward to further discussion. I don't think this answers the issue yet.
I am aware of the discussion on this issue at the IBC. I had a couple of these discussions with the ultimate "Stuper Thrive" hater Jim Lewis. But you can see from this thread there that I even had him conceed that he will keep the book open on Auxins.
http://internetbonsaiclub.org/index.php?option=com_smf&Itemid=132&topic=17988.0

He and others refuse to see that Linda Chalker-Scott Phd has gatherd from reviewing current and historical literature That IBA has had some success in root generation in transplanted trees and NAA enhances lateral root growth. This may account for NAA success in regenerating roots in transplanted trees. They both supress crown wich may also redirect resources to the roots. All this stated by Linda

It does seem we can do without Auxins but why should this be about wether we can do without it when there can be many uses for it. Especialy for hard to collect/transplant trees.

The information I gave in links shows that external Auxin can be used by the plant to great effect when Auxins are low. I look forward to when you have more time to go over this information and get back Brent.
I throughly enjoy your aticles Brent(I have almost everyone printed out) and your blog. I don't think there has been much new stuff latley.
In fact I got introuble at the IBC from jim for stating That yours is the most reliable information on the internet, as he took this as a put down of the IBC's info. This and other infractions by Jim are the Reason I don't make full use of the IBC anymore.
The project I am on is a pergola to give my trees dappled shade in the Australian sun so I better get back to it otherwise it won't be ready by spring.:cool:
Oh and good luck with the cuttings even though I doubt you need it.
 
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Brent

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I will try to take these issues one at a time. First let me comment on collected material. The disclaimer: This is not my domain. I only got my first collected tree a year ago, a Rocky Mountain Juniper from Oregon Bonsai, and I am baby sitting some of Bob's Ponderosa pines and an Engelmann spruce from the same place. I haven't killed anything yet. I want to make it clear that I am speaking about collected WILD trees as opposed to collected landscape trees, which I have a done a fair bit of.

Although, I don't collect, or handle collected trees, I am somewhat familiar with the issues and may have some insights into the problems. It is a big mistake to think that the same solutions that we use for nursery material is going to necessarily work for collected material. And Bretts may be right about auxin being important in root growth in this one specific instance. I don't buy that lack of auxin is ever an issue in properly grown nursery material, simply because the growth is nearly always vigorous and lush. Even mature show trees can't come anywhere near the deficient state of collected trees.

I had a long talk with Randy at Oregon Bonsai on this very subject. The issues, for those who are not familiar with the problems of collected trees revolve mainly around the lack of vigor. It isn't simply a matter of the amount of roots you can collect, but a deeper problem which I think is a root/crown pathways issue. Collected trees simply don't respond to fertilizer, water, and good soil like nursery trees, even when you can get a fairly decent rootball like Jason and Randy do.

I believe the major problem is the constriction of the vascular system from decades of almost infinitesimally slow growth. Hundred year old trees might only have a once inch caliper. The tiny growth rings reflect the incredibly small size of the vascular tubes. Growth in nursery and most landscape plants is based on a system of almost perfect conditions with big chunky vascular systems that easily pass water, nutrients, and especially hormone compounds back and forth from the roots and the foliage. Even severely compromised trees with very little root systems (think bare root fruit trees) respond fantastically in a single season. I believe this is because the plumbing is still in place even though the root system is minimal. This allows strong auxin signals to immediately reach the roots after bud break. Only water is necessary to open the buds and get the process going. This is a one way street until the roots grow and become somewhat established, Once a critical degree of establishment takes place, a shot of cytokinins is sent to the terminal bud and a shoot is formed, and the tree is off and running. You have probably witnessed this dozens of times and never realized what was happening. All of this can occur because of the healthy vascular system.

It is this system that is absent in collected wild trees (at least the best ones). This cannot be overcome in a single season, and fertilizers, nutrients, light, water, and the usual high level of care that we provide cannot immediately overcome it. It some cases it may even compromise the recovery. I have heard it said more than once that high levels of fertilizers can seriously compromise or even kill SOME species of old collected wild trees. I think the jury is still out on that one, but I will throw it out there as a possibility.

Well, that's something to think about for now, probably more later.

Brent
EvergreenGardenworks.com
see our blog at http://BonsaiNurseryman.typepad.com
 

bretts

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At first reading I was very happy with your response Brent. Someone who I respect as much as you stating I may be right to some degree. But the more I read it ther more I saw the lack of actual substance to what you have said.

I think I must take some ground here.
I stated that Super thrive had Auxins in it. You stated we did not know what was in Super Thrive. I believe I showed proof that we did. Yet this has not been acknowledged by you.


You asked for a source for the statement "small amounts of Auxin can increase lateral root growth" and stated that Studies have consistently shown that exogonous auxin has no effect. (I took the comment that it was like pouring peterol over the car instead of in the fuel tank to mean that exogonous auxins could not be absorbed by the tree.
I gave several sources for this statement yet you have not given any coment on them but you now say auxins MAY be of benifit in root growth to a collected tree of continued slow growth.


You say it is not the case that exogonous auxins can be used by the tree but then go on to say a mild effect may be possible. It seems to be a bit of both ways while kicking super thrive in the head.

I can understand why you wage a war against super thrive as the ingredient B1 seems to have taken alot of credit for improved root development that it stole from Auxin, but that should not mean a war against all of it's ingredients.

I have shown sources that state that exogonous auxins have increased root development in the lab and in the field.

I agree with your statements that most often trees produce enough of thier own auxin and there is no need for any to be added.

If you were to say that auxins added to a collected tree of slow growth over many years MAY be important in root growth. Were MAY is meaning some times it does help and for any reason some times it won't. I would say great. But it seems to me you state that I may be right about it being of benifit or I may be wrong wich I guess includes the studies quoted and are now sitting on the fence?

I must say at this piont even though I am excited about the possibilities of auxin I am after the truth to this matter.

I put it to you that exogonous auxins can be used by trees but usually there is enough of its own auxin that it gets drowned out. If there is agreement that auxins can be of benifit to the collected tree example you gave I would say we will find other uses
The collected tree example You gave is not one that I really thought of but makes alot of sense. What is of some debate in Australia at the moment is wether growth stimulators(I don't think any one has pinned it down to Auxin like I have) will be any use to our native trees that are hard to collect and transplant. I have no understanding of why some of our natives are hard to transplant apart from the fact that it is hard to pick the dormant and growing periods. I would believe you if you said you were not experienced in our natives so I am leaving this for now.

I can leave you with another interesting link.
http://www.sciencedaily.com/releases/2007/06/070618134342.htm
I reckon this smells of auxin. Take notice that even though these trees have stunted growth. "Root development also appeared to be very strong, which might provide increased stress tolerance and have value where extensive root development is needed, such as in bioremediation of polluted soils or in very windy, limited soil moisture situations."

"These compounds are also used as sprays to control the size and fruiting of orchard trees"
These compounds sure sound like auxin to me.
 
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Jay Wilson

Shohin
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Brent and bretts,
This has been a great thread so far!
I really appreciate your taking your time to research and share your knowledge.
Ya'll even answered my original as best you could....Thanks!

Much more important than my question being answered is the better understanding I think I have about how trees grow and react to things. I've thought I've had a reasonable understanding of how to help trees direct growth or strength where it's needed but after reading all this, I think I have a much better idea of what is happening as a result of my trimming and pruning.

Thanks,
Jay
 

Brent

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Sorry it has taken me so long to get back to this thread. I have spent something like twenty hours reviewing studies on the net trying to make the link between exogenous application of NAA (a root hormone often used for adventitious rooting in cuttings) and stimulated root growth in transplants. This is what root stimulants are supposed to do. You would think that someone, somewhere, would have published a study to show if these root stimulants using NAA were really efficacious in a real world nursery situation. Finding evidence either for or against any effect is elusive, but I have found several references.

Bretts gave me several links to read, which I have done in addition to the thousand or more that I also found. I have found evidence from a few studies that treatment with NAA can be beneficial to seedling transplants in some situations for some species. Nearly all of the hits you get when you google the words exogenous, NAA, roots, will give you citations identical to, or similar to the ones Bretts cited. These studies for the most part were done in the '30's and were experiments on excised root tips to show that IAA (the natural equivalent of NAA) is the root growing hormone produced by the leaves, buds, and shoots. These studies are all done on non woody plants, often unbranched seedling roots in culture. One could read these and understandably make the leap that treating roots with a hormone solution might do the same thing in growing woody plants. But it is not that simple, as I pointed out with the car/gasoline metaphor.

In my opinion, although there are some effects of NAA treatments on woody plant roots in some situations, it is probably not significant in container culture in which all the environmental factors are tightly controlled. After reading all these studies, I have to stand by that assessment. The main reason that I still believe this is that any effect would be greatly overwhelmed by the other effects that are natural plant responses in an ideal environment. As I pointed out previously, the danger of buying into the root stimulant argument, is that people often will ignore the good, solid horticultural techniques that are proven and time tested in favor of the easy route of just adding a pill. Believing in a stimulant is easy, researching the applicable physiological solutions is more difficult. The strong tools for enhanced root growth are:
1) maintenance of as much foliage, bud, and shoot material as possible (given that transpiration is also a factor in transplants).

2) Root pruning, particularly the removal of primary root tips has a very strong effect on the growth of lateral roots, many times the effect, if any, of exogenously applied NAA, and is applicable to all species and all environmental situations.

3) Simultaneous moderate application of nitrogen fertilizer to the root zone (yes, avoiding nitrogen fertilization is myth).

4) Maintenance of an optimal stress free environment that allows retention of the maximum amount of buds, leaves, and shoots to drive the natural IAA hormone machine.

5)And this was a surprise, avoiding phosphorus in the fertilizer at transplant time. (avoid iron and sulfates as well)​

As for Dr Linda Chalker-Scott's website and work, I applaud her myth busting work and agree with most everything she espouses, although I think she has a tendency to overdo it. She is also quite a controversial expert which you can get a taste of here:

http://forums2.gardenweb.com/forums/load/design/msg0213585812574.html

When you read what she has to say about myths, you must bear in mind that she is talking about landscaping for the most part, for which the only equivalent for us would be field growing. She does suggest that root stimulants MAY (her word) help in transplanting by redirecting resources to the roots instead of top growth, but I have not been able to find any study to confirm this for other than seedlings, and again, she is talking about field growing, not container growing, which a whole different ballgame. Container growing creates an ideal environment, field growing is about overcoming soil limitations.

I have written extensively about the effect of top pruning on root growth in transplant situations. Although I haven't done controlled studies, I have strong anecdotal evidence that indeed, retention of as much foliage and buds (especially terminal buds) has a strong effect on root growth. See this article on my website: http://www.evergreengardenworks.com/rootprsd.htm

A study on the effect that top pruning can have on woody plant seedlings can be found here:
http://www.afs-journal.org/index.php?option=article&access=doi&doi=10.1051/forest:2006067

I have found several studies and references on the effect of NAA on root growth. I have considered them all in making my conclusion about the use of root stimulants. I have listed the pertinent ones below, and you can decide for yourself if you think an NAA transplant solution would be beneficial in your particular circumstance.

Exogenous application of NAA can stimulate lateral roots:

[endogenous] Auxin and cytokinins are key factors in determining lateral root initiation. Exogenous auxin induces a extra lateral roots in a dose dependent manner (ie. more auxin, more lateral roots). Conversely, many auxin mutants show a paucity of lateral roots. Environment also influences lateral root development. Lateral roots in nitrogen deficient environments will respond to applied NO3- by elongating. This requires the function of a myb transcription factor called ANR1. Lateral roots of antisense ANR1 plants do not respond to nitrate. This also demonstrates that this is a specific response to the nitrate stimulus and not simply a nutritional response because the antisense plants are otherwise healthy.
http://www.public.iastate.edu/~bot.512/lectures/Roots.htm

Also see this interesting study:

Transplanting often causes root damage, and rapid root growth following transplanting may help to minimize the effects of transplant shock. The objective of this study was to determine the effects of NAA and IAA on posttransplant growth of vinca (Catharanthus roseus L.). Bare-root seedlings were germinated in a peat-based growing mix and transplanted into diatomaceous earth 10 days after seeding. Immediately after transplanting, seedlings were drenched with several concentrations of IAA or NAA (62.5 mL/plant). Both auxins increased posttransplant root and shoot growth, but the response was dose-dependent. The maximum growth occurred at concentrations of 10 mg.L[-1](IAA) or 0.1 mg.L[-1] (NAA). The growth-stimulating effect of these auxins decreased at higher rates and NAA was highly toxic at 100 mg.L[-1], killing most of the plants. Unlike the growth of bare-root seedlings, plug seedling growth was not stimulated by drenching with NAA solutions. These results show that auxins have the ability to stimulate posttransplant growth of vinca, but their effects may depend on the application method, rate, and timing, and transplanting method. http://cat.inist.fr/?aModele=afficheN&cpsidt=1611451


I find the last two sentences of this conclusion to be very interesting. This further points out my original premise that you must be very careful when trying to extrapolate the results of any experiment to a situation with different parameters.


Here is another study on the exogenous application of NAA on seedlings:
http://forestry.oxfordjournals.org/cgi/content/abstract/63/2/197
However, these are seedling experiments with NAA applications just before and just after cotyledon development. It is generally accepted that root hormones have a strong influence on seedling germination and root development in the first week or two after germination. It is a mistake to extrapolate this to woody plants with developed plants in a transplant situation.

NAA root applications may be of benefit in planting conifers in forestry situations where root development is difficult in native soils:

Primary lateral root production on Pinus contorta seedlings was increased 5–10 fold by immersion in auxin solutions. Watering auxin solutions onto P. contorta seedlings growing in soil or compost induced the development of large numbers of primary lateral roots in the root collar region. The number of primary lateral roots which developed depended mainly upon the auxin used and its application rate, seedling age and to a lesser extent on the soil characteristics. Instability of transplanted pines is partly due to their lack of primary lateral roots and their inability to regenerate new ones after planting out; this instability may be overcome by using auxin treated seedlings. Potential practical applications of this technique are discussed. http://forestry.oxfordjournals.org/cgi/content/abstract/55/2/125
I found one study that concludes that NAA root treatments of a woody plant clearly had no benefit on overall plant growth. This study uses several measures for plant growth, that I think are worth noting.

http://72.14.253.104/search?q=cache...imulate+root+growth&hl=en&ct=clnk&cd=86&gl=us

(scroll down to page 110 to find the effect of NAA)

This study compared the effects of NAA and BA (a cytokinin) separately on the accumulation of CPT, a cancer fighting compound. However, it also measured the effect of NAA on the morphology of the plants including RSR (root to shoot ratio), plant weight, and plant height. The concentration of NAA used was from 0 to 4 mg/L, which is in the ballpark for the concentrations used in the other studies above that showed lateral root development in this range.

The conclusion is:

In conclusion, exogenous BA and NAA applications inhibited plant height and leaf
number of C. acuminata in a hydroponic culture system, and NAA applications also inhibited
plant weight and leaf length. Exogenous BA and NAA applications both increased RSR, and
NAA applications decreased SLW. BA applications significantly increased CPT accumulation,
whereas NAA applications had no effect on CPT accumulation. Conversely, BA applications had
no effect on CPT yield, and NAA application decreased CPT yield

Unlike potential positive effects in compromised environments, the effect of NAA solutions on roots after transplanting must be compared to the strong stimulation that can be effected by several known and accepted procedures as I pointed out above. Not so commonly known is the role of Phosphorus. Myth has it that phosphorus is good for roots and thus should be good for transplants (bonemeal addition to soil prior to planting for example). The actual effect is the opposite:

Plants typically respond to P deficiency by allocating more carbon to roots, thus increasing their root-to-shoot ratio. In addition, low P availability can dramatically alter the spatial configuration of the root system by increasing root hairs and promoting lateral root formation. Such plastic root alterations are believed to play a crucial role in exploring increased soil volumes in search of nutrient-rich patches (Neumann and Martinoia, 2002; López-Bucio et al., 2003). In Lupinus albus, P deficiency promotes the formation of cluster roots, also termed proteoid roots (Johnson et al., 1996). Increased root branching in response to P limitation has also been reported for Arabidopsis (Arabidopsis thaliana). Growth of Arabidopsis in a moderate-to-limiting supply of P results in a redistribution of root growth from the primary to lateral roots (Williamson et al., 2001). Reduced primary root elongation in low P conditions was accompanied by increased root branching, perhaps concentrating root biomass near the soil surface for more efficient nutrient foraging (López-Bucio et al., 2002, 2003

http://www.plantphysiol.org/cgi/content/full/137/2/681

But once again, I have to caution you that you have to consider the overall plant growth before developing a plan of attack. So, if you decide to withhold phosphorus because it promotes strong fast lateral root growth after a transplant, you would have to quickly reverse this to normal nutrient feeding as soon as the roots colonized or nearly colonized the pot to prevent the deleterious effects of P deficiency in other parts of the plant.

Nutrient levels can have a strong influence on root development:

Several soil nutrients can alter root hair development (Reviewed in López-Bucio et al, 2003). Fe or P deficiencies both induce more epidermal cells to differentiate as root hairs, and both induce root hairs to elongate more than normal. These two pathways appear independent. The Fe pathway appears to function through the ethylene and auxin pathways because ethylene and auxin mutants show altered responses to Fe deficiency. P appears to be ethylene and auxin independent. The increased root hairs increases the surface area of roots, increasing their capacity to absorb limited nutrients.
Several nutrients can also alter root architecture by altering lateral root formation or growth, or by altering primary root growth. High nitrate inhibits lateral root elongation if the root system is uniformly exposed. However if only a portion of the root system experiences high nitrate while the rest experiences deficiency, the section with high nitrate will show elongated lateral roots. A MADS box transcription factor, ANR1 is induced by local high nitrate and is required for the root architecture response.
Nitrate supply increase cytokinin content in the root. Takei et al (2004) have shown the adenosine phosphates-isopentenyltransferase AtIPT3 is a key determinant of nitrate-dependent cytokinin biosynthesis in Arabidopsis.
Phosphate deficiency induces the formation of lateral roots and inhibits root elongation. The result is a dense, highly branched root system. This is compounded by the effect on root hairs. In addition, expression of phosphate transporter genes and other physiological changes result in a root system highly adapted for efficient uptake of P. The effects on root growth are brought on by inhibition of the cell cycle and by low auxin concentrations in the root apical meristems.

Sulfate deficiency also increases lateral root density. The NIT3 (nitrilase3) gene is induced and thought to increase auxin synthesis.
Moreover the cytokinin receptor CRE1/WOL/AHK4 has been shown to be involved in the interaction between phosphate-starvation, sugar, and cytokinin signaling in arabidopsis (Franco-Zorilla et al., 2005)
Several lines of evidence suggest the nutrient ions may act directly as signaling molecules. Mutants in nitrate metabolism still show the normal response to Nitrate. Root systems on plants with adequate phosphate show the classic P starvation phenotype in localized areas of deficiency. Thus the changes in root architecture are not secondary effects of altered metabolism, but appear to be primary effects regulated by the ions themselves. http://en.wikibooks.org/wiki/Plant_Sciences:Arabidopsis_root_development

The non uniform nitrate levels is especially interesting. First, this would indicate that high levels of nitrate should be avoided. But also, if irregular location of the nitrate can be achieved, this will increase root growth. This may be possible with pelletized time/temperature release fertilizers. I have been incorporating Osmocote into my soil mixes for years.

Lastly, in one of the studies (unfortunately I can no longer find the citation), it was shown that a single treatment of NAA stimulated the growth of lateral roots, and that subsequent treatments did not stimulate more rooting, and could in fact, inhibit further rooting. This makes sense since the role of NAA in stimulating rooting is to activate the tissues deep within the root to produce lateral roots, but the growth and elongation of the new lateral roots is due to the other factors. This is exactly equivalent to the role auxin plays in stimulating adventitious roots in stem tissue. Here also, a single application is beneficial, but subsequent applications result in no further rooting and may inhibit further lateral rooting.

In conclusion I think we can fairly and safely assume the following from the studies and references above:

NAA treatments can stimulate lateral roots in new seedlings.

Root stimulation is species dependent and in some species may be counterproductive.

Response level is greatest at very low doses with a possible maximum of 0.1 mg/L (equivalent to 0.1 ppm).

Higher dose rates are counterproductive and may even be toxic.

A single treatment is best, additional treatments with NAA do not further stimulate lateral roots or are inhibitory.

Treatment will work best with a moderate amount of nitrate and no phosphorus and no iron.

Continued in next post.......
Brent
 

Brent

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continued from above, too long for one post:

I think this is a fair reading of the literature. To see if there is a real world procedure for using a NAA root stimulant in growing woody plants in container culture will only be proven by a controlled study on developed plants. I did not find such a study and one may not exist. I doubt even then if it would settle the argument, but it would go a long way in demonstrating if such a treatment would be beneficial. First we would have to define the terms of 'beneficial'. I can see two measures that might fit our particular form of container culture. The first would be survival rate. I have my doubts about this as a measure since in properly cared for nursery plants, 90 to 100% normally survive the root pruning and transplant procedure, but it can be an indication if numbers vary far from normal survival rates.

Growth rate in most of the studies I read is measured in several ways. One method is RSR, or root to shoot ratio. This is measured by weighing the roots and the top of plants independently. A high ratio would indicate more root growth than top growth. In a transplant situation that may seem to be ideal, but is it really? Which is more important, fast colonization of the roots at the expense of shoot growth, or faster shoot growth that eventually leads to a greater total plant weight? As long as the plants are otherwise healthy and the survival rates similar, I would be inclined to accept the higher total plant weight as a measure of success over a higher RSR. This would have to be decided.

I have been threatening to do this for years, so perhaps now is the time. I don't propose to do a tightly controlled scientific study; one reason is that I am not about to sacrifice my plants to do a dry or wet weight measure. But I think we can get around this. I could do a double blind study where I have someone mix up two solutions, one with NAA at 0.1 mg/L and the other plain water (or use Superthrive that would give this concentration if the relevant information is on the label). I would not know which solution contained the NAA, and the person doing the mixing would not know which plants I treated with which solution.

Getting uniformity is the most difficult part in a test for effects on transplanting rather mature material, since that is what we use in bonsai, not seedlings. Fortunately I own a nursery. I have several hundred six year old Trident maples, Acer buergerianum, still in 2 ¾ inch pots. These are beginning to show signs of stress and are becoming rootbound. This winter, most of these will be root pruned to give them a good radial network and then shifted to 4 inch pots. This is a rather massive root pruning; perhaps 80% of the roots will be removed. Typically 90% or more of these should survive.

I could divide the flats of 4 inch pots (16 pots to the flats) and use at least 2 flats of plants for the treated test and 2 flats for the control (or more). Using this many plants would give a good average weight. The soil and pots are very uniform. Each flat could be weighed periodically. This of course would also weigh the pots, soil, and water, but if they were all weighed one half hour after watering, these factors should all be the same. Any differences between the groups should be a difference in total weight of the plants. I could also make observations about the height of the plants at intervals. I could probably do this through next summer until the plants would have to be pruned, by which time any differences would be evident, and any further benefit doubtful.

I would use my standard soil, and standard fertilization techniques, since if there is a benefit, it should be evident and useful in a typical nursery environment. The flats could be rotated on a weekly basis to eliminate any preferential benefit of light, air, or water. I can't promise I will actually get around to doing this, but it is tempting since I am tired of typing these kind of posts.


What about collected plants?

Evaluating any potential beneficial effect of NAA solution on collected plants ramains problematic. Collected plants are definitely not like seedlings nor are they similar to nursery plants. They have their own set of problems related to what I believe are 'pathway' constriction issues as I pointed out in the earlier post. There is basically no way to do a controlled study on collected plants because no two are the same. Even deducing any useful information from anecdotal observations is unlikely given their individual diversity and tenuous hold on survival. There will always be good years and bad years for plant survival, but even if you get better survival rates on average over the years, is it attributable to your developing horticultural skills or to a root stimulant? There is no way to tell for sure. The best I could recommend is that a root stimulant would probably do no harm within the parameters I set forth above. However, NOT following the ranges and limits above could clearly damage the plants.

However, while doing this research, I did discover some things I didn't know about root development, and these may have some benefit for collected plants. So, it will be interesting to see if anyone adopts any of this new information, with or without NAA applications. Perhaps, I'm wrong and there will be some clear breakthrough in getting the survival rate of collected plants to a much higher level.

Brent
EvergreenGardenworks.com
see our blog at http://BonsaiNurseryman.typepad.com
 

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