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Since black walnut trees affect the plants growing around them, do the yields of more tolerant plants have yields affected by the toxin to produce less?

black thumb
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Does juglone (an allelotoxin from black walnut) affect (positively or negatively) the yield of juglone tolerant crops?

Look into allelopathy... it's talked about in this SE as well as around the internet. I'm certain that this is a long winded answer with lots of examples. In general, allelotoxins affect the field like the desert provides a life for cacti. Without the desert, cacti would be out-competed by other plants. Although I would expect that very few plants would be positively affected by juglone, I'd bet that there are a few... besides other walnut trees... perhaps parasitic plants like trumpet vine would be stimulated in the presence of juglone (I asked myself this question years ago as I was considering how well the trumpet vines were growing on the walnut trees in my area).

Allelotoxins, like juglone from black walnut and sorgolene from sorghum, have been studied for many years to improve crop yields with rotation and companion planting- and for making herbicides- and for other discoveries. There are some new herbicide products on the market derived from the research.

Juglone especially affects tomatoes and solanaceous plants.

Here is a good read about Juglone: A SUMMARY OF EXTRACTION, SYNTHESIS, PROPERTIES, AND POTENTIAL USES OF JUGLONE: A LITERATURE REVIEW

Ben Welborn
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  • Really? I thought that Juglans nigra and many other trees did this on a regular basis so as not to have to compete with their progeny. Why would this toxin be harmful to the solanaceae group? I gotta go check you out...are you an organic chemist??? – stormy Jul 16 '16 at 22:46
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    @stormy here's a link about [juglone toxicity toward solanacea](http://www.extension.umn.edu/garden/yard-garden/trees-shrubs/toxicity-of-black-walnuts-towards-other-plants/)... but there are many. It is a well documented observation/fact. The reason is for competition is practically the story of life. I've never heard about the toxicity of juglone toward othewr walnut trees (or progeny)... seems counterintuitive, but still plausible; stuff like that happens- biology is ironic and harsh. Do you have a report about juglone toxicity against other walnut trees or progeny? – Ben Welborn Jul 17 '16 at 15:41
  • Ben! I just went to LOOK AT YOUR profile and wow...a Jack of a hell of a lot of great trades! A chemist! Hands on landscaping! And and and...my goodness, how exciting. I'll go check your link out and check on a few things I need to bone up on and I shall be bugging you an awful lot! – stormy Jul 17 '16 at 19:54
  • Well, there must be something to the fact that BOTH these genus are some of the most toxic of plants! If I were to do a study I'd want to see how the two different toxins interact. How fascinating that the Walnut wants or needs to eliminate Solanaceae! I was taught that Walnuts and other trees (gotta go remember which trees) produce toxins to eliminate competition from their 'progeny'...to also include Solanaceae is a head-tilter! Working with walnut to make furniture or whatever is a big deal! Is there are difference between the two toxins? – stormy Jul 17 '16 at 20:06
  • @stormy Juglone and sorgolene are different chemicals, but they both contain something like a benzoquinone (di-ketone) moiety. So they may act in a simiar manner. Bayer has been working with tri-ketones based on allelopathy research (triketones are little different, but perhaps similar in effect) to inhibit 4-Hydroxyphenylpyruvate dioxygenase (HPPD) an enzyme which catalyzes the catabolism of tyrosine. Excess tyrosine stunts plant growth. Mechanism: the plant suffers from oxidative damage due to lack of tocopherols (vitamin E), so chlorophyll is destroyed due to lack of protective carotenoids. – Ben Welborn Jul 18 '16 at 15:31
  • I have never heard how the chemistry works...so. This would make more sense if these chemicals killed ALL plants that might compete with the tree. Not just walnut babies and solanaceae plants, right? You are saying that if a seed of Sorbus acuparia or even a carrot seed landed within the walnut's environment, it couldn't germinate or if it gets going it will still be killed by Juglone? (the tree puts out this chemical past its drip line?) Or is Juglone only toxic to walnut babies and solanaceae? – stormy Jul 18 '16 at 19:01
  • @stormy juglone is a toxic chemical (to plants and animals). Some plants are more tolerant of toxins (that's natural selection for ya). Juglone probably affects almost all plants negatively, except for the plants that are able to avoid or deal with the toxicity... there could be countless mechanisms for that. I would tend to believe that Juglone was less toxic to walnut babies (otherwise they would hurt themselves)... but I don't know this for sure. Juglone should be more toxic to plants that depend on the enzyme HPPD, or that don't have mechanisms for protecting themselves. – Ben Welborn Jul 18 '16 at 19:33
  • @stormy regarding the strength of juglone, I planted a tomato under a big walnut tree... it grew, but I suppose it would have grown better without the walnuts. So, I don't consider juglone to be a super herbicide... but then again, I suppose that if enough was present it would be lethal. It's just a matter of levels. Moderation seems to be more successful in the long run (says mother nature)... insect resitance to dylox and weed resistance to glyphosate are prime examples of how strength can become a weakness. – Ben Welborn Jul 18 '16 at 19:51
  • Ben, what is HPPD? How the heck were you able to grow a tomato within the toxic boundaries of a walnut? And insect/plant adaptation to chemicals is part of what plants do...I would love to understand what you mean that insect resistance to dylox and plant resistance to glyphosate is a strength...turning into a weakness. Walnuts would only put out a toxin powerful enough to kill walnut babies, not themselves. But that all makes sense. – stormy Jul 19 '16 at 01:51
  • @stormy triketones (herbicides developed from allelopathic research) inhibit 4-Hydroxyphenylpyruvate dioxygenase (HPPD). Juglone is a diketone (a bit less powerful than commercial herbicides), and the amount expressed by walnuts is low enough to grow tomatoes... (and tomatoes are the most sensitive plants to juglone). So, walnut trees express juglone (a fair inhibitor) in moderation. Mother nature has seen fit that moderation is successful in the long run... not bombarding the environment with tons potent pesticides (strength)... which apparently backfires in mere decades (weakness). – Ben Welborn Jul 19 '16 at 12:29
  • @stormy I have been looking for a report about juglone toxicity toward walnut saplings... I can't find anything suggesting that walnuts are sensitive to juglone. I'm not saying that it's wrong, but can you cite anything to support that? Personally, I have seen a fair number of walnut trees sprouting and growing in the vicinity of other walnut trees, but again, I grew a tomato under a walnut (about 25 years ago- when I first learned about alleopathy) just to see the effects. Now I'm thinking about ordering or extracting some juglone... – Ben Welborn Jul 19 '16 at 12:41
  • That HPPD word just rolls off the tongue. Funny, kinda late if you've not got your tomatoes, potatoes in place, grins! I shall go take a peek on the internet. Juglans is so toxic that stringent procedures are followed to the letter when savvy carpenters use walnut. My 'Library' is in storage and I feel so lame without it, sighs! Master Gardeners build a file of official publications and I clearly remember that there are trees, walnuts for sure that put out toxins to kill any progeny competition. Usually the longer lived trees employ this tactic, makes sense. I'll be back, too curious!! – stormy Jul 20 '16 at 06:34