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misc Scientific Observations of Environmental Stress on Pepper Varieties

There are a lot of studies out there, and many of them conflict. Some say stress makes hotter, some say consistency. Some say smaller peppers benefit (?) the most from stress, others says larger. Yet again, one study suggests lower pungency benefits (?) more from stress, and another study flatly contradicts that. Some use large sample, some use small.

I don't know if there will ever be a true concensus on this. I know that when I grow plants, I strive for optimum growth and productivity, and when I need something hotter, I find a variety that does that for me. Whether it's outdoors, indoors, neglect or care... I can ALWAYS grow a pepper that's hotter than what I can eat. As somebody else noted, my early peppers aren't always on point, but later on, they come good, and stay good for the entire season.
 
http://hortsci.ashspublications.org/content/43/5/1549.full.pdf
 
Here is another paper that adds to this topic- they found that nitrogen was the biggest driver in increasing capsicum in habaneros.
 
Influence of Nitrogen and Potassium Fertilization on Fruiting and Capsaicin Content in Habanero Pepper (Capsicum chinense Jacq.)
 
Habanero pepper (Capsicum chinense Jacq.) is a very important crop in Mexico and demand for it is increasing in national and international markets. The habanero pepper produced on the Yucatan Peninsula is considered of superior quality to that grown in the rest of the world as a result of its shelf life and pungency. Despite its importance, little research has been done on cultivation conditions that may affect its productivity and fruit quality. The effect of N or K fertilization on habanero pepper development and fruit pungency was evaluated. Plants under fertilization stress (control) had high capsaicin content. Nitrogen fertilization significantly increased plant growth and fruit while maintaining high capsaicin levels. Optimum response was produced with 15 mM urea as the N source. Potassium fertilization had no positive effects on growth or productivity. The N treatments modified endogenous K levels in the pepper plants and vice versa. The K : N ratio (specifically in leaves and roots) varied between treatments with values greater than 1 in the K treatments, near 0.5 in the control, and less than 0.5 in the N treatments. This parameter may be an important indicator of habanero pepper productivity and requires study under different fertilization regimes.
 
 
 
Maybe this will put to rest that you need to reduce N when fruiting....
 
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Nutrient Stress AND Proper Fertilization With N Provide the Highest Capsacin Levels
 
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thefish said:
Maybe this will put to rest that you need to reduce N when fruiting....
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I love your optimism, but you underestimate the power of misplaced faith in traditional knowledge.  Say it after me... "that is how we've always done it..."  "That is how we've always done it..." "That is how we've always done it..."
 
solid7 said:
 
 
I love your optimism, but you underestimate the power of misplaced faith in traditional knowledge.  Say it after me... "that is how we've always done it..."  "That is how we've always done it..." "That is how we've always done it..."
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Look at the table I posted. Pretty convincing result. No fertilizer produced the hottest peppers but the lowest yields. Potassium was all but useless in promoting flowering or fruit set. Both increasing potassium and reducing nitrogen are often recommended as interventions to get fruit to set. Its clear that you can get hotter peppers via modulating the environment... but at what cost? Many plants flower when they are happy and ALSO when they are on the brink of death. Its not surprising that peppers have developed the response to boost capsaicin when under stress because it probably adds a little insurance that the few pods they produce when on the brink of death wont be eaten by mammals. I'll keep my peppers happy and well fertilized because as long as I'm not over doing I'll get nominally less spicy peppers but massively bigger yields.
 
You already know that you and I are kindred spirits, man...  I have known for a very long time that we don't cut off Nitrogen, and I'll preach that until the day that I stop growing.  If one is getting close to missing out on a season of peppers, I'd say that it's OK to drop Nitrogen temporarily, but I'll never advocate increasing Potassium. (unless it's actually needed due to deficiency)  And then, right back to normal Nitrogen.
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I am interested in this other product.  But I'm wondering what the drawbacks to using it might be.  Anything to add?
 
What about light stress? Exposing chilies with different UVA/UVB density. I have not seen a single discussion about it. Could it possible to increase capsaicinoids? I would like to see field test of it. 
 
There are tons of variables that none of these studies seem to comprehensively consider. They are almost all conducted in singular locations with specific environmental variables.  A test like this has so many dimensions, that it would really take a litany of tests and research documentation to arrive at a solid conclusion.  This kind of ag research is great for arriving at regional conclusions - but it's not meant to be consumed by the backyard grower.  Even more so, if said grower doesn't reside in the test region. (assuming that the research isn't lab based)
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When big Ag conducts genetic and hybrid research, samples are sent to regions all over the globe, and the data is gleaned from a systematic comparison - and often, refined for, and through, later testing.
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I think if hobbyists really wanted a definitive answer, they'd start as an open source experiment, in an INDOOR grow.  There'd still be some expense involved verifying results, and it would require that everyone involved, be diligent in documenting their parameters.  But I don't think that you're too likely to be able to proceed to conclusive outdoor results, until you get some concrete control data, first.  The hypotheses that surround capsaicin production, in my humble opinion, need to be refined greatly, based on something other than regional data.  I have grown in every region of the US, aside from Hawaii and Alaska.  The differences from place to place are STARK.  They translate into tangible differences in final product.  No single variable separates one region from another.
 
solid7 said:
There are tons of variables that none of these studies seem to comprehensively consider. They are almost all conducted in singular locations with specific environmental variables.  A test like this has so many dimensions, that it would really take a litany of tests and research documentation to arrive at a solid conclusion.  This kind of ag research is great for arriving at regional conclusions - but it's not meant to be consumed by the backyard grower.  Even more so, if said grower doesn't reside in the test region. (assuming that the research isn't lab based)
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Well I did the best I could. I found one that covers soil type - different location - nutrients:
 
Impact of nutrient management, soil type and location on the accumulation of capsaicin in Capsicum chinense (Jacq.)
 
Even dabbles a bit in vermicompost, that's one of your specialties, isn't it?
 
The_NorthEast_ChileMan said:
 
Well I did the best I could. I found one that covers soil type - different location - nutrients:
 
Impact of nutrient management, soil type and location on the accumulation of capsaicin in Capsicum chinense (Jacq.)
 
Even dabbles a bit in vermicompost, that's one of your specialties, isn't it?
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I wasn't knocking you.  This is a share forum, and you did just that.  I'm just saying that as far as research goes, this type would be fairly low priority, unless you were in the business - and then you'd follow the advice that was developed in your region, for your specific market. 
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My reply was really directed at Karpasruuti.  There are tons of variables that go into growing.  To be honest, I've never eaten a chile in Finland, so I don't know if they are even as hot as a Florida chile, for instance.  So that's another thing.  And each species has a stated range - which, if we're being honest, we don't even really know if it's accurate.  But even within the range, there's a huge variation.  We can really only go by the baseline Scoville number that was established at the time of the test. (which costs money, so it probably doesn't get re-tested often)
 
In short, I'd love to see an epic research project on this subject - but I just think that it would be incredibly difficult, and even more costly.  I hate to be pessimistic on the subject , but I just think  that if this kind of information is only ever going to come from chile growing people.  Open source would be great - but the truth is, it takes a lot of discipline to research something like this so thoroughly.  I have a highly technical background, and even write white papers for various subjects - but research is in a whole other category.  Those are highly specialized personalities.  But still...  If we could get a dozen research oriented people, from several us regions, and about 30 more the represent different regions around the world, I think you'd get a pretty damned good answer to the eternal question.
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Of course... You'd have to research species by species, and...  that gets complicated really fast.  
 
This type of all-encompassing research is quite rare in the academic field, because each lab tends to have its own type of specialisation and objectives (and sometimes, sponsers). The kind of information you would like to see is typically published as a review paper, where a researcher (or group of researchers) evaluate the published literature and compare and/or summarise the known data. In this type of publication, you could (in theory) a comparison of growing conditions for habanero in Yucatan and Sierra Leone... Or academic books, which lately have often become multi-author enterprises.
 
ahayastani said:
This type of all-encompassing research is quite rare in the academic field, because each lab tends to have its own type of specialisation and objectives (and sometimes, sponsers). 
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This is a very good observation of "research" as bolded-underlined above. As noted in the title of this thread, Scientific Observations of Environmental Stress on Pepper Varieties, my original intent was to look at scientific papers that addressed this influence as it is often mentioned and just as often questioned, especially lack of watering stress. You'll note in my original post that I listed links that had different results from others on this subject.

As always, YMMV...,..
 
Thank you all for interested of the subject. I don't have myself knowledge, time or the stuff to measure capsaicins and other factors to make anything scientific value. But I could still make subjective test is A or B hotter than C controlled and what I was doing different. Also I don't have space for that many plants to grow. Also the spectrometers are expensive cost more than 500 bucks.
 
The_NorthEast_ChileMan said:
 
You'll note in my original post that I listed links that had different results from others on this subject.
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Which I think you'll agree was a follow on to one of my previous assertions.  For every claim of capsaicin increase in X condition, there was some other study that said otherwise.
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This subject, like many other things in hobby growing, is characterized by an idealistic pursuit, predicated on the misapplication of specific research.  Not that it's bad to have discussions - but with nothing more than we have to work with, that's all we're doing.  To be clear, I'm just trying to say that there is no "one size fits all" answer to the capsaicin question.  Discussions pave the way for real research, of course.  But for the here and now, everything on the subject is anecdotal, at best.  Unless you're lucky enough to be growing in the Hatch Valley.  I'm pretty sure they have their methods down solid.
 
solid7 said:
Which I think you'll agree was a follow on to one of my previous assertions  For every claim of capsaicin increase in X condition, there was some other study that said otherwise.
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Yes it was, from three years ago (Note dates in below.). 
 
solid7 said:
There is actually more science to validate the notion that a plant that is provided a constantly optimal growing environment, will outproduce on every level.  Taste, heat, yield, health, etc.
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The only possible exception would be lower heat plants.  There have been SOME studies that suggest a link to stress and increased heat levels.  But side by side studies with milds, hots, and superhots, only suggest a small difference on the lower heat varieties..
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To which I asked:
 
The_NorthEast_ChileMan said:
And a link to just 1 of these scientific studies?
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.....................................................................Still waiting................................................
 
The_NorthEast_ChileMan said:
 
Yes it was, from three years ago (Note dates in below.). 
 

To which I asked:
 
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.....................................................................Still waiting................................................
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Oh, no, I am not going to re-tread that subject.  I have in the past, posted links to studies on the subject, but my conclusion after reading too many studies, and doing my own grows, is EXACTLY what I've just posted.  In case you missed it - post a study that confirms one conclusion, somebody else will have a study that either fails to confirm, or contradicts the previous.  Why do I need to do that, when you've already shown that point?  And I've also show it in the past.
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I'm not sure why you want to add more to this than what's added. On the capsaicin topic, this ends up being a stalemate, any which way.  
 
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