Increasing Weight and Cannabinoid Content Using Drought Stress

[anon32470837]

@Northern_Loki

The Licor Photosynthesis Analyzer or the PhotosynQ are tools that could help determine the point of stress.

Im not clear on exactly what they measure or how. It sounds like they basically look at the leaf transparency, or do they actually take a sample in some way, or? I have to admit I stopped looking into them both when I saw the price.

In any case, I suspect both are well beyond what most of us would be willing to pay. Me for sure

Edit: I know there is a lot of interest in this as a possible new growing technique. Do you happen to know of any way short of those $$$ instruments - for the rest of us to determine how far to go?

I can see this easily turning into the newest rage in “cutting edge” techniques, but with zero science behind a ton of new DIY newage methods being promoted on YouTube - all of which are guaranteed to increase your yield if you are just smart enough to follow some simple instructions and LIKE the video

[Northern_Loki]

They essentially measure the parameters of photosynthesis and efficiency using chlorophyll fluorescence.

From PhotosynQ:

it measures fluorescence base parameters like qL, qP, ΦII, LEF, NPQ, and absorbance based parameters like vH+, gH+ ECSt and relative chlorophyll content. It can collect environmental parameters like temperature, relative humidity, barometric pressure, leaf temperature, light intensity, cardinal direction and tilt.

PhotosynQ is ~1K (commercial users). Those tools are useful for those engaging in a study but also can be useful for a number of reasons.

Yes, you can do these type of measurements DIY but you’d be looking at a lot of time getting it right and producing accurate data.

Plant stress measurement

Some example applications for such measurements (just a quick search for “SPAD stress”):
agronomy-07-00061-v3.pdf (678.8 KB)
water-11-00586.pdf (2.3 MB)

SPAD-based leaf nitrogen estimation is impacted by environmental factors and...

[Sincy]

There is so much research that needs to be done it’s just the tip of the iceberg. There is just enough information at the moment to get people into more trouble than success. I think that container style plants are much more forgiving than hydro or aeroponic systems. I tried this with my organic soil plants and it took a week for the soil to dry enough to affect the plants. I allowed them to wilt for 48 hrs before I watered at the end of the seventh week of flower. I was more interested in using this to maybe make better seed since there seems to be an increase in plant metabolism and immune system activity. There is alot of possible with this but I think it will be a while before we get some more definitive information so I would practice caution and play around with a plant to the side before trying it on your whole crop.

[Northern_Loki]

@Sincy

I would practice caution and play around with a plant to the side before trying it on your whole crop

Some of us (ahem, Larry), seem to take pride in punishing the produce

@Sincy

There is so much research that needs to be done it’s just the tip of the iceberg. There is just enough information at the moment to get people into more trouble than success.

Believe it or not, I’d suggest a good deal of the studies and insights are derived from the random theories and experiments produced by some of the most fanatical crop growers (e.g. all of us). Sometimes we understand what we are doing correctly, sometime we are completely off our rocker. But when correct, it spurs more innovation and builds a collective base of knowledge we can refer back to. So, meh, trouble? I just learned something.

@anon32470837

I suspect both are well beyond what most of us would be willing to pay.

FWIW, I bought one for continuation of the dissolved oxygen experiments. Aka, cognitive disorder study.

[Sincy]

Episode #57 of Cannabis Cultivation and Science podcast is an interview with Dr. Caplan the first person in North America to earn a degree in cannabis cultivation. I’m not advertising for them but this is a really interesting interview and much easier than reading his paper that is pretty involved and covers all this drought stress information.

[ReikoX]

I’m still stuck on N=8 and a single cultivar. They mentioned several times in the article that is it cultivar specific. Sorry, I work in the scientiltific community, so these things bug me.

[valleymicro]

Thanks for the podcast info @Sincy. Listening now.

I agree @ReikoX. Not large enough of a sample size but interesting results. I think @anon32470837 is right and this should be expanded to a larger sample size and maybe different cultivars. Who will take on this mission? I don’t think commercial operations that are setup to support this are interested in scientific experiments at this point. And research teams are limited in growth space/technology.

Great comments from the OG community as usual. I’m learning a lot just from the responses.

[anon32470837]

@Northern_Loki

Some of us (ahem, Larry), seem to take pride in punishing the produce

LOL!! I am going to start calling myself the ‘Accidental Scientist’ and make all sorts of claims for my ‘research studies’. Or maybe the Accidental Torturist? Not sure what claims I could make with that title though.

@Northern_Loki

FWIW, I bought one for continuation of the dissolved oxygen experiments. Aka, cognitive disorder study.

Dang it! You have all the best toys!!!

[Heritagefarms]

I would bet it is more beneficial to certain strains then others. The oils are more of a barrier to the heat and uv then to prevent evaporative loss. They help keep the surface temps down so the plants metabolism can function properly. It’s like sunscreen in a way.

[Northern_Loki]

Some more info on detecting drought stress by measuring photosynthesis:

As with nutrient stress, water and salinity stress cause changes in virtually all physiological systems in the plant. Potential of roots to absorb nutrients generally declines in water-stressed plants, presumably because of a decline in nutrient demand. Concentrations of photosynthetic enzymes decline in response to drought, as does photosynthetic rate (Kluge 1976).

…mild drought stress causes carbohydrate concentrations to increase (Hsiao et al. 1976). Second, the decline in leaf growth preceeds the decline in dry weight accumulation (Munns et al. 1982, Wardlaw 1969). Together these observations indicate that drought causes a reduction in growth most directly by altering hormonal bal- ance, but that associated with this decline in growth are interconnected changes in plant nutrition, carbon balance, and water relations.

While observing:

…plants exhibit a centralized system of stress response that can be triggered by a diverse range of stresses. This centralized stress response system is hormonally mediated but involves integrated changes in nutrient, water, carbon, and hormonal balances of plants.

Integrated Response of Plants to Stress (Chapin III) 10.2307@1311538.pdf (1.8 MB)

[anon32470837]

@Northern_Loki

the decline in dry weight accumulation

@Northern_Loki

indicate that drought causes a reduction in growth

Those two statements seem to contradict the original study using the 8 pot plants.

[Northern_Loki]

Was mainly pointing out how to detect stress, not certain about the correlation of dry weight between the two papers. The op’s paper does note:

inflorescence dry weight did not differ statistically between the two treatments (P = 0.06; n = 3)

Also, I think inflorescence refers to the flowers specifically. The posted study on stress may be measuring something different as the whole plant dry weight. Not entirely clear to me.

[ReikoX]

Thanks for the useful information. It at least gives us some clue how we could monitor drought stress.

@Northern_Loki

inflorescence dry weight did not differ statistically between the two treatments (P = 0.06; n = 3)

What happened to the fourth plant?

[GMan]

It seems like you would have to run the same cultivar multiple times at a certain set of parameters and then do multiple grows of the n=8 again all at different parameters…

And, then grow multiple cultivars the same way to further the understanding of it… ?

I believe that stress on some level does change the game. But, that’s just from some of my personal observations and not from studies.

[Ghostfarmer420]

I have noticed increased yield and potency from drought stress, in fact I have made out door ghost OG look similar and taste similar to indoor Ghost OG with accidental drought stress. I believe that when the plant spends energy searching for nutrients and water, then receives it as a reward for its exercise it makes the best use of the molecule. much like a runner needs fats and carbs because they tend to be lean, I understand mammals and plants have little in common however the mechanism that created both evolution.

[anon32470837]

Hi @Ghostfarmer420! Welcome to OG

[Ghostfarmer420]

Thanks brother, looking foreword to the conversation

[Ghostfarmer420]

plants that live constantly wet have generally less turpine production. as stated on the General hydroponics web site. I took this to mean that recirculating and DWC though some of the fastest growing methods are fundumentally flawed.

[Ghostfarmer420]

Getting my plants to weep occasionally for short periods of time (hours) is a part of normal growing at this point in my garden. I do this 3 times during bloom usually one week after i notice a significant hormonal change for Ghost OG its weeks 3 7 9. To dry mine from running off water to drought only takes 24 hours.

[Heritagefarms]

I would agree my friend that did deep water culture grew terpless weed in comparison to my flood and drain that was able to dry out periodically. Ghost og is a favorite of mine btw would love to see some pics to compare to the ghost cut Im holding