interesting study on cloning

[Elmer Bud]

Awesome to see real research on this subject, especially at Universities. Greatly appreciate you posting this.

The quick takeaway for me is to quit clipping the leaf tips of my cuttings (lowers success rate), and to cut down on the number of leaves instead (reduce transpiration requirements). Differences between 2 and 3 leaf clones were quality of the roots.

Thanks again.

G `day DC aka TCG

The devil is in the detail ...
They had control over humidity . They increased light during the experiment to encourage photosynthesis .

They used a large enough space no plants were touching each other .

If the leaf tips touch the medium or each other the chances of successful rooting decrease . As mold is encouraged .

Thanks for sharin

EB .

 

[Somatek]

Hey just quickly on this the point of introduing drought stress in the study was based on well known science that drought stress increases oil production in medicinal crops so the hypothesis began at by inducing drought stress it is feasible we can increase THC etc percentage in cannabis.


i.e. from paper


Drought stress is a major stimulator of secondary metabolites in plants. This is exemplified in herbs and spices cultivated in semi-arid regions such as the Mediterranean. Intermittent drought 89
and high solar radiation in these areas has been attributed to aromatic herbs and spices with abundant essential oil (Kleinwächter and Selmar, 2015). In the literature, there are no reports on the effects of drought stress in cannabis; however, secondary metabolite accumulation due to drought stress has been documented in a number of other herbaceous species (Baher et al., 2002; Bettaieb et al., 2009; Kleinwächter and Selmar, 2015). In Summer savory (Satureja hortensis), plants that were highly drought stressed during the flowering stage had 31% higher essential oil concentration than a well-watered control (Baher et al., 2002). Likewise, drought stress increased essential oil concentration in lemon balm (Melissa officinalis L.) and lemon catmint (Nepeta cataria L. f. citriodora) compared to a well-watered control but did not for sage (Salvia officinalis L.). Though concentrations were higher, essential oil yield (by growing area) of lemon catmint and lemon balm was lower in the drought-stressed plants because of reduced growth and harvestable plant material.


Another hypothesis they wanted to test was: "Drought stress timing is also essential to minimize yield losses and maximize essential oil yield and the concentration of secondary metabolites; differences in growth stage and natural timing of phytochemical accumulation must be considered by species (Petropoulos et al., 2004)."


Finding was


Yield and cannabinoids
Yield in the control was 178 ± 9.4 g·m-2 and was 232 ± 18.5 g·m-2 in the drought treatment but yield did not differ statistically between the two treatments (P = 0.06; n = 3). The moisture content of the dried and cured floral material was 8 ± 0.1 % in the control, 11% lower than that in the drought treatment, at 9 ± 0.1 % (P = 0.01; n = 3). Henceforward, the floral dry weight and cannabinoid contents are corrected to zero percent moisture.
Of the analyzed cannabinoids, all were detected in at least one sample, these included: THC, THCA, CBD, CBDA, CBG, CBGA, and CBN. In the drought treatment, only one sample had a detectable concentration of CBG and CBN, and in the control there were no samples with detectable CBN; therefore, comparisons could not be made for these cannabinoids, and the means for CBN were not presented.
The drought treatment elicited a 12% increase in THCA concentration and a 13% increase in CBDA concentration but had no effect on the concentrations of the other detected cannabinoids
98
(Table 5.3, top). Drought had substantial effects on cannabinoid yield, expressed as grams of cannabinoid from floral material per unit growing area (g·m-2). In the drought treatment, THC yield was 50% higher, THCA yield was 43% higher, CBD yield was 67% higher, and CBDA yield was 47% higher than in the control (Table 5.3, bottom).


Conclusion equals


Discussion
The controlled drought treatment used in this study substantially increased the concentrations of both major cannabinoids, THCA and CBDA as well as yield of THCA, CBDA, THC, and CBD compared to the control. These results suggest that the level of drought stress applied in the present study was adequate to stimulate cannabinoid production without reducing yield for this cultivar.


So no the hypothesis that drought stress could be used to improve oil yields was demonstrated. Also the hypothesis that if drought stress was implemented correctly yield losses (re harvested dried product) may not result was also demonstated.


Look over the paper more carefully - I think you might find you've misread/misinterpreted the data.. I wanted to go back to it myself to look more closely before commenting further.

Which paper is that from as I didn't see it in either the Stemeroff or Caplan ones linked. Caplan states in the discussion/conclusions under draught stress

"Controlled drought influenced the content of some cannabinoids and terpenoids, as demonstrated in chapters five and six of this thesis. Using leaf wilting as a drought stress indicator, with fertigation triggered at a leaf angle 50% higher than in its turgid state, proved to be effective and easily measured.
There was a notable difference in the effect of drought on cannabinoid content between chapters five and six. In chapter five, drought during week seven increased the content of some cannabinoids compared to the control, whereas there was no increase in the week-seven drought treatment in chapter six. We speculate that differences in flowering-stage pot size between the trials influenced the duration of the drought stress period and therefore led to variable physiological and biochemical responses in the plants. In chapter five, the pots were 11 L in volume while in chapter six, they were 6 L. A longer, likely more gradual, drought stress period possibly provided by a larger pot may, therefore, be required to increase cannabinoid content in cannabis. This provides another example in which the IRM approach may have been practical. Pot size generally dictates substrate volume which influences a host of interconnected root zone
parameters. Attention is required to anticipate how root zone parameters will be affected when
one aspect such as pot size is changed. Further research is needed to determine the effects of pot size and duration of water deficit on cannabis secondary metabolism and to explain the physiological changes during drought that bring about these effects."

Which is the nuance I'm refering to, it's not like any water stress resulted in an increase of cannabinoids, the results are varied between the papers and illustrate a need for more research to understand the nuances of what's going on. What was consistent is the significant reduction in water usage without any noticeable difference on yield/quality, so purely from an economic/environmental perspective it's better to slightly underwater.

 

[BongFu]

Which paper is that from as I didn't see it in either the Stemeroff or Caplan ones linked. Caplan states in the discussion/conclusions under draught stress

"Controlled drought influenced the content of some cannabinoids and terpenoids, as demonstrated in chapters five and six of this thesis. Using leaf wilting as a drought stress indicator, with fertigation triggered at a leaf angle 50% higher than in its turgid state, proved to be effective and easily measured.
There was a notable difference in the effect of drought on cannabinoid content between chapters five and six. In chapter five, drought during week seven increased the content of some cannabinoids compared to the control, whereas there was no increase in the week-seven drought treatment in chapter six. We speculate that differences in flowering-stage pot size between the trials influenced the duration of the drought stress period and therefore led to variable physiological and biochemical responses in the plants. In chapter five, the pots were 11 L in volume while in chapter six, they were 6 L. A longer, likely more gradual, drought stress period possibly provided by a larger pot may, therefore, be required to increase cannabinoid content in cannabis. This provides another example in which the IRM approach may have been practical. Pot size generally dictates substrate volume which influences a host of interconnected root zone
parameters. Attention is required to anticipate how root zone parameters will be affected when
one aspect such as pot size is changed. Further research is needed to determine the effects of pot size and duration of water deficit on cannabis secondary metabolism and to explain the physiological changes during drought that bring about these effects."

Which is the nuance I'm refering to, it's not like any water stress resulted in an increase of cannabinoids, the results are varied between the papers and illustrate a need for more research to understand the nuances of what's going on. What was consistent is the significant reduction in water usage without any noticeable difference on yield/quality, so purely from an economic/environmental perspective it's better to slightly underwater.

Ah that could explain it..... Full PhD thesis available here https://atrium.lib.uoguelph.ca/xmlu...n_Deron_201808_PhD.pdf?sequence=5&isAllowed=y

Drought stress at page 103 onwards...

 

[BongFu]

G `day DC aka TCG

The devil is in the detail ...
They had control over humidity . They increased light during the experiment to encourage photosynthesis .

They used a large enough space no plants were touching each other .

If the leaf tips touch the medium or each other the chances of successful rooting decrease . As mold is encouraged .

Thanks for sharin

EB .

All that said I would see it as a fail to get such low strike rates..

 

[f-e]

The professional approach to making the comparisons is what gives weight to this study. It's just a single study though, and one variable is still left to be compared. They only used one team of growers, who seem to be under performers. It's our job to compare their results to those of others. In our continuing study of the subject.

I will steer away from leaf trimming then. I try where possible to remove entire blades, but will aim for entire formations. It can't do any harm.

 

[TrickEE]

Great info everyone and the original poster. I always love learning more about the plant we all love. I have been watching episodes of The Dudes Grow Show podcast, and there is a bunch of great info on there as well as great interviews with people within the cannabis industry. Give it a listen if you have some extra time. Healthy nugz.