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interesting study on cloning

ramse

Active member

dank.frank

ef.yu.se.ka.e.em
ICMag Donor
Veteran
ABSTRACT
This study evaluated the influence of the several factors and their interactive effects on
propagation success using stem cuttings of cannabis (Cannabis sativa L.). Factors included:
(i) Leaf number (two or three)
(ii) leaf tip removal (1/3 of leaf tips removed)
(iii) basal/apical position of stem cutting on the stock plant, and (iv) rooting hormone (0.2% indole-3-butyric (IBA) acid gel or 0.2% willow (Salix alba L.) extract gel).

Cuttings were placed in a growth chamber for twelve days then assessed on their rooting success rate and root quality using a relative root quality scale. The IBA gel delivered a 2.1 times higher rooting success rate and 1.6 times higher root quality than the willow extract. Removing leaf tips reduced rooting success rate from 71% to 53% without influencing root quality. Cuttings with three leaves had 15% higher root quality compared to those with two, but leaf number did not influence rooting success rate. Position of cutting had little effect on rooting success or quality. To achieve maximum rooting success and root quality, cuttings from either apical or basal positions should have at least three fully expanded, uncut leaves and the tested IBA rooting hormone is preferential to the willow-based product.
Please post the abstract of any studies and don't expect others to click links to outside sources if you want to actually have a conversation about something.



dank.Frank
 

Douglas.Curtis

Autistic Diplomat in Training
I wanted to bring to your attention this interesting study on cloning... which also belies some common practices usually seen as profitable

"Vegetative propagation of cannabis by stem cuttings:
effects of leaf number, cutting position, rooting hormone
and leaf tip removal"

Canadian Journal of Plant Science


Direct pdf download:

https://tspace.library.utoronto.ca/bitstream/1807/90574/1/cjps-2018-0038.pdf
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. :D
 

Ibechillin

Masochist Educator
Full Explanation:

Plant Culture and Treatments

Cannabis [Cannabis sativa L. ‘WP:Med (Wappa)’] cuttings were taken at a length of ≈13 cm and with three fully-expanded leaves from stock plants. Cuttings were taken from the ends of axial limbs and cut at a 45˚ angle. Each cutting was rooted in a 5.7 cm wide, 5.7 cm tall peat-based pot (Jiffy Products N.B. Ltd., NB, Canada) containing Pro-Mix PG Organic growing substrate (Premier Tech ) and arranged in trays at a density of 266 plants/m2. The substrate was soaked in a solution of ‘Spurt’ liquid organic fertilizer (2.0N–0.0P–0.83K; EZ-GRO Inc.) at a rate that supplied 123 mg N·L-1.


The experiment was a full factorial completely randomized design with four factors (rooting hormone, leaf number, cutting position and leaf tip removal), two levels per factor and 10 replications per factor combination.

For leaf number, cuttings had either one fully-expanded leaf removed (two leaves remaining) or were left with three leaves.

For cutting position, cuttings from terminal shoots were taken from either an apical position (node 10 and higher) or a basal position (below node 10).

For the leaf tip removal treatment, a portion of leaf tips (≈1/3 of the leaf area) was removed from the fully expanded leaves or the leaves were left uncut.

For the rooting hormone factor, the base (≈5 cm) of each stem was dipped in either 0.2% indole-3-butyric acid gel (synthetic rooting hormone; EZ-GRO Inc.) or in a 0.2% willow extract rooting gel (organic rooting hormone; EZ-GRO Inc.).

Propagation Environment

Trays were randomly arranged in a walk-in growth chamber (Conviron ATC60; Controlled Environments Ltd., Winnipeg, MB, Canada) and cuttings were misted with reverse osmosis (RO) water once, when they were placed in the chamber. From days 0 to 4 after cuttings were placed in the substrate (DAP), RH was maintained at 95% (s.d. ±1.3), reduced to 80% (s.d ±1.3%) for 5-8 DAP and to 60% (s.d. ±1.5%) for 9-12 DAP. Temperature was maintained at 24 ˚C (s.d.±0.04˚C) (day/night) for the entire period. Fluorescent lighting (Philips Lighting, Markham, ON, Canada) was used to maintain an 18-hour photoperiod. Photosynthetically active radiation (PAR) at canopy level was maintained at 50µmol·m-2s-1 (s.d. ±0.6 µmol·m-2s-1) for 0-4 DAP 1-5, 80µmol·m-2s-1 (s.d. ±0.7 µmol·m-2s-1) for 6-8 DAP and 115µmol·m-2s-1 (s.d. ±0.5 µmol·m-2s-1) for 10-12 DAP.

Rooting Assessment and Harvest

The bottom of the trays was observed daily from 7 DAP onwards for protruding roots, and cuttings were harvested at 12 DAP when approximately more than 50% of the cuttings showed visible roots at the bottom of the tray. Rooting success rate was measured on a binomial scale in which any visible adventitious root formation was considered rooted. Rooting success was calculated as the percentage of cuttings with roots in each treatment. Successfully rooted cuttings were assigned to either of two classifications based on degree of adventitious rooting: A root quality index (RQI) score of ‘1’ or ‘2’ was assigned by a third party without knowledge of the applied treatments based on a visual reference (Fig 1). Before RQI measurements, the substrate was washed from rooted cuttings with RO water and ratings were determined by a third party without knowledge of the applied treatments.

RESULTS

Rooting hormone had the greatest effect on both rooting success rate and root quality. The synthetic hormone delivered a 2.1 times higher rooting success rate (84% vs. 40%;χ2 = 39.0,P <0.0001) and 1.6 times higher root quality (1.6 vs. 1.0;χ2 = 41.1,P < 0.0001) than the organic hormone.[/B]

Removing leaf tips had the second greatest effect on rooting success rate. When leaf tips were removed, rooting success rate was lowered from 71% to 53% (χ2 = 9.8,P = 0.0018), though there was no effect on root quality.

Leaf number had no effect on rooting success rate, but rooted cuttings with three leaves had 15% higher root quality than those with two (1.5 vs.1.3;χ2 = 4.3,P = 0.038).

Cutting position did not influence rooting success rate or root quality. There was however, an interactive effect between cutting position and leaf tip removal on rooting success rate (Fig. 4). When leaf tips were removed, cuttings of basal origin had lower rooting success rate than apical cuttings (43% vs. 63%;χ2 = 5.7,P = 0.0169).

Rooting success was similar between cuttings with two and three leaves, suggesting that two leaves may provide sufficient carbohydrates, auxin and rooting co-factors (Haissig 1974) for successful rooting in cannabis. In the propagation of stem cuttings, increased photosynthetic surface area and resultant carbohydrate supply generally increased rooting success rate until another factor such as evapotranspiration stress became limiting (Davis and Potter 1989). Cuttings with three leaves showed no signs of wilting or other indications of evapotranspiration stress. It is likely that both two- and three-leaf treatments exhibited little evapotranspiration induced water stress in the stable, high humidity provided in this trial. It is estimated that under conditions of lower or less stable humidity, fewer leaves would deliver improved rooting success rate as these cutting would have a lower demand for humidity. Notably, three leaves increased root quality over two. The observed quality improvement was likely caused by the additional carbohydrates, rooting co-factors, endogenous auxin (Haissig 1974) or a combination of these factors provided by the additional foliage.

Further study is required to evaluate the effect of each of these factors and their interactions on cannabis stem cuttings to discern their relative importance.

Based on this finding, it is recommended that cannabis cuttings be taken with three or potentially more leaves (to improve rooting quality) so long as humidity during propagation can be adequately maintained.

It was expected that cutting leaf tips would have a similar effect to reducing leaf number since the source and thus potentially the amount of photosynthetic material was manipulated; however, cutting leaf tips reduced rooting success and had no effect on rooting quality.

Both cutting leaf tips and leaf number alter surface area for evapotranspiration and photosynthesis; however, there was a notable difference in the effects of these treatments. Leaf cutting influenced rooting success rate while leaf number influenced root quality. Further study is necessary to discern the reason for these differing effects. Based on these findings, it is recommended that leaf tips not be cut in cannabis cuttings; and, if less leaf material is desired to conserve space in the propagation environment or to prevent evapotranspiration stress, then fewer whole leaves be used instead.


Cutting Position

There was no indication that basal cuttings had improved rooting success rate or quality over apical cuttings
. Similar results were found in stem cuttings of fever tea (Soundy et al. 2008) and may be attributed to the lack of distinct stages of maturation in these herbaceous plants in contrast to most hardwood species (Schreiber and Kawase 1975; Morgan and McWilliams 1976; Husen and Pal 2006). These findings suggested that in cannabis, cutting position does not play an important role in rooting.

There was an interactive effect between leaf tip removal and cutting position. Cuttings from basal positions with two leaves had lower rooting success rate than any other combination of these two factors. In general, basal cuttings had smaller leaves (general observation without measurement) than apical cuttings which, through cutting of leaf tips, were left with less overall leaf surface area. The reduction in photosynthesis resulting from the smaller
leaf area might have then resulted in the lower rooting success rate.
 
Last edited:

CannaRed

Cannabinerd
Great study! I noticed that it says 2-3 FULLY expanded leaves. Most of time thenlowr branches leaves aren't as big. Is that what they mean? Use cuts from branches with full grown leaves?
Won't be cutting tips.
 

Ibechillin

Masochist Educator
In a general sense the results say the more total initial leaf surface area a cutting has the better as long as the environment can be maintained.
 

Sign

Member
Good stuff. I clipped my leaves because the interwebs said so, I'll try leaving them alone next time.
 

CannaRed

Cannabinerd
Good stuff. I clipped my leaves because the interwebs said so, I'll try leaving them alone next time.

One thing I have learned from grow books, sites, forums is that somewhere there is someone doing the exact opposite of what you learned. And they might be killing it.
 

Somatek

Active member
One thing I have learned from grow books, sites, forums is that somewhere there is someone doing the exact opposite of what you learned. And they might be killing it.

Until now we didn't have reliable plant specific studies to draw from, now that the UoG is building a lab specifically to study the science of cannabis cultivation we'll finally have quantifiable data to work from. That's a fundamental shift and personally I'm happy to adapt my methods when I find out there's a better way, like not clipping leaf tips.
 

Defacto

Member
I wanted to bring to your attention this interesting study on cloning... which also belies some common practices usually seen as profitable.....


Thank you for showing this to us ramse!

It discredits several of my cloning practices.
 

insomniac_AU

Active member
Thanks for posting, sort of what I thought anyway.


Good stuff. I clipped my leaves because the interwebs said so, I'll try leaving them alone next time.

I tried it too because I believed the interwebz urban myth. I haven't clipped leaves for years and I rarely have a cutting not root. It really isn't difficult. Temperature and humidity are the biggest factors especially in the first few days. It's really the same with cracking seeds TBH. For example if it's too cold you're going to have issues.
 

ramse

Active member
the study on cloning is part of a monograph entitled:
Propagation and Root Zone Management for Controlled Environment Cannabis Production
Author: Caplan, Deron M.

https://atrium.lib.uoguelph.ca/xmlui/handle/10214/14249

ABSTRACT

Cannabis producers lack reliable information on the horticultural management of their crops. This thesis research was designed to improve horticultural practices for controlled environment cannabis production; topics included propagation, growing substrates, fertilization, and irrigation. To optimize the procedures for taking vegetative stem cuttings in cannabis, several factors were evaluated on how they affect rooting success and quality (Chapter Two). These included number of leaves, leaf tip removal, basal/apical position of cutting on the stock plant, and type of rooting hormone. Removing leaf tips reduced rooting success and cuttings with three fully-expanded leaves had higher rooting success and quality than those with two. Also, a 0.2% indole-3-butyric gel was more effective than a 0.2% willow extract gel to stimulate rooting and cutting position had no effect on rooting. Coir-based substrates with different physical properties were evaluated during the vegetative and flowering stage of cannabis production; optimal organic fertilizer rates were established for each substrate (Chapters Three and Four). During the vegetative stage, cannabis performed well in both tested substrates despite the ≈11% difference in container capacity (CC) between them. During the flowering stage, the substrate with lower CC increased floral dry weight (yield) and the concentration and/or yield of some cannabinoids, including THC, compared to the substrate with higher CC. The optimal organic fertilizer rate varied by substrate during the flowering stage but not during the vegetative stage; higher fertilizer rate during the flowering stage increased growth and yield but diluted some cannabinoids. Finally, the effects of controlled drought stress timing and frequency during the flowering stage were explored on floral dry weight and secondary metabolism (Chapters Five and Six). When drought was applied during week seven of the flowering stage, through gradual substrate drying over eleven days, floral concentration and content per unit growing area of major cannabinoids were increased. When drought was applied over a period of ≈8 days during week seven, cannabinoid content was similar to a well-watered control; though, dependent on drought timing, the content of some terpenoids varied. This research provided evidence-based information that can help growers improve the quality and yield of their cannabis crops.

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