Advanced Marijuana Cultivation
Dark period before harvest in the
The Grow Room forums; what of the revers
can i leaves the lights on for a week then harvest sences i will be drying ...
what of the revers
can i leaves the lights on for a week then harvest sences i will be drying in darkness anyways for 5-7 days
leave the lights on for the last 5-7 days then harvest what of this
"We do not have time for this kind of silliness. We’re not going to be able to solve our problems if we get distracted by sideshows and carnival barkers.” - President Obama
Rick, I agree with what you are proposing, just not on such a drastic time scale. Yes, when you reach harvest growth has ceased and so has thc production, but you are proposing turning the lights off a week before if I'm not confused. I believe there are exceptions to a lot of your points too though. The first thing you said would be obviously as counterproductive as what I am supposing your idea over such an extended time period to be. The plant would not be able to use the ATP and NADH it has worked hard at producing during the day. Now, for your lettered points:
Originally Posted by RickWhite
A. I agree completely!
B. If environment wasn't that significant, then we wouldn't be debating over how to alter it to increase thc right now.
C. I believe this is true to an extent. I think the inverse is more true, shorter light periods induce budding and thc production, which in turn, means longer dark periods, but not to the extent that where there is not enough light to complete one circadian rythm.
D. I agree!
I also believe what you are suggesting about the chlorophyll would be a wonderful idea. The drying and curing process could possibly be much quicker. I am just not sure on the time scale of your proposal though, convince me otherwise.
Well said, but remember what we are suggesting here is to take away one of neccessary elements to complete the calvin cycle.
Originally Posted by mhg26
A man should look for what is, and not for what he thinks should be.
Here's where I think you are thinking about this incorrectly. If the time to harvest is x weeks, then shutting the lights down two weeks early will decrease the time to harvest by two weeks. IOW, the time specified is based on when the plant is mature in bud and weight density otherwise they would judge the strain to have finished earlier. So ending your light cycles too early will stop the photosynthesis cycle and carbohydrate and THC production will grind to a halt.
Taken from marijuana Botany by Robert Clarke
Factors Influencing THC Production
Many factors influence the production of THC. In general, the older a plant, the greater its potential to produce THC. This is true, however, only if the plant remains healthy and vigorous, THC production requires the proper quantity and quality of light. It seems that none of the biosynthetic processes operate efficiently when low light conditions prevent proper photosynthesis. Research has shown (Valle et al. 197 that twice as much THC is produced under a 12-hour photoperiod than under a 10-hour photoperiod. Warm temperatures are known to promote metabolic activity and the production of THC. Heat also promotes resin secretion, possibly in response to the threat of floral desiccation by the hot sun, Resin collects in the heads of glandular trichomes and does not directly seal the pores of the calyx to prevent desiccation. Resin heads may serve to break up the rays of the sun so that fewer of them strike the leaf surface and raise the temperature. However, light and heat also destroy THC. In a drug strain, a bio-synthetic rate must be maintained such that substantially more THC is produced than is broken down. Humidity is an interesting parameter of THC production and one of the least understood. Most high-quality drug Cannabis grows in areas that are dry much of the time at least during the maturation period. It follows that increased resin produc. tion in response to arid conditions might account for increased THC production. High-THC strains, however, also grow in very humid conditions (greenhouses and equatorial zones) and produce copious quantities of resin. Cannabis seems not to produce more resins in response to dry soil, as it does to a dry atmosphere. Drying out plants by with-holding water for the last weeks of flowering does not stimulate THC production, although an arid atmosphere may do so. A Cannabis plant in flower requires water, so that nutrients are available. for operating the various bio-synthetic pathways.
There is really no confirmed method of forcing increased THC production. Many techniques have developed through misinterpretations of ancient tradition. In Colombia, farmers girdle the stalk of the main stem, which cuts off the flow of water and nutrients between the roots and the shoots. This technique may not raise the final THC level, but it does cause rapid maturation and yellow gold coloration in the floral cluster (Partridge 1973). Impaling with nails, pine splinters, balls of opium, and stones are clandestine folk methods of promoting flowering, taste and THC production. However none of these have any valid documentation from the original culture or scientific basis. Symbiotic relationships between herbs in companion plantings are known to influence the production of essential oils. Experiments might be carried out with different herbs, such as stinging nettles, as companion plants for Cannabis, in an effort to stimulate resin production. In the future, agricultural techniques may be discovered which specifically promote THC biosynthesis.
In general, it is considered most important that the plant be healthy for it to produce high THC levels. The genotype of the plant, a result of seed selection, is the primary factor which determines the THC levels. After that, the provision of adequate organic nutrients, water, sunlight, fresh air, growing space, and time for maturation seems to be the key to producing high-THC Cannabis in all circumstances. Stress resulting from inadequacies in the environment limits the true expression of phenotype and cannabinoid potential. Cannabis finds a normal adaptive defense in the production of THC laden resins, and it seems logical that a healthy plant is best able to raise this defense. Forcing plants to produce is a perverse ideal and alien to the principles of organic agriculture. Plants are not machines that can be worked faster and harder to produce more. The life processes of the plant rely on delicate natural balances aimed at the ultimate survival of the plant until it reproduces. The most a Cannabis cultivator or researcher can expect to do is provide all the requisites for healthy growth and guide the plant until it matures.
Flowering in Cannabis may be forced or accelerated by many different techniques. This does not mean that THC production is forced, only that the time before and during flowering is shortened and flowers are produced rapidly. Most techniques involve the deprivation of light during the long days of summer to promote early floral induction and sexual differentiation. This is sometimes done by moving the plants inside a completely dark structure for 12 hours of each 24-hour day until the floral clusters are mature. This stimulates an autumn light cycle and promotes flowering at any time of the year. In the field, covers may be made to block out the sun for a few hours at sunrise or sunset, and these are used to cover small plants. Photoperiod alteration is most easily accomplished in a greenhouse, where blackout curtains are easily rolled over the plants. Drug Cannabis production requires 11-12 hours of continuous darkness to induce flowering and at least 10 hours of light for adequate THC production (Valle et al. 197. In a greenhouse, supplemental lighting need be used only to extend daylength, while the sun supplies the energy needed for growth and THC biosynthesis. It is not known why at least 10 hours (and preferably 12 or 13 hours) of light are needed for high THC production. This is not dependent on accumulated solar energy since light responses can be activated and THC production increased with only a 40-watt bulb. A reasonable theory is that a light-sensitive pigment in the plant (possibly phytochrome) acts as a switch, causing the plant to follow the flowering cycle. THC production is probably associated with the induction of flowering resulting from the photoperiod change.
Cool night temperatures seem to promote flowering in plants that have previously differentiated sexually. Extended cold periods, however, cause metabolic processes to slow and maturation to cease. Most temperate Cannabis strains are sensitive to many of the signs of an approaching fall season and respond by beginning to flower. In contrast, strains from tropical areas, such as Thailand, often seem unresponsive to any signs of fall and never speed up development.
Peer review studies have shown elevated levels of THC after exposure to UV. I agree with you that UV should be damaging and breaking down THC, but I suggest that maybe the THC production out paces the breakdown. Remember, it can take years to degrade THC with light but the plant produces a majority of it in 8-14 weeks. Also, some compounds, sunscreen comes to mind, scatter UV light, others absorb it and re-radiate it as heat. Keep in mind the many cannabinoids beside THC, they could all be working in conjunction as the plant's natural sunscreen, some absorbing, some scatter, etc.
Here's the abstract of at least one study showing an increase in THC after exposure to UV.
UV-B RADIATION EFFECTS ON PHOTOSYNTHESIS, GROWTH and CANNABINOID PRODUCTION OF TWO Cannabis sativa CHEMOTYPES
John Lydon* 2 Alan H. Teramura 1 C. Benjamin Coffman 3 1 Department of Botany, University of Maryland, College Park, MD 20742, USA 2 USDA-ARS, Southern Weed Science Laboratory, P.O. Box 350, Stoneville, MS 38776, USA 3 USDA-ARS, Weed Science Laboratory, AEQ. I, Beltsville, MD 20705, USA
*To whom correspondence should be adressed.
Copyright 1987 American Society for Photobiology
The effects of UV-B radiation on photosynthesis, growth and cannabinoid production of two greenhouse-grown C. sativa chemotypes (drug and fiber) were assessed. Terminal meristems of vegetative and reproductive tissues were irradiated for 40 days at a daily dose of 0, 6.7 or 13.4 kJ m-2 biologically effective UV-B radiation. Infrared gas analysis was used to measure the physiological response of mature leaves, whereas gas-liquid chromatography was used to determine the concentration of cannabinoids in leaf and floral tissue.
There were no significant physiological or morphological differences among UV-B treatments in either drug- or fiber-type plants. The concentration of Δ9-tetrahydrocannabinol (Δ9-THC), but not of other cannabinoids, in both leaf and floral tissues increased with UV-B dose in drug-type plants. None of the cannabinoids in fiber-type plants were affected by UV-B radiation.
The increased levels of Δ9-THC in leaves after irradiation may account for the physiological and morphological tolerance to UV-B radiation in the drug-type plants. However, fiber plants showed no comparable change in the level of cannabidiol (a cannabinoid with UV-B absorptive characteristics similar to Δ9 THC). Thus the contribution of cannabinoids as selective UV-B filters in C. sativa is equivocal.
(Received 29 August 1986; accepted 24 February 1987)
Mindphuk, I am too tired to read your entire post, but I am completely with you on the influence uvb has on thc production. The most potent outdoor weed in the world comes from areas that have high uvb concentrations. The science behind this is not completely understood, but marijuana man does a great job explaining what is known in this youtube video. I am so convinced, I am going to buy a uvb light from a reptile store. Everyone watch this!
I am sorry to diverge from your hypothesis Rick, but I think this information in this video can be beneficial to us all.
A man should look for what is, and not for what he thinks should be.
Learning How To Roll
Learning How To Roll
lights off...this needs good timing..and differs in every strain..specially sativas...so observe your girls carefully... =)
so ive been doin 11light ... 13 dark since my 3rd week of flower .... to lower heat and electric bill....
mostly cause after 10 hrs of my 400 being on ..... it gets hot ....like about 86-90 degrees...
i think that his debate helped us shed light on this mystery ....however
i believe ... without fact or resource..... just using my convientional wisdom......
that the more light a plant get the more energy is produced .....
but does the plant really need 12 hrs.....
and is 10hrs gonna really stop production.....
i dont think thats the case....
yeah it might not producce as much energy....
but less hrs of light tellls the plant fallscoming time for budding....
furthermore in nature in the fall light cycles can go from aprox(depending where u live)
from 14hrs of light in summer ....to 10hrs in the fall to winter periods.....
that seeems natural ... in nature it not 12/12 the whole flowering time.....
Moving along ... ive seeen many outdoor grows that only get about 8 to 10 hrs of direct sun.....
and the plants still grow nicely....
so should i be worred that because my plants only get 11hrs of light thatll theyll stop producing as much as they should?????
First, I would like to see the actual studies, how they were conducted and what the actual data was.
Second, I'm not suggesting turning off the lights before the buds are fully mature. I am suggesting allowing the buds to fully mature and then shutting them off for several days. I highly doubt runing a 10 hour light cycle as opposed to a 12 hour life cycle makes much difference in THC production.
One thing you always need to be careful of is citing a single study. In university science department there is a concept known as "publish or perish." This essentially means that if an aspiring professor wants his career to survive he had better come up with something to publish. Again, I would like to see for myself how those studies were conducted and what the actual data is. A lot of times a researcher will publish something calling it an "increase" but when reviewed it shows that the "increase was within the margin of error of the study.
What I observed (granted just with a 30x microscope) was a marked increase in the milky color of trichomes. The milky color is no doubt caused by the presence of something scattering light. Whether or not it's THC I don't know.
But, you could also do both. You could use additional UVB exposure up until harvest time and then flush the plants in the darkness. It seems unlikely to me that the plant will slam on the breaks with regard to THC production the moment the lights go out. That's kind of like saying the minute you stop eating your body begins muscle wasting. The plant will still have ATP stores that contain a significant amount of energy - I'd be willing to bet THC production is still possible.
But again, if light is so crucial to THC production wouldn't it be better to leave the lights on 24 hours a week before harvest?
Then I didn't understand. If you wait until harvest to shut off the lights then flush, how is that going to be better than just harvesting and drying? They don't get light while drying or curing so it will be essentially the same except if you keep them alive for 2 more weeks, that extends the time until it is ready to smoke and I doubt it will do anything more than if you properly flushed before hand.
Originally Posted by RickWhite
Please don't try to claim that a paper is invalid just because researchers have to publish. The very fact that it passed peer review is enough to take it seriously. Sure, results need to be confirmed but this study was 1987, and I don't have access to the most current botany journals, but I would bet money that this study has already been replicated. The fact that this was an actual scientific study in a refereed journal makes it more compelling than some guy on a weed forum with a hypothesis and who's attempting to compare THC levels by trich color and smokability alone without performing an actual assay. Sorry but it is pretty damn arrogant of you to criticize a study by Dr. John Lydon, a preeminent plant physiologist at the same time you want us to take you seriously yet you don't have any substantial evidence to back up your claims.
If you want to see the full study, order a reprint or call Dr. Lydon and ask him to send you one. While you are at it, you can ask him for any additional studies he can find on the subject. I bet he'd be more than happy to comply.
By silvernomad in forum Newbie Central
Last Post: 07-09-2013, 06:24 PM
By splifman in forum Harvesting And Curing
Last Post: 03-17-2010, 05:12 PM
By geekin69 in forum General Marijuana Growing
Last Post: 06-24-2009, 07:23 PM
By shallrelicme in forum Newbie Central
Last Post: 06-19-2009, 02:53 AM
By Mr. in forum Indoor Growing
Last Post: 03-17-2009, 01:27 AM
Tags for this Thread