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High night time temperatures.

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sarah louise View Drop Down
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Topic: High night time temperatures.
    Posted: 10 September 2012 at 14:24
Just wondering if cannabis has a problem with "lights out" temperatures exceeding "lights on" temperatures?

For argument's sake 20C during lights on and 27C during lights off.


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  Quote organicgrow Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2012 at 16:53
Hey, this is taken from an article on fine tuning temperature in Cannabis Culture magazine:

"For extreme height control you may even use warmer night temperature than day, but be very careful when running settings like this, as even a zero difference between night and day temperatures will lead to leaf chlorosis (yellowing) after 2-3 weeks."

I remember Cervantes also mentioned this I can try to find it if you want.
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  Quote PetrolSS Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2012 at 17:12
actually that's identical to what i was going to mention. although i'll amend the limitations and submit that chlorosis in my experience tends to set in as soon as 10 days - by 3 weeks i'd imagine some real damage.

i'm extremely interested in your results so keep us updated word? - i still haven't decided where i'm going to set my night temperature for this next cycle. i can choose anywhere from 55-75F with only a variation of +/-1.5.
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  Quote Ganja Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2012 at 17:31
OG and PSS, that's a new one to me. Does Cervantes give a reason that the same temp for night and day can lead to chlorosis?
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  Quote PetrolSS Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2012 at 17:38
i don't recall cervantes mentioning it - but who knows my memories fucked - whatever it was i read that made me try it stressed that a temperature variation was necessary for normal, healthy growth but gave no biological reasoning for it

in my experience i've noticed chlorosis both when there was zero change of temperature between night day, as well as when there was extreme, 25-40 degree temperature fluctuation between day and night
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  Quote organicgrow Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2012 at 19:35
Originally posted by Ganja

OG and PSS, that's a new one to me. Does Cervantes give a reason that the same temp for night and day can lead to chlorosis?


Hi G

I have not found the exact quote from Cervantes yet, I will keep looking.

Anyway, I looked at other literature on the subject and found some noteworthy info:

Studies have shown that the day-night temperature differential (DIF) variable can negatively or positively affect growth. When day temperature is moderately higher than night temperature (+DIF), cell expansion as well as chlorophyll production is accelerated.

A highly negative temperature differential (-7DIF or more) decreases cell expansion therefore stem elongation is controlled making it useful as a temporary height control tool in cannabis culture but because exposure to extremely (-DIF) conditions contributes to a general reduction in chlorophyll production, chlorosis can occur over time.

I can cite my references if you are interested in a more in-depth read.
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  Quote obsessive Quote  Post ReplyReply Direct Link To This Post Posted: 10 September 2012 at 22:32
makes sense that the babies get fucked up with that sort of confusion. In real life the plants have evolved to appreciate warm sunny days and cooler dark nights. Best not try and fight mother nature
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Posted: 11 September 2012 at 02:09
Cites please OG. I haven't found anything specific to cannabis, only a couple of studies on chrysanthemum and sweet basil.

This isn't a problem for me, my grow inside the house so the plants are more protected from the changes in weather, but I know a couple of people growing in garden sheds and it is for them that I ask the question.

It's not a matter of 'fighting mother nature' Obsessive, more a case of working with the ambient conditions as best we can. During winter, lights on at night and off during the day keeps the plant's temperature pretty close to the ideal range, but as the season changes we have higher temperatures during the day (when the lights are off) and still quite cold temperatures during the night (when the lights are on) and that what leads to the negative temperature differential (or -DIFF).
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  Quote PetrolSS Quote  Post ReplyReply Direct Link To This Post Posted: 11 September 2012 at 03:00
word, i know several growers who have the same problem with indoor gardens when the house isn't so well insulated. I should rephrase that though - while they have problems with the changing of the seasons for temperature regulation - they've never had (not one of them) any issue negatively affecting plant growth because of those seasonal fluctuations, however.

I would imagine that the chlorosis issue is a moot point in this context as even if you have one or two days with a negative differential, the very point that the season is changing suggests that no two days will have the same differential. lessening the possibility for chlorosis from consistent negative differential
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  Quote organicgrow Quote  Post ReplyReply Direct Link To This Post Posted: 11 September 2012 at 19:38
I checked the Cervantes book as best as I could and I was not able to find the quote. Either it eluded me this time or my brain is confusing memory data. The latter being the more probable %3c3cig%3c3c

The only mention of DIF in cannabis literature that I could find was the quote from the magazine. It seems that (-DIF) is mostly considered an artificially and temporarily created condition for height control during specific times in plant growth and therefore, there was not much to be found on the subject of unintentional and prolonged exposure to the condition.

However, according to these sources, some of which are plant specific and some of which are on general plant physiology, it can be surmised that the (-DIF) condition generally impedes growth and the claim of chlorosis after prolonged exposure in cannabis is plausible due to the reduced Chlorophyll synthesis reported by these texts. I believe the severity of the problem however can not be determined without plant-specific data.


http://www.crophouse.co.nz/files/Gr_P02_-_Using%20temperature%20for%20plant_control_-_view.pdf

http://journal.ashspublications.org/content/131/3/309.full.pdf

http://www.griffins.com/tech_service/newPdfs/Controlling%20Plant%20Stretch%20Through%20the%20Morning%20Temperature%20Dip.pdf

http://plantsinaction.science.uq.edu.au/edition1/?q=content/14-3-1-daynight-temperature-differential
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  Quote sarah louise Quote  Post ReplyReply Direct Link To This Post Posted: 11 September 2012 at 23:13
Thanks OG :)
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