High temps during veg?

[sahima]

Hot summer here i live. Usually i am starting my indoor grow season during middle Semptember with fluros, ending the grow near christmas with perfect low temps in the growroom.
This time i would like a long sativa scrog grow(8 +weeks veg) and i was thinking to start at august. Temps with fluros in the growroom are near 30-32C degrees(thermometer placed straight under the fluro), and my estimation is that if ,after the first 2-3 weeks of growth, when i will have to place an hid for optimum lighting, temps will climp as high as 35C (with ventilation).
What do you think should i give it a try? I have a feeling that the plants can do ok with a max 35C during veg, hope i am right...

 

[BagseedSamurai]

Dude, 95 degrees will make your grow a veritable wasteland. That kind of tempts will stunt or stop growth altogether and should really be avoided. You can try, but keep the temps lower than that!

 

[ibjamming]

I've had them at an indicated 112F...canoe leaves...but they did fine. Keep them watered, VERY good ventilation, they'll make it.

Does anyone have a max temp for Cannabis? There must be an extreme maximum.

 

[sahima]

First grow of mine, i placed a 400Hps into the closet, closed the doors and planted the seeds straight to soil with 40-45C and near 80-90%RH. The fastest germination i ever had, 2-3 days all the three seeds had the first true leaves, no shit! And for the first days had some very fast and vigorous growth, never seen this again. Soon after probs started even with lower temps and end up with shitty premature weed. Thanks for your input...

 

[Iron_Lion]

If you stress them out in veg you could end up with more males or herms.

 

[BagseedSamurai]

If you stress them out in veg you could end up with more males or herms.

Although I understand the theory behind it, I am of the mindset that once sex is determined, it stays that way. And during reproduction is when sex is determined. So I think with seeds your environment won't matter for sex unless they CHANGE sex.
My .02

 

[sahima]

For sure i will keep them with a shorter photoperiod like 18/6, and only blue-white spectrum lamps, and maybe higher humidity like 70% will be better(?) . Hope sativas will be strong enought to take the heat with minimum stress. After their first weeks temps will start to drop . We will see...Greetings

 

[Mr. Greengenes]

I've seen temps over 105F quite a few times indoors without a problem. Matter of fact, plants grow fast in the high heat. But that is with containers, which are essentially air cooled. I doubt you could do that with a water culture system. Also, direct fans are always a bad idea, but even worse in the heat because they force extra transpiration.

 

[ibjamming]

Although I understand the theory behind it, I am of the mindset that once sex is determined, it stays that way. And during reproduction is when sex is determined. So I think with seeds your environment won't matter for sex unless they CHANGE sex.
My .02

Sex IS determined...however expression is another thing. The environment can change that.

 

[BagseedSamurai]

Sex IS determined...however expression is another thing. The environment can change that.

Agreed. Changing the sex doesn't change the DNA determinates, though. So if you stress a plant and it gets pollen sacs, but has female dna.. it is still female.

Anyway, semantics.

I was wondering, as I am having the same problem as the OP. I just hooked up the tent. Ambient room temp stays at about 80. The tent seems to be staying a fairly constant 90. When the season changes it will be less difficult to deal with. I have the tent setup to where the fan pulls air through the air-cooled light holes at each side from the other side of the tent. A box fan inside to help circulate the air. I am guessing 10 degrees is about the increase I will see with this project.

So.. does anyone have that max for cannabis temps? 90 does seem a bit high but I have seen cannabis do "okay" in higher temps.

Edit: The reason why plants seem to to better in higher temps is due to the fact that heat is the main catalyst for molecular reactions in cells. The higher the temps, the lower amount of energy needed for the reaction. The problem with high temps is the threat of denaturing the cell.

 

[Iron_Lion]

Although I understand the theory behind it, I am of the mindset that once sex is determined, it stays that way. And during reproduction is when sex is determined. So I think with seeds your environment won't matter for sex unless they CHANGE sex.
My .02

This is an artical published by Dutch Passion

n November 1998 we introduced our "Female Cannabis Seed". We did this after our own experiments showed that from female seed, we acquired almost 100% female off-spring.

In the meantime we are six months further on . We have received a lot of feed-back from our customers. The reactions are mostly positive, clients who have successfully produced almost 100% female off-spring. However there have been reactions from customers who found a few hermaphrodites or males plants. Apparently environmental influences affect the sex of the female seeds as well. Because of the fact that Female seeds do not grow into female plants under all circumstances, we changed the name from "Female Cannabis Seeds" into "Feminised Cannabis Seeds".

From literature and from our own findings it appears that the growth of a male or a female plant from seed, except for the predisposition in the gender chromosomes, also depends on various environmental factors. Not only the origination of entirely male or female plants is partly affected by these environmental factors, the number of male and female flowers on a hermaphrodite plant is affected as well. The environmental factors that influence the sex of the plant (or the flower in the case of hermaphrodites), are among other things:

The quantity of nitrogen and potassium of the seedbed.
Humidity and moistness of the seedbed.
Level of temperatures.
Colour of the light used.
Length of daylight.
Stress, any form of stress, makes that more male individuals will originate from seed. Even the taking of cuttings from female plants may produce male or hermaphrodite cuttings.
To optimise the result, changes in one or more of the above-mentioned environmental factors for a certain period during growth, may be applied. During this time these environmental factors will deviate from the standard growing system for maximum harvest and quality, as described in nursery literature. The desired change(s) in the environmental factor(s) are started from the moment that the seedling has three pairs of real leaves (not counting the seed-lobes). This is the moment that male and/or female predisposition in florescence is being formed. After approximately two weeks the standard growing system can be reconverted to.
Of the 5 above-mentioned environmental factors the first three are the most practical:

1. Level of nitrogen and potassium of the seedbed: A heightening of the standard level of nitrogen makes for more female plants originating from the seeds. A lowering of the nitrogen level shows more male plants. A heightening of the level of potassium tends to show more male plants, while a lowering of the potassium level shows more female plants. A combination of a higher nitrogen level for the period of a week or two and a lowering of the potassium level is recommended.
2. Humidity and moistness of the seedbed: a higher humidity makes for an increase in the number of female plants from seed, a lowering for an increase in male plants. The same is valid for the moistness of the seedbed.
3. Level of temperatures: lower temperatures make for a larger number of female plants, higher temperatures for more male plants.
4. Colour of light: more blue light makes for female plants from seed, more red light makes for more male plants.
5. Hours of daylight: few hours of daylight (e.g. 14 hours) makes for more female individuals, a long day (e.g. 18 hours) makes for more male plants. *


Now let me just make a few adjustments here to this. You can do whatever you want to your plants in seedling stage and early vegetative stage of growth and it will not effect your final male to female ratios. The time when things should be near perfect is in or around the 3rd to 4th week of vegetative growth. This is the CRITICAL TIME for getting those female ratios up and up. I realized this clearly when noticing how some plants hermed because of problems that occurred around this period of the plants development. If the problems occurred before this time - no herms. So for this reason I surmised that this is when the crucial gender selection is made by the plant. Now I believe that the genders are set in the seed however the environment has a massive impact on how this is expressed in the final phenotypic expression of the plants gender. There are probably many genes that govern this, however lets get into how to up these female ratios.

At the 3rd to 4th week of vegetative growth make sure that your plants are free from stress. No pests attacks, no fungi attacks, no mold, no irregular photoperiod, not underwatered, not overwatered, not pruned or topped, a cannabis friendly soil mix, not recently transplanted, no small pots. If have these basic growing conditions under control then we can move onto the real forces of female production from standard seeds.

N:K and nutrients. What this simply boils down to is that you have the right nutrients present in the right ratios. A nutrient formulation that has roughly equal parts N, P and K is great but if the P levels go up or the N levels go down you are starting to look at a flowering type food for cannabis. If you do this then your odds of producing mostly females is greatly decreased. Make sure that you get those N, P and K levels to almost run from higher to lower amounts from N to P and K. I have noticed that equal portions of N to P an K can help with the female ratios but the higher N is certainly more helpful. So around the 3rd of 4th week of growth make sure that the ratios are good and that P or K has not gone above the N and P or else more males will occur. Obviously this means to avoid overfeeding your plants around this time too.

Never let your medium dry out completely around the 3rd to 4th week of vegetative growth. If you make sure to water occasionally, but not to overwater your plants, you will get those female ratios on the up and up. Overwatering or drying out of the medium will only produce more males. For consistent results in getting more females keeps those mediums moist.

Humidity. Now this is the tricky one. High humidity levels only promote fungi and mold development and lowering humidity levels is the way to cure most of this rot but by keeping those humidity levels up in or around the 70 rH factor will help to produce more females. If you have a low humidity grow room then you should get to hold of a humidifier. Now high humidity levels like 70rH cause the medium to dry out a lot quicker so you got to keep this under control too. Keep those mediums moist and those rH levesl at 70. This will help to improve those female to male ratios. Again, getting them on the up and up.

If you run the 24/0 photoperiod then do not allow those temps to go anywhere above 85 unless you have an equatorial strain. 75 is the best but going a little lower is not a problem for helping those female ratios. If you can get in at around 65 then those females are going to be popping up all over the place. The problem with this is that some growers like to use the 18/6 photoperiod and when the lights are off the temps drop from around 65 to 50 and even less. Try not to be below 55 because this has the adverse effect on the plants producing more males than females. Again between 65 and 75 is where you want to be during the 3rd to 4th week of vegetative growth, the preference being 70.

Invest in a MH Light for vegetative growth. Dump the HPS bulb for flowering later. I have noticed that HPS lighting during vegetative growth simply sends those males to female ratios all over the place. With MH lamps the females are everywhere. Invest in some MH HID lights. It makes all the difference in getting those females to show more often. This is worth repeating! MH Bulbs produce more females under optimal conditions especially if they are present during the 3rd and 4th week of vegetative growth. Surprising enough you can start seedlings under HPS and it will not have an effect on those female ratios. Again the 3rd to 4th week of vegetative growth is what is important here.

No stress during the 3rd to 4th week of vegetative growth. That is all there is to it. If you got your garden growing in optimal conditions without plant stress then the impressive 90% to 95% females start to emerge from standard seed packs. I find that topping is best done at the second to third week of vegetative growth but that this is a little stressful and can lead to those female ratios dropping again. Avoid topping or pruning if you are looking to up the female count.

That is all I have to say for the moment. These little snippets of information in conjunction with what DP uncovered have helped my female ratios considerably. Hopefully you can see the same

 

[OMountainMix]

Soil is more forgiving of high temps than hydro is, but really, high temps will make it hard for your plants to absorb nutrients and grow correctly. It's better to spend some $ for a.c. and get a better and larger crop.

 

[BagseedSamurai]

No offense, Iron Lion (and thanks for the excerpt) but I will not believe that until I see actual data from such procedures and experiments. A normative environment does not possess the capability to change sex chromosomes. If it did, humans wouldn't be sexed until they reached sexual maturity.

Mountain: I've already exceeded my budget building my current setup. I have got to make due with what I have. I am tweaking things but it is all dependant on ambient (outside) temps for now.

 

[Iron_Lion]

No offense, Iron Lion (and thanks for the excerpt) but I will not believe that until I see actual data from such procedures and experiments. A normative environment does not possess the capability to change sex chromosomes. If it did, humans wouldn't be sexed until they reached sexual maturity.

.

Get back to me when you've grown thousands of plants like DP, until then I'll take their word over yours, besides Im not sure comparing humans and plants is a viable argument.

I also read a post of the almighty rezdog today about the very same environmental issue.

 

[BagseedSamurai]

Get back to me when you've grown thousands of plants like DP, until then I'll take their word over yours, besides Im not sure comparing humans and plants is a viable argument.

Well, I'll take basic science's word over DP, any day.

I also read a post of the almighty rezdog today about the very same environmental issue.

Rezdog is not "almighty."

..as I said. When someone can come up with credible and reliable data on the subject which leans either way, I will be more apt to believe it. Just because a couple people say so does not make it true. Any number of factors could explain DP ratio. Hell, I went a long while when I was growing 100% female plants that were not fem'd seeds, nor was the environment changed in any way. It wasn't environment, it was pure luck or happenstance that I got female seeds instead of male ones.

Flip a coin. You'll know all about sex determinants.

 

[Iron_Lion]

Mechanisms of sex determination

Cannabis has been described as having one of the most complicated mechanisms of sex determination among the dioecious plants.[63] Many models have been proposed to explain sex determination in Cannabis.

Based on studies of sex reversal in hemp, it was first reported by K. Hirata in 1924 that an XY sex-determination system is present.[61] At the time, the XY system was the only known system of sex determination. The X:A system was first described in Drosophila spp in 1925.[64] Soon thereafter, Schaffner disputed Hirata's interpretation,[65] and published results from his own studies of sex reversal in hemp, concluding that an X:A system was in use and that furthermore sex was strongly influenced by environmental conditions.[62]

Since then, many different types of sex determination systems have been discovered, particularly in plants.[56] Dioecy is relatively uncommon in the plant kingdom, and a very low percentage of dioecious plant species have been determined to use the XY system. In most cases where the XY system is found it is believed to have evolved recently and independently.[66]

Since the 1920s, a number of sex determination models have been proposed for Cannabis. Ainsworth describes sex determination in the genus as using "an X/autosome dosage type".[56]
A male hemp plant.
Dense raceme of carpellate flowers typical of drug-type varieties of Cannabis.

The question of whether heteromorphic sex chromosomes are indeed present is most conveniently answered if such chromosomes were clearly visible in a karyotype. Cannabis was one of the first plant species to be karyotyped; however, this was in a period when karyotype preparation was primitive by modern standards (see History of Cytogenetics). Heteromorphic sex chromosomes were reported to occur in staminate individuals of dioecious "Kentucky" hemp, but were not found in pistillate individuals of the same variety. Dioecious "Kentucky" hemp was assumed to use an XY mechanism. Heterosomes were not observed in analyzed individuals of monoecious "Kentucky" hemp, nor in an unidentified German cultivar. These varieties were assumed to have sex chromosome composition XX.[67] According to other researchers, no modern karyotype of Cannabis had been published as of 1996.[68] Proponents of the XY system state that Y chromosome is slightly larger than the X, but difficult to differentiate cytologically.[69]

More recently, Sakamoto and various co-authors[70][71] have used RAPD to isolate several genetic marker sequences that they name Male-Associated DNA in Cannabis (MADC), and which they interpret as indirect evidence of a male chromosome. Several other research groups have reported identification of male-associated markers using RAPD and AFLP.[24][48][72] Ainsworth commented on these findings, stating,

"It is not surprising that male-associated markers are relatively abundant. In dioecious plants where sex chromosomes have not been identified, markers for maleness indicate either the presence of sex chromosomes which have not been distinguished by cytological methods or that the marker is tightly linked to a gene involved in sex determination.[56]"

Environmental sex determination is known to occur in a variety of species.[73] Many researchers have suggested that sex in Cannabis is determined or strongly influenced by environmental factors.[62] Ainsworth reviews that treatment with auxin and ethylene have feminizing effects, and that treatment with cytokinins and gibberellins have masculinizing effects.[56] It has been reported that sex can be reversed in Cannabis using chemical treatment.[74] A PCR-based method for the detection of female-associated DNA polymorphisms by genotyping has been developed.[75]
Industrial and personal uses

 

[LUDACRIS]

Sex can be reversed "SEXUAL REVERSAL".
If you need some info on this please ask and i will dig out my files on this subject.

(good luck).

LUDA.

 

[BagseedSamurai]

Alright, finally! Some data.

There are a number of things wrong with it, such as the fact that they used hormones as an inducive determining factor. Environment may have an effect on hormones, which could determine sex on an XA basis, but in what quantity does the hormone have to be present for a shift? Can environmental factors really cause such a significant hormonal shift? Also, on an XA basis, it isn't that the "A" changes, it is that it is made to be heterosomal; allowing for either sex determinant to be expressed.

I'll do some of my own research on it, maybe. Try to get actual data in the mix.

Untill then..
//derail

 

[guest456mpy]

Got to agree with Iron Lion, here.
Been growing since the late 60's.

Definitely more expression of males in stress situations, esp heat related. It's a survival strategy for them. A real bummer for me since the summer's been so bad my ambient temp tips into the 80's even with AC on! I've been vegging some DG/Rez KQR and 3/4 have expressed themselves as males in pre-flowering stage.

BTW humans do express themselves in confused and reversed sexual ways. We haven't Identified why quite yet as we're just a bit more complicated than plants.

 

[LUDACRIS]

Alright, finally! Some data.

There are a number of things wrong with it, such as the fact that they used hormones as an inducive determining factor. Environment may have an effect on hormones, which could determine sex on an XA basis, but in what quantity does the hormone have to be present for a shift? Can environmental factors really cause such a significant hormonal shift? Also, on an XA basis, it isn't that the "A" changes, it is that it is made to be heterosomal; allowing for either sex determinant to be expressed.

YES............