Why go 24 hours lights on??

[spurr]

this whole horse to water and not drinking is silly

it has been proven long ago that one simply needs to puff in the horses face for a time, that horse is going to develop cotton mouth if you keep at it, if you keep on keepin' on before you know it that horse is just going to HAVE to take a sip of the water you led him to

so yes you can indirectly force it to drink

LOL!

when all is said and done, i'd just like to state for the record that my horse is much higher than yours

I used to work on a few horse ranches, and at one point I noticed that one horse would force its mouth open when standing around. The horse would force the fence rail between its teeth because horses can't hold their mouths open by themselves for extended periods of time. I asked the rancher why the horse was going that, and she told me it was "getting high"! I said, "yea right!". She told me when a horse forces its mouth open it can inhale much more air and that in turn makes it get high, as in stoned. She told me only very few horses will do that, but those that do such a thing, do it all the time! LOL, stoners! So I started watching the horse, and yup, it did it all the time.

Now, I am not saying she was correct, and I never took the time to fact check her...but I do love the thought about a horse getting high!

 

[spurr]

@ all,

Watching plants is one way to tell when they are getting too much light at any one time, or over the whole day. If the leafs at the upper canopy angle upward, like they are praying, that usually means the plant is trying to reduce the surface area of the leafs. Plants do this as a means to reduce the photons striking the leafs, which in turn reduces the light-energy for the plant (photon absorption). Kind of like how human squint their eye in bright sun.

Plants also 'canoe' their leafs (curl inward) to reduce surface area to reduce the photons they absorb.

If plants are 'praying' at the top section of canopy, or if the leafs are canoeing, it's a good sign too much light is being provided. If both are happening at the same time then photoinhibition (reduced rate of photosynthesis, etc) is usually soon to follow...

When the plant angles leafs upward or canoes leafs it's the plants' attempt to protect itself from light saturation and photo damage.

This is what I needed, thanks.

First time 1K bulb user here.

This is my 2nd post and the reason I signed up.

Too much light was the only thing I didn't think of. I've been playing with the temperature, the humidity, the fertlizer and never even thought of that.

After reading your explanation I found that tomato growers call it physiological leaf roll and one possible explanation for it is a buildup of carbohydrates in the leaves.

You are very welcome, it's a tidbit most growers do not know, I am glad it was helpful to you

Thanks for the info from tomato growers, I didn't know they had written about it.

 

[spurr]

Thread is kinda long... not sure if this has been mentioned but,,

When you put plants under 24/7 light without big dips in nighttime temps the plants will free run. This basically means that without external input to the plants circadian clock, it will still oscillate. Plants express their genes rhythmically, but their period is not exactly 24 hours. This means that under 24/7 lighting, you are not entraining the plant, and therefore have no idea which phase of it's circadian rhythm it's on. It may be in it's subjective day or subjective night phases at any time of the day.

Now for the important part. 24/7 lighting gives a slight disadvantage to your plants when you flip the lights to 12/12. Since you may be flipping the lights off during the plants subjective day, the plant must now entrain to this new light cycle before it can begin to flower. Only once the plant is entrained will the transcriptional activator Constans(CO) line up with the correct corresponding light period, and induce flowering. Since the external coincidence model is based on the plants biological clock matching with the corresponding day length, you will delay the onset of flowering if these do not match up.


How much? Probably tops only two or three days so not a super big deal. I also quickly want to mention that when you flip the lights to 12/12 on a free running plant it will not be able to maximize growth for that day. This is especially true if you start out your flowering period with an extended dark period, which by the way is completely stupid and makes no biological sense at all!!

Plant is in subjective night-->You switch the lights off--> Unexpectedly extended night

– Starch used up before dawn or subjective day
– Starvation genes turn on

None of this information is crucial for a successful grow but I though it'd be worth mentioning...

Great points, I am always intrigued by topics of photoadaptation. Would you mind citing some references for everyone to check out? [I would also like to read your references]

 

[smokefrogg]

I used to work on a few horse ranches, and at one point I noticed that one horse would force its mouth open when standing around. The horse would force the fence rail between its teeth because horses can't hold their mouths open by themselves for extended periods of time. I asked the rancher why the horse was going that, and she told me it was "getting high"! I said, "yea right!". She told me when a horse forces its mouth open it can inhale much more air and that in turn makes it get high, as in stoned. She told me only very few horses will do that, but those that do such a thing, do it all the time! LOL, stoners! So I started watching the horse, and yup, it did it all the time.

Now, I am not saying she was correct, and I never took the time to fact check her...but I do love the thought about a horse getting high!

hey spurr! i have family that's worked on ranches too, i told one of them about it and he said he hadn't heard of anything like that, but did have this anecdote from his time on the ranch and enjoying some good smoke with one of the horses:

Now, regarding the horses...Nope, never heard that one. Course on the same note, I used to stand at the corral fence and with my fav appy stud, I'd blow smoke up his nose. Trippy sorta horse..first couple times, he balked and would back away. But, almost every evening I'd go out and talk to him, bring him a carrot, corn on the cob and while he was munchin I'd blow the smoke up his nostrils. He seemed to get used to it and after the first couple times he didn't back away no more. Get High...well, maybe, not really sure as he was always real spirited. Smoke didn't seemed to make a difference in that regard.

okay, i'll stop thread jacking and diverting here

i have had my veg area on 20/4 for the past 2 weeks, honestly i can not tell at all if they are happier or not, growth seems to be somewhat constant so not much to report there. i like the bit of energy savings, i also feel that it may be best that they get a nap since the native environment would provide that for them so i'm running with this. thanks again for all the information everyone, from papers and from experience.

 

[llewop]

Great points, I am always intrigued by topics of photoadaptation. Would you mind citing some references for everyone to check out? [I would also like to read your references]

That information is from a textbook called Chronobiology: Biological Timekeeping. It was required reading for a biology class on circadian rhythms I took at UCSD. If your interested I'd be happy to send you the slides for the lecture on plant clocks along with an mp3 of the recorded lecture.

 

[Dr.Greenthmb420]

Photo Update

Photo Update

ALL VEGGED ON 18/6, pics are at 3 weeks 12/12!

 

[Unclepeter]

It's called a typo , I tend to make them from time to time because I type fast and tend to type a lot. I try to check my spelling and grammar, but sometimes things slip through. I really couldn't care less, considering this is an Internet forum and that you knew what I meant. I also tend to write "your" when I mean "you're", and "dont'" when I mean "don't", and even "teh" when I mean "the".

But please, continue pointing out typos, that is just what this thread needs, finally we have someone posting worthwhile info /sarcasm


FWIW, yes, cannabis is a C3 plant due to how cannabis fixes Co2 - carbon (re: RuBP). Cannabis is not a C4 plant. No one should be citing Ed.R.

what would you class corn as? C3 or C4? I have it as C4 just like tobacco... I'm fully aware of how RuBP opperates and I hope you are aware plants have the ability to be C4 within all of them its an evolutional step foward to remove the photorespiration which costs energy.

 

[Unclepeter]

You also make a good point about plants that carry out photorespiration. It used to be thought if C3 plants carried out any degree of photorespiration then photosynthesis is greatly hindered, but that is not the whole story. Plants normally carry out photorespiration from/during the process of nitrate metabolism. When C3 plants 'use' nitrate they naturally carry out a little bit of photorespiration. That said, if the plant carries out a lot of photorespiration then indeed, the rate of photosynthesis is greatly hindered. Photoinhibition (from light saturation) is one way to cause a plant to carry out too much photorespiration.

its wasting energy hence higher plants evolving to remove the process!.

O2 + RUBP --> 1 PGA + 1 Phosphogylcolate

Tell me does Cannabis thrive more in a hot humid enviroment or a moist cool one?

 

[spurr]

what would you class corn as? C3 or C4? I have it as C4 just like tobacco... I'm fully aware of how RuBP opperates and I hope you are aware plants have the ability to be C4 within all of them its an evolutional step foward to remove the photorespiration which costs energy.

I am well aware that maize is a C4 plant, and I am also well aware cannabis has never been found to have active C4 pathway (i.e., C4 cells in the C3 plant). Also, tobacco is a C3 plant, not C4, however, tobacco has been found to have C4 cell in the C3 plant (i.e., active C4 pathway).

note: this statement has not been proven: "...plants have the ability to be C4 within all of them...". It is a hypothesis that "all" C3 plants have the C4 pathway ability. If you can prove me wrong with peer-reviewed refs, please do so.

refs:


1. "Expression of photosynthetic genes from the C4 plant, maize, in tobacco"
Matsuoka M, Sanada Y
Mol Gen Genet. 1991 Mar;225(3):411-9


2. "Comparative Studies of Phosphoenolpyruvate Carboxylase from C3 and C4 Plants"
Makoto Matsuoka and Shingo Hata
Plant Physiol. (1987) 85, 947-951


3. "Regulation of Photosynthesis in C3 and C4 Plants: A Molecular Approach"
Robert T. Furbank and Wllliam C. Taylor
The Plant Cell, Vol. 7, 797-807 (1995)


4. "Photorespiration and C4 Plants"

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/C4plants.html

C4 cells in C3 plants

The ability to use the C4 pathway has evolved repeatedly in different families of angiosperms — a remarkable example of convergent evolution.

Perhaps the potential is in all angiosperms. A report in the 24 January 2002 issue of Nature (by Julian M. Hibbard and W. Paul Quick) describes the discovery that tobacco, a C3 plant, has cells capable of fixing carbon dioxide by the C4 path. These cells are clustered around the veins (containing xylem and phloem) of the stems and also in the petioles of the leaves. In this location, they are far removed from the stomata that could provide atmospheric CO2. Instead, they get their CO2 and/or the 4-carbon malic acid in the sap that has been brought up in the xylem from the roots.

If this turns out to be true of many C3 plants, it would explain why it has been so easy for C4 plants to evolve from C3 ancestors.

 

[spurr]

You also make a good point about plants that carry out photorespiration. It used to be thought if C3 plants carried out any degree of photorespiration then photosynthesis is greatly hindered, but that is not the whole story. Plants normally carry out photorespiration from/during the process of nitrate metabolism. When C3 plants 'use' nitrate they naturally carry out a little bit of photorespiration. That said, if the plant carries out a lot of photorespiration then indeed, the rate of photosynthesis is greatly hindered. Photoinhibition (from light saturation) is one way to cause a plant to carry out too much photorespiration.

its wasting energy hence higher plants evolving to remove the process!.

Higher plants (i.e., C3) have not "remove[d] the process!". Plants carry out a little photorespriation for nitrate metabolism.

Tell me does Cannabis thrive more in a hot humid enviroment or a moist cool one?

Tell me: why are you posting like you're trying to prove me wrong? It's one thing to disagree and try to point out misunderstandings, but trying to "trump" people with aggression (when it's unwarranted) is a fail. You were wrong about your claim of tobacco being C4 plant and your wrong about higher plants not carrying out a little photorespiration for nitrate metabolism.

Now to your loaded question: some cannabis ecotypes thrive in cooler (not cold) and less-humid (re: ideal VPD) environments and the majority thrive in warmer (not hot) more-humid (re: ideal VPD) environments. Also, as I assume you know, C3 plants under high irradiance and high Co2 have higher Pn under higher temps verses low irradiance and low (ambient) Co2. Also, VPD greatly affects Pn, thus when VPD is too high Pn is reduced...

 

[greenmatter]

when i first started this game i was at 24/0 .. at some point i switched to 18/6 and have stayed there ever since .. just seems like the girls like it better to me ...i will go with 24/0 to regen a cutting that was in flower but only for as long as it takes her to change her mind. we all do things a little different which is one of the cool things about this sight ... but i gotta admit it is fun watching folks like SPUR "bookslap" the shit out of some other folks. but then i only enjoy it because it is an entertaining way to pick up some great info. gotta like someone who throws down the bibliography to prove a point instead of just repeating what they have been repeating because it seems to work for them. it's in our nature to not see eye to eye but IMHO the guy with the facts does better in the end.

 

[Unclepeter]

Tell me: why are you posting like you're trying to prove me wrong? It's one thing to disagree and try to point out misunderstandings, but trying to "trump" people with aggression (when it's unwarranted) is a fail. You were wrong about your claim of tobacco being C4 plant and your wrong about higher plants not carrying out a little photorespiration for nitrate metabolism.

Now to your loaded question: some cannabis ecotypes thrive in cooler (not cold) and less-humid (re: ideal VPD) environments and the majority thrive in warmer (not hot) more-humid (re: ideal VPD) environments. Also, as I assume you know, C3 plants under high irradiance and high Co2 have higher Pn under higher temps verses low irradiance and low (ambient) Co2. Also, VPD greatly affects Pn, thus when VPD is too high Pn is reduced...

where have I been aggressive? you like to tell people they are wrong alot don't you? I will say perhaps I shouldn't say cannabis is C4 per sa but its not C3 either IMO some say it acts more C3 in hydro and more C4 in soil so for me C4.

Also, tobacco is a C3 plant, not C4, however, tobacco has been found to have C4 cell in the C3 plant (i.e., active C4 pathway)

agreed.

but these plants are evolving hence I'd class it as intermediate(some seem to use a few diff systems within the cycle).

http://eprints.whiterose.ac.uk/113/1/quickwp1.pdf

I am well aware that maize is a C4 plant, and I am also well aware cannabis has never been found to have active C4 pathway (i.e., C4 cells in the C3 plant). Also, tobacco is a C3 plant, not C4, however, tobacco has been found to have C4 cell in the C3 plant (i.e., active C4 pathway).

your arrogance astounds me, you start my saying you are well aware etc, yet I asked a question I didn't point someting out did I?

C4 carbon fixation has evolved on several occasions in different groups of plants, so is an example of convergent evolution. Plants which use C4 metabolism include sugarcane, maize, sorghum, Eleusine, Amaranthus, Euphorbia, and Cannabis. C4 plants are known only since the Cenozoic and did not became common until the Miocene. Today they represent about 5% of Earth's plant biomass.

http://bookjob.vn/tempfile/00_bookjob.vn_Handbook_Of_Plant_And_Crop_Physiology_2422.pdf

http://www.spiritus-temporis.com/c4-carbon-fixation/

You were wrong about your claim of tobacco being C4 plant and your wrong about higher plants not carrying out a little photorespiration for nitrate metabolism.

I'll take the point on tobacco though I now have it as intermediate.

The problem of photorespiration is overcome in C4 plants by a two-stage strategy that keeps CO2 high and oxygen low in the chloroplast where the Calvin cycle operates. The class of plants called C3-C4 intermediates and the CAM plants also have better strategies than C3 plants for the avoidance of photorespiration.

http://hyperphysics.phy-astr.gsu.edu/hbase/biology/phoc.html

and more on intermediates.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1054379/

and for any french speaker out there!

http://fcf.cannaweb.org/fcf/viewtopic.php?p=1116905&sid=13bda8a41ae34446f21b7930acf4d24e

higher plants want to avoid the waste of energy, like I will with you.

 

[Frozenguy]

I do not know the degree to which it is reduced, but I think after the plant converts photosynthate into starches (via light independent reactions) the rate of photosynthesis could climb back up, but I am not sure. I plan to study this once I get a chlorophyll fluorometer in early next year.

So one needs a chlorophyll fluorometer to figure out when the plant is photosynthesizing or doing light independent processes? This is the cheapest/easiest way?
Otherwise how do we know how much light to give each set of plants if we dont know how long the 24h plants stop/reduce photosynthesis and at what rate.

Yea, maybe you should try lower again. A good study looking at CO2 supplemented chamber (at 750 ppm) and ideal high irradiance (at 1,500 PPFD) found ~86'F to be the peak rate of photosynthesis for a few different varieties of cannabis.

In regard to the section from that article you quoted, it's true Rubisco can function properly above 100'F, but once the Rubisco is made inactive (via process of photosynthesis), it can not be made active again (to keep rate of photosynthesis high all day) unless there is sufficient Rubisco activase. And if the Rubisco activase is not sufficient, ex. from too high temps, the conversion of inactive Rubisco into active Rubisco will be hindered, and that means the net rate of photosynthesis (over the whole day) will be reduced.

I have a few other studies looking at temp effects on Rubscio activase and they found ~90'F can negativity effect Rubisco activase. But, I haven't looked into this for maybe a year or two, so there might be more studies on this topic. I will look for additional studies, hopefully some on Arabidopsis thaliana, which is the most widely used C3 plant "model organism" by plant scientists.

I have info on how to use TLC to test for Rubisco and IIRC Rubisco activase, and I can use TLC in a comparive manner. Thus I could test a few groups of plants under the same irradiance (e.g. 1,500 PPFD), Co2 (e.g., 1,000 ppm) and close to the same VPD* (e.g. 1.25 kPa); all with different canopy temps. I can also use a chlorophyll fluorometer to test the rate of photosynthesis for each group.

* I would try to keep VPD from 1.25-1.3 kPa because keeping VPD much over 1.25 kPa can reduce stomatal conductance too greatly. That in turn can negatively effect rate of transpiration, Co2 fixation, rate of photosynthesis and leaf cooling ability (via reduced transpiration), etc. Off the top of my head am thinking I could test leaf Rubisco activase at 86'F (with 70% RH = 1.27 kPa), 88'F (with 72% RH = 1.26 kPa), 90'F (with 73% RH = 1.28 kPa) and 92'F (with 75% RH = 1.26 kPa).

So you're saying that even though Rubisco still works effectively at 92f, the quantity of Rubisco activase starts to suffer so it can't reactivate the inactive Rubisco? So what do you think would help increase Rubisco activase at 92f?

Cant one consider VPD as a drying factor if you will? The higher the VPD, the less water vapor in the air, so less pressure between the two and it lends to the plant transpiring at an increased rate.
RH has always been a factor thats difficult to control in my rooms.. Too dry..
I can't find my laser thermometer, so a rough estimate of my vpd is ~2.27[kPa]

Damn..

 

[spurr]

where have I been aggressive? you like to tell people they are wrong alot don't you?

In your posts to me. And no, I do not like telling people they are wrong, but I do so when it's appropriate, and I expect the same in return (with legit refs, that is).

You are Kopite reincarnated, and that's why you posted to me like you did; and why you got the response you got from me...

I will say perhaps I shouldn't say cannabis is C4 per sa but its not C3 either IMO some say it acts more C3 in hydro and more C4 in soil so for me C4.

You can say it's C5,000,000 if you want, but that doesn't make you correct. Cannabis spp. is a C3 genus, it's as simple as that, no need to try and imagine it being more complex to 'prove' your point.

Cannabis may have active C4 pathway, which AFAIK has not been proven, but even if it does, that does not mean it's C4, nor C3-C4 intermediate; it just means it's C3 with active C4 pathway.

Also, tobacco is a C3 plant, not C4, however, tobacco has been found to have C4 cell in the C3 plant (i.e., active C4 pathway)

but these plants are evolving hence I'd class it as intermediate(some seem to use a few diff systems within the cycle).

http://eprints.whiterose.ac.uk/113/1/quickwp1.pdf

If you could properly cite your references it would be helpful. I read that study a while ago, and would have preferred not to have to download it to find out the title.

You can classify tobacco anyway you like, but that doesn't make you correct. Tobacco is a C3 plant with active C4 pathway. Everything is still evolving, all the time, but until it actually is a C4 plant, it's at least a C3 plant. Yes, there is a classification of species called "C3-C4 intermediate", and AFAIK tobacco does not fall under that classification, but it's off topic here anyway.

your arrogance astounds me...

Good, I was worried you were not astounded; that's a load off my mind. /sarcasm

C4 carbon fixation has evolved on several occasions in different groups of plants, so is an example of convergent evolution. Plants which use C4 metabolism include sugarcane, maize, sorghum, Eleusine, Amaranthus, Euphorbia, and Cannabis. C4 plants are known only since the Cenozoic and did not became common until the Miocene. Today they represent about 5% of Earth's plant biomass.

http://bookjob.vn/tempfile/00_bookjob.vn_Handbook_Of_Plant_And_Crop_Physiology_2422.pdf

http://www.spiritus-temporis.com/c4-carbon-fixation/

The first link is broken and the second link is not legit. Not only is some of the info from the second link copied from this Wikipedia article, but the rest of the info on the page is not referenced, and thus not valid. I would not trust the claim you quoted from the second link as far as I could throw it.

I would be very happy to learn cannabis has active C4 pathway, but so far I have not seen such a claim from a valid resource. My mind if open and I would like to know if I am wrong, but please, use legit references.

You were wrong about your claim of tobacco being C4 plant and your wrong about higher plants not carrying out a little photorespiration for nitrate metabolism.

I'll take the point on tobacco though I now have it as intermediate.

Tobacco is a C3 plant and AFAIK it's not a C3-C4 intermediate. Your own refence seems to agree tobacco is a C3 plant, not a C3-C4 intermediate:

"Characteristics of C4 photosynthesis in stems and petioles of C3 flowering plants"
Julian M. Hibberd and W. Paul Quick
NATURE, vol. 415 (2002)
​

Can we now get off the topic of C4 and C3-C4 intermediate plants? I ask because cannabis is neither, so this discussion is not only moot, but off topic.

 

[spurr]

I do not know the degree to which it is reduced, but I think after the plant converts photosynthate into starches (via light independent reactions) the rate of photosynthesis could climb back up, but I am not sure. I plan to study this once I get a chlorophyll fluorometer in early next year.

So one needs a chlorophyll fluorometer to figure out when the plant is photosynthesizing or doing light independent processes?

No, there are other methods. But using a Chl fluorometer to find rate of photosynthesis from the photons leaves emit is well proven and fairly cheap verses a photosynthesis chamber (measuring gas exchange, etc.).

This is the cheapest/easiest way?

For reasonable quantitative accuracy, yes, to my knowledge.

Otherwise how do we know how much light to give each set of plants if we dont know how long the 24h plants stop/reduce photosynthesis and at what rate.

Yea, that's the problem. We need to track Pn over a whole day (Pnnet) accounting for DLI, PPFD, VPD, etc., to see when Pn drops/stalls. We can also test carbon assimilate every X hours over the day, e.g., the basic starch test, to compile more info on light-independent reactions.

Yea, maybe you should try lower again. A good study looking at CO2 supplemented chamber (at 750 ppm) and ideal high irradiance (at 1,500 PPFD) found ~86'F to be the peak rate of photosynthesis for a few different varieties of cannabis.

In regard to the section from that article you quoted, it's true Rubisco can function properly above 100'F, but once the Rubisco is made inactive (via process of photosynthesis), it can not be made active again (to keep rate of photosynthesis high all day) unless there is sufficient Rubisco activase. And if the Rubisco activase is not sufficient, ex. from too high temps, the conversion of inactive Rubisco into active Rubisco will be hindered, and that means the net rate of photosynthesis (over the whole day) will be reduced.

I have a few other studies looking at temp effects on Rubscio activase and they found ~90'F can negativity effect Rubisco activase. But, I haven't looked into this for maybe a year or two, so there might be more studies on this topic. I will look for additional studies, hopefully some on Arabidopsis thaliana, which is the most widely used C3 plant "model organism" by plant scientists.

I have info on how to use TLC to test for Rubisco and IIRC Rubisco activase, and I can use TLC in a comparive manner. Thus I could test a few groups of plants under the same irradiance (e.g. 1,500 PPFD), Co2 (e.g., 1,000 ppm) and close to the same VPD* (e.g. 1.25 kPa); all with different canopy temps. I can also use a chlorophyll fluorometer to test the rate of photosynthesis for each group.

* I would try to keep VPD from 1.25-1.3 kPa because keeping VPD much over 1.25 kPa can reduce stomatal conductance too greatly. That in turn can negatively effect rate of transpiration, Co2 fixation, rate of photosynthesis and leaf cooling ability (via reduced transpiration), etc. Off the top of my head am thinking I could test leaf Rubisco activase at 86'F (with 70% RH = 1.27 kPa), 88'F (with 72% RH = 1.26 kPa), 90'F (with 73% RH = 1.28 kPa) and 92'F (with 75% RH = 1.26 kPa).

So you're saying that even though Rubisco still works effectively at 92f, the quantity of Rubisco activase starts to suffer so it can't reactivate the inactive Rubisco? So what do you think would help increase Rubisco activase at 92f?

Yes exactly, well put. There is nothing I know of that will increase amount of Rubisco activase if temp is kept past the point that hinders Rubisco activase. Also, Rubisco activase in some genus or species could be active at temps higher than 92'F, I have not read info specific to cannabis about Rubisco activase, but I consider 90-92'F to be a reasonable Rubisco activase point of hindrance.

Even in high Co2 environments (i.e., 750 ppm) with peak level of PPFD (i.e., 1,500), ~86'F provided highest Pn. Also, over ~85'F hindered Pn of cannabis in a few studies (that did not study Co2 affects on Pn). No studies I am aware found that > 86'F is ideal for cannabis, even with Co2 and high irradiance.

Cant one consider VPD as a drying factor if you will? The higher the VPD, the less water vapor in the air, so less pressure between the two and it lends to the plant transpiring at an increased rate.

Yes, that could be one way to look at it. However, once E (rate of transpiration) exceeds a critical level the leaves reduce stomatal conductance (Gs) either by the "feed-forward" hypothesis or the "feed-back" hypothesis. Thus, once VPD gets too high, the leaves take action to prevent the plant from 'drying out' by reducing Gs. Also, if VPD is too low, the leaves will reduce Gs.

RH has always been a factor thats difficult to control in my rooms.. Too dry..
I can't find my laser thermometer, so a rough estimate of my vpd is ~2.27[kPa]

Damn..

Yea, that's pretty high, but not the highest I have seen; a buddy grew/grows with RH at ~25% and temp at ~75'F! Cannabis grows fine at higher VPD, but from my experience, and that of others I have helped with VPD, once VPD is lowered the plants fare better. Other bonuses to controlling VPD is more efficient Ca and Bo usage by plants (both are dependent upon E for uptake into roots), higher Co2 fixation, etc.

The reason you might have a real hard time getting near 1.25 kPa is you keep your room so hot. The hotter the room, the more water vapor the air holds, and thus, the higher the RH must go until the goal VPD is reached. In a room that is kept at ~80'F the RH will be a lot lower than in a room kept at ~92'F, when both rooms have the same VPD.

 

[somoz]

Back To The Future

Back To The Future

Doc Brown called, he'd like his flux capacitor and science books back.

 

[Unclepeter]

where have I been aggressive? you like to tell people they are wrong alot don't you?

In your posts to me. And no, I do not like telling people they are wrong, but I do so when it's appropriate, and I expect the same in return (with legit refs, that is).

You are Kopite reincarnated, and that's why you posted to me like you did; and why you got the response you got from me...


You can say it's C5,000,000 if you want, but that doesn't make you correct. Cannabis spp. is a C3 genus, it's as simple as that, no need to try and imagine it being more complex to 'prove' your point.

Cannabis may have active C4 pathway, which AFAIK has not been proven, but even if it does, that does not mean it's C4, nor C3-C4 intermediate; it just means it's C3 with active C4 pathway.




If you could properly cite your references it would be helpful. I read that study a while ago, and would have preferred not to have to download it to find out the title.

You can classify tobacco anyway you like, but that doesn't make you correct. Tobacco is a C3 plant with active C4 pathway. Everything is still evolving, all the time, but until it actually is a C4 plant, it's at least a C3 plant. Yes, there is a classification of species called "C3-C4 intermediate", and AFAIK tobacco does not fall under that classification, but it's off topic here anyway.

So where I put agreed you just argued for the sake of what exactly?

Good, I was worried you were not astounded; that's a load off my mind. /sarcasm


The first link is broken and the second link is not legit. Not only is some of the info from the second link copied from this Wikipedia article, but the rest of the info on the page is not referenced, and thus not valid. I would not trust the claim you quoted from the second link as far as I could throw it.

I would be very happy to learn cannabis has active C4 pathway, but so far I have not seen such a claim from a valid resource. My mind if open and I would like to know if I am wrong, but please, use legit references.



Tobacco is a C3 plant and AFAIK it's not a C3-C4 intermediate. Your own refence seems to agree tobacco is a C3 plant, not a C3-C4 intermediate:

"Characteristics of C4 photosynthesis in stems and petioles of C3 flowering plants"
Julian M. Hibberd and W. Paul Quick
NATURE, vol. 415 (2002)
​

Can we now get off the topic of C4 and C3-C4 intermediate plants? I ask because cannabis is neither, so this discussion is not only moot, but off topic.

i'll let people come to THEIR own conclusion and to do their own research not to take anything you say as gospel- now go write your book!! funny how you class something as you like then call me for doing so, keep taking the medicine!.

I have yet to read cannabis is classified (re: taxonomic) as sub-dioecious (having some plants that are monoecious, ala hermi plants) except by one guy at ICmag, englishrick. I noticed you too posted to Icmag in some of those threads. Can you post sources of info showing why you feel that way (hopefully academic, peer reviewed sources)?

I can see why you do classify cannabis as sub-dioecious though, considering the hermi tendency in some strains(cultivars)/varieites/races; however, I don't know if I would call the whole genus Cannabis sub-dioceious considering hermi tendencies usually come from stress, not very often from unstressed plants. Alaska, what is your take on this topic?

Monoecious plants can be unisexual, AFAIU they are called consecutively monoecious (one sex at a time), otherwise they are called simultaneously or synchronously monoecious (both sexes at the same time). Please see these references:

Sex Determination in Monoecious and Dioecious Plants
by Erin E. Lrish and Timothy Nelson
The Plant Cell, Vol. 1, 737-744, August 1989
(paragraph 5, sentence 4)
http://www.plantcell.org/cgi/reprint/1/8/737.pdf​

...and even though I really dislike Wikipedia I will offer the page on plant sexuality because it is pretty well written IMO:

Plant sexuality
https://secure.wikimedia.org/wikiped...lant_sexuality​

I'm sure you remember that post, don't ya? before you erased them all in your hissy fit! see you say with regard to wiki

I would not trust the claim you quoted from the second link as far as I could throw it..

yet here you used it againts myself that makes you 2 faced and I don't trust or like people like that!.

 

[Dr.Greenthmb420]

Vegging "correctly" in 18/6 with proper spectrum equals this

Vegging "correctly" in 18/6 with proper spectrum equals this

TASTE THE PUDDING

 

[spurr]

Can we now get off the topic of C4 and C3-C4 intermediate plants? I ask because cannabis is neither, so this discussion is not only moot, but off topic.

i'll let people come to THEIR own conclusion and to do their own research not to take anything you say as gospel- now go write your book!! funny how you class something as you like then call me for doing so, keep taking the medicine!.

I didn't classify cannabis as C3 and tobacco as C3, that was done a long time ago by scientists studying the plants. I don't go off willy-nilly on my own making up classifications for plants to suit my pre-conceived notions; unlike yourself. I rely upon science, not wishful thinking and hoping.

If it's proven cannabis has C4 pathways, great, I would be happy to learn; and if it's proven cannabis is really a C3-C4 intermediate genus, great, I would be happy to learn. And in neither case would I try to refute well proven, sound science with my own conjecture; unlike what you are doing.

I have yet to read cannabis is classified (re: taxonomic) as sub-dioecious (having some plants that are monoecious, ala hermi plants) except by one guy at ICmag, englishrick. I noticed you too posted to Icmag in some of those threads. Can you post sources of info showing why you feel that way (hopefully academic, peer reviewed sources)?

I can see why you do classify cannabis as sub-dioecious though, considering the hermi tendency in some strains(cultivars)/varieites/races; however, I don't know if I would call the whole genus Cannabis sub-dioceious considering hermi tendencies usually come from stress, not very often from unstressed plants. Alaska, what is your take on this topic?

Monoecious plants can be unisexual, AFAIU they are called consecutively monoecious (one sex at a time), otherwise they are called simultaneously or synchronously monoecious (both sexes at the same time). Please see these references:

Sex Determination in Monoecious and Dioecious Plants
by Erin E. Lrish and Timothy Nelson
The Plant Cell, Vol. 1, 737-744, August 1989
(paragraph 5, sentence 4)
http://www.plantcell.org/cgi/reprint/1/8/737.pdf​

...and even though I really dislike Wikipedia I will offer the page on plant sexuality because it is pretty well written IMO:

Plant sexuality
https://secure.wikimedia.org/wikiped...lant_sexuality

​

I'm sure you remember that post, don't ya? before you erased them all in your hissy fit! see you say with regard to wiki yet here you used it againts myself that makes you 2 faced and I don't trust or like people like that!.

Yes I do, and I didn't 'erase' my posts from TCC. I was banned from TCC and the admin deleted all my posts, that was not my doing. The admin and some members at TCC (like Dcyans) disliked learning they are/were wrong about many claims they hold as unassailable truths. That is why I was banned, because I feel it's important to correct common misconceptions, and that made me a few enemies; just like it has done here and at C-W2 (e.g., Cray hating the fact he is wrong).

You however did erase your posts when you deleted your account here as Kopite. Just to come back as uncleclepter, with the same attitude you had as Kopite.

What I find funny about you citing that post of mine is: (1) in that post/thread I proved you wrong that cannabis is an obligate outcrossing genus; and (2) I only posted a link to Wikipedia after writing that Wikipedia is not a good reference source, I only posted it because the info was well written and I verified it's accuracy before hand.

When I proved you wrong about your claim that cannabis is an obligate outcrossing genus, that was the nexus of your animosity toward me. You still haven't let it go that I proved you wrong many, many months ago; that's pretty damn sad, man. You should try to like when you are proven wrong, then you can become right.

I am not two faced. I posted a wikipedia article after I wrote the caveat that wikipedia should not be trusted (at face value). Then in this thread I took issue with your usage of a copyright-infringing copy/paste from parts of a wikipedia article because you tried to cite it as a legit scholarly reference (which I did not do when I posted the wikipedia article).

I would not trust the claim you quoted from the second link as far as I could throw it.

see you say with regard to wiki yet here you used it againts myself that makes you 2 faced and I don't trust or like people like that!

You are confusing matters, again. What you quoted from that second link of yours (re: cannabis having active C4 pathway) was not from the Wikipedia article. The claim about cannabis was unreferenced, which is why I wrote: "I would not trust the claim you quoted from the second link as far as I could throw it." Please, when you assail me with bull*hit, at least get your facts straight...ummkay?

Kopite, I am done responding to you. You are here to try and prove me wrong, no matter how wrong you are in the process, and each time you have failed in your goal. I would be happy to learn I am wrong about something, ex., C3 vs. C3-C4, but to prove it you must properly cite legit references, not your wishful thinking and conjecture.

 

[spurr]

TASTE THE PUDDING

Nice pics.