Why go 24 hours lights on??

[smokefrogg]

...NOONE CAN DISPUTE MY RESULTS, YOU CAN LEAD A HORSE TO WATER, BUT CANT FORCE IT TO DRINK. LET SEE YOUR PIC. LOL

 

[jeffie]

u nowhere near this dude

 

[Dave Coulier]

Watch out Sam my brotha, one of the admins hate anyone who is pro 24/0 light cycle. Removed the picture and proof from Bob and Rumple. Lots of folks showing cool proof of no dark cycle but all get removed. Can't keep the truth in the dark.

My plants grow 33% faster with out that Calvin dude helping (how is that possible?). Did um both ways 18/6 much slower and un-healthy. My 24/0 plants are much bigger and finish with more bud.

Did it both ways and know the truth.


**read it quick**

If you have unhealthy slow growing plants using 18/6 then its grower error. Its what I use, and Ive got pictures of 23 day old seed plants that are beautiful, and fast growing in my Lemon Grass Thai X Deep Chunk album. Feel free to check them out.

And with regards to pictures of 'proof'. Those pictures are proof the plants can be grown without a dark cycle, but it is not proof that they fare better without one. One should not confuse the two.

 

[Dr.Greenthmb420]

LMAO

LMAO

LOL this guy is flowering for 81 days LMAO, Im Done in almost 3/4 that time. LOL, If flowering is taking that long then Im sure your Vegging is horribly long too. Still LMAO BY THE WAY Light On and Off pics below to show the difference in Color. LOL

 

[Phedrosbenny]

I have allways vegged at 24/0.Thought about changing it to see what the results would be.Maybe ill give 18/6 a try.If it slows things down im back to 24/0 though.

 

[GanjaPharma]

i do see faster growth in 20/4 than in 18/6 but there is one situation where i have found 24hr light to be helpful.
when taking clones from a flowering plant (up to 2 weeks in) they sometimes need convincing that they are back in VEG. 18/6 can result in these clones doing wonky stuff like throwing single bladed leaves and irregular inter-nodal development. so 24 hours for a few weeks till they look normal again...then i'm back to 20/4 or 18/6.

i suppose i do the same when re-vegging ....

 

[smokefrogg]

u nowhere near this dude

hehehehe laughing my ass off over here, nice one jeffie =)

 

[Bubba2]

LOL this guy is flowering for 81 days LMAO, Im Done in almost 3/4 that time. LOL, If flowering is taking that long then Im sure your Vegging is horribly long too. Still LMAO BY THE WAY Light On and Off pics below to show the difference in Color. LOL

Yo, can anyone point out to this fool that flowering is not the same from strain to strain. He thinks he is full of the skillz cuz his plant are ripe before mine. Lots of Sativas need 90 or more days.
I bet you are cut'n down your little plants early.

Most good growers flower longer then noobs. They know whaz up.

I veg the same as Rumple. 10 days and that is it. Sure my stuff is not as heavy but he uses CO2.

Damn da noobs are buggin

Lol *Snap!* Read the post below this one....

 

[smokefrogg]

LOL this guy is flowering for 81 days LMAO, Im Done in almost 3/4 that time. LOL, If flowering is taking that long then Im sure your Vegging is horribly long too....

?!?

maybe i misread or something, but man i gotta' tell you, i've some thai here that starts looking ready at 12/13 weeks, i've taken it at 16 weeks and it was awesome. flowering time completely varies strain to strain. the petrolia headstash i cut today was readyish @ 68 days, the afghan x lowryder #2s need however take way longer to finish (weird ass genetics, so not short like regular lowryder #2 lol, defeats the purpose kinda', still yummy stuff though! *berries!*)

...also! with that logic i guess the sun sucks, haha, there are some outdoor jamaican girls flowering right now at a caregiver's place i'm visiting soon, these things are nowhere near done, and it's december! lol, probably end of january or something maybe they'll be ready

 

[FreezerBoy]

LOL this guy is flowering for 81 days LMAO, Im Done in almost 3/4 that time.

Dude, guys who finish fast don't brag about it, they go see their doctor! At 120 days, my trichs are still clear.

 

[smokefrogg]

Dude, guys who finish fast don't brag about it, they go see their doctor! At 120 days, my trichs are still clear.

bwahahaha! MOTED!!

 

[zeke99]

@ 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.

 

[llewop]

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...

 

[OVERMAN]

not firing the bulb off and on is better for it and the plants seem to grow alot faster then in 18-6

 

[303hydro]

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...

Def worth mentioning, I noticed the slower turn when we switched to 24/7....

 

[spurr]

Nope, plant rate of photosynthesis is reduced after about the 17th-18th hour of non-stop light. At that point much of the active rubisco has been converted into inactive rubisco, which means the plants can't keep up high rate of photosynthesis, because rubisco activase is less able to 'do it's job' under 24/0. Also under 24/0 C assimilate/partitioning goes down past the 17th-18th hours, as well as Co2 fixation, etc.

You described it well when you wrote about how plants need to 'switch' modes (excuse my simple description) to carry out light independent reactions such as starch conversion, cellular repair, etc., if light is provided 24/0. Plants simply can't use light to photosynthesize and carry out other needed reactions simultaneously, and keep up a high rate of photosynthesis.

So, do we know, at what rate the plant is photosynthesizing after about 18 hours; and for how long this reduced rate is sustained?
I have to assume its substantially reduced.. One would have to know the rate, roughly, if one were to attempt to test this.

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.

This topic is also why using Co2 over ~1,200 ppm is bad, as well as temps over ~89'F. In both instances the amount of rubisco activase is reduced, thus the plant is less able to convert inactive rubisco into active rubisco. That means the rate of photosynthesis goes way down and the plant suffers (just like if using 24/0 of light). I have a few studies on cananbis that looked at ideal level of Co2, along with PPFD and temp, all found Co2 saturation at ~> 1,000 ppm, just like most other C3 plants. Thus using more than 1,000 ppm is a waste, and using more than 1,200 ppm can/does hinder rate of photosynthesis due to reduction of rubisco activase. That is another area of BS in the cannabis world, i.e. claims that 1,500 ppm of Co2 is ideal (that has never been proven, it's only more conjecture and anecdotal evidence from 'first hand experience' so loved by some in this thread). Check out this thread for more info I wrote on that topic: "A simple question for growers that use CO2"

"Robust Plants' Secret? Rubisco Activase!"
Steven J. Crafts-Brander and Micheal E. Salvucci
Agricultural Research Magazine, Nov. 2002, Vol. 50, No. 11
http://www.ars.usda.gov/is/ar/archiv.../plant1102.htm

I usually run at about 92F when applying CO2, just what I've found best from 88,92, 95, 97.. Maybe I should of tried 90 hah.. But I also read this in that link

"Denaturing of rubisco activase can occur at temperatures as low as 89.6°F. But rubisco continues to function effectively until temperatures reach 131°F, Crafts-Brandner and Salvucci found."
​

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).

 

[brandon.]

The reason I chose to use 18/6 over 24/0

Quick refresher.

Photosynthesis - makes food for your plant, stores it, uses h2o, uses co2 etc.
Respiration - Uses the stored food and energy, produces h2o and co2, etc.

Photosynthesis is light dependent, so it only happens during your lights on period. Respiration on the other hand is not dependent on light, so it happens during lights on and off. It's not that the plants "need to sleep", it's that during lights out they're not pulling double duty. They can just work on respiration using the stored food and energy to grow big and strong!

 

[spurr]

First of all I have used 24 hours veg for over 20 years, I did experiments with dry weight yields and Cannabinoid total yields at both 24 and 18/6 and then flowered at 12/12. 24 gave higher yields, what can I say?

Did you measure irradiance as PPFD (used to be called PAR)? And DLI?

Were the plants better off under 18/6, maybe but I did not see 24 as a real problem for them in any way.

I agree, 24/0 is not a "real problem for them", but 18/6 should be better if DLI is the same. That in turn should make healthier plants due to night period. It's not measured in miles, but inches and maybe feet. But, as they say, the little things add up...

I also in my greenhouse used 60 w blue grow incancesdents one per 10 square meters or about 100 square feet in the winter at night with natural sunlight as photoperiod correction for large veg mother plants. Never lost a single mother, they very slowly grow all winter, which is what I wanted it was my plant library. They only correct photoperiod.

That's odd, if you only used blue light, and no far-red, that should not have kept the plant thinking the day is long, due to lack of far-red phytochrome (i.e., phytochome B, aka Pfr) reaction from far-red light. I assume because you used an incandescent lamp (which gives off a lot of far-red), even though it was painted(?) blue, far-red still was reaching the plants. Otherwise, if you only provided blue light, and no far-red at all, it could have been due to crytochrome* response effects on photoperiodism of the cannabis.

* cryptochrome are blue light receptors in plants, the effect of cryptochrome responses on photoperiodism are not well understood yet, but there is evidence it does have an effect. Cryptochrome is to blue light what phytochrome is to red and far-red light. That said, phytochrome B (i.e. Pfr; far-red light of ~720-740 nm) has a far bigger effect upon photoperiodism (re: the plant sensing length of night) than does cryptochome.

I also grow small mothers under 8-10 C with the lights on for 2 hours then off for 6 and the plants stay alive, slowly grow and stay veg for 6 months at a time. This is in a refrigerated/heated TL lighted grow chamber.

What is 8-10 C? Do you mean Celsius? If so, wow, that is cold!

On the topic of using light on for X hours, off for Y hours then back on for X hours, and so on; growth is slowed (even in sufficient temps) due to rate of photosynthesis. Someone asked about using flip-flop light schedule, and I refused to answer him because he was being a troll. But I feel fine about putting in my 2cents for you, I respect you a lot:

In terms of using light on for 2 hours, then off for 6 hours, and back on for 2 hours and off for 6 hours, and so on, the "steady-state" rate of photosynthesis will not be high enough to provide high net rate of photosynthesis. The reason is, for cannabis (and most other plants) it takes a little while for them to reach a high rate of photosynthesis at steady-state, even under ideal irradiance from the time of light-on. Cannabis usually takes about 30-45 minutes to reach peak rate of photosynthesis and steady-state photosynthesis under high irradiance. That means if you used only 2 hours of on time, the plants only got 75-90 minutes of peak rate of photosynthesis; which isn't long at all. That would definitely reduce the net rate of photosynthesis, and thus reduce rate of growth, even in suffeinct temps. If using flip-flop light schedule (i.e. on-off-on-off-on-off all day) using an on time of at least four hours is a good idea. That said, using flip-flop light schedule is not a good idea in terms of net rate of photosynthesis.

I am sure that none of this is the very best for them, it is what is best for me, and I can't find the negative effects of any of them.

Most of the time, if the negative effect is not apparent when measuring rate of growth, then the negative effect is on rate of photosynthesis, net rate of photosynthesis, carbon fixation, etc.

I don't really grow under lights, I use the sun and kinda laugh when people using artificial lights make claims about which artificial light is best, be honest the sun is best for many reasons starting with the lack or minimal of carbon footprint.

I agree with part of that quote, re: carbon foot print. I for one off-set my carbon footprint from growing indoor, in fact, I have a negative carbon footprint from growing indoors by buying carbon credits to off-set my electric usage.

The part I do not agree with is the part that growing under the sun is better than growing under HID (when done properly). Growing under HID can allow a grower to provider higher DLI in shorter time, with higher irradiance while not reaching "photosaturation". The issue of photosaturation often happens outdoors in the summer around noon when PPFD is > 1,600; it causes "photoinhibition" which in turn causes "midday depression of photosynthesis" and sometimes "multi-peak photosynthesis". All of those negative effects on photosynthesis reduces net rate of photosynthesis and hinders plant growth and can hinder plant health.

Growing indoors we can also provide ideal VPD (i.e. "Air-to-Leaf Vapor Pressure Deficit") and ideal Co2 (i.e. 1,000 ppm), both of which mean better plants with higher growth rates, higher rate of photosynthesis, etc. Not only that, but indoors we can provide ideal DIF and ideal level of UV-b to increase THC production a good deal, along with increasing production of flavonoids and possibly some terpenoids. Using a lamp like the Hortilux Blue, we can provide great light quality (lots of green, sufficient blue and sufficient red; mimicking ideal PAR range sunlight), along with high irradiance (dependent upon distance to canopy). Other lamps like the Ushio Combo 1,000w are also a big step forward.

Growing Cannabis under lights is just not right to me, I know many will say WTF? But I refuse to flower under lights, I know you can, but I choose not to as it is not needed. If you live in an area where you must keep cultivation private I understand the need, but it it because of the laws not what is best for the plant or planet.

I would not say "WTF?"

You make good points that are valid for most indoor growers. However, for indoor growers who know how to create ideal an growing environment for cannabis, which isn't possible outdoors for 99% of outdoor growers, I would simply disagree with you. And for growers who off-set their grow room's carbon footprint, the point about what is best for the earth can be made moot.

If for one think the best option is a fully controlled greenhouse with Co2 injection, DIF control, VPD control, UV-b supplementation, HID supplementation for when the sun isn't providing enough irradiance, and shade covers for when the sun is providing too much irradiance, etc, etc.

How much electricity do you think is consumed daily worldwide growing Cannabis? I am sure it is enough to be concerned about the effects the electrical production causes for us all.
-SamS

I agree 100%, that is why I buy carbon credits: to off-set my grow room's carbon footprint from electric usage. I think more growers should also do what I do. In fact, by creating a negative carbon footprint for my grow room, I suggest I might be having a less harmful impact upon the environment (i.e. greenhouse gases) than outdoor growers who need to drive their vehicles to their grow spot, use diesel generators, etc.

 

[spurr]

The reason I chose to use 18/6 over 24/0

Quick refresher.

Photosynthesis - makes food for your plant, stores it, uses h2o, uses co2 etc.
Respiration - Uses the stored food and energy, produces h2o and co2, etc.

Photosynthesis is light dependent, so it only happens during your lights on period. Respiration on the other hand is not dependent on light, so it happens during lights on and off. It's not that the plants "need to sleep", it's that during lights out they're not pulling double duty. They can just work on respiration using the stored food and energy to grow big and strong!

I agree 101%! One neat point though: plants continue to photosynthesize for a little while after lights go out, normally for up to about 30 minutes or so.

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.

 

[spurr]

Because artificial lighting CAN NOT completely replace the natural light of the sun... Yet. We create an artificial environment for indoor grows but it is still lacking. So to compensate for the insufficient quality of light we compensate with quantity.

That is not accurate. It's very easy to provide better light than the sun, in both light quantity (i.e. irradiance, aka intensity) and light quality (i.e. spectrum). The whole PAR range of light (i.e. 400-700 nm) drives rate of photosynthesis well, even green light, which under high irradiance white light (ex. sun, HID, etc) can drive rate of photosynthesis more than blue and red light (via acting upon chloroplasts in lower section of leafs).

There are many things an indoor grower can do to make their grow better than what can happen outside. And growing outside, especially in mid-late summer below the far north, the sun often gets too bright (i.e. > 1,600 PPFD) for too long, which causes a chain reaction that leads to "midday depression of photosynthesis".

See the following post of mine for lots more info:
https://www.icmag.com/ic/showpost.php?p=4101804&postcount=558
​

Also, outdoor the VPD is often far too high around noon (due to low RH and high temp) which also leads to "midday depression of photosynthesis". VPD can also be too high indoors from low RH and high temp. When VPD gets too high rate of photosynthesis is greatly reduced, along with Co2 fixation, rate of transpiration, etc., because stomatal conductance is too greatly reduced.

See this post of mine for more info, and see the VPD thread in the science sub-forum for lots of info I posted:
https://www.icmag.com/ic/showpost.php?p=4101721&postcount=556
​