Max PPF/PPFD with and without Co2

Have2

Have2

Well-Known Member
1000 ppfd in veg... Fuck, that is insane!

I usually go at 300-400 ppfd in veg... Going at 500-600 and they look exhausted 4-5 hours before sleep time. Even at 300-350, look droopy around 3-4 hours before sleep time.

Flowering, going around 700-900, anything higher, light bleach and I do use co2... I really wonder how people can achieve 1500 ppfd!
 
Star Dog

Star Dog

Well-Known Member
I get my plant ready to flower between t5s and 200/250w.
20231225_145034.jpg
To here with 250w It's only now they need the light intensity raised gradually, they'll have filled my space in 7/10 days
(The short ones were only put on Saturday) there should be 6 of the taller one's.
 
N

nxsov180db

Well-Known Member
Have2 said:
I really wonder how people can achieve 1500 ppfd!
Click to expand...
Most I know of in a commercial setting is 1100. I’ve been close to 1500 before and it’s a condition weed just won’t tolerate, you’ll end up with the strangest looking growth you’ve ever seen. This is with a gassed room, vpd and nutes all where they’re supposed to be.
 
Rocket Soul

Rocket Soul

Well-Known Member
One of the grows i follow on icmag did 1200ppfd during 12-12, no bleaching or anything and excellent yields, using 2700k 80 cri but had about 120w of incandescent added to heat the cannopy and for reds reds and far reds. The more light you run the more transpiration you need; not sure you can achieve the kind of transpiration you need for that high intensity just by using ppfd. Also the more light the more temps you need for the plant to keep up. I hope to try something similar soon if i can somehow free up amps in our grow.

CO2: its not an automatic "increase light tolerance" recipe. CO2 will help photosynthesis but also closes the stomata, decreasing the transpiration. If you use co2 you need to redial your climate and maybe even tweak spectrum, especially if using leds.
 
cdgmoney250

cdgmoney250

Well-Known Member
Have2 said:
1000 ppfd in veg... Fuck, that is insane!

I usually go at 300-400 ppfd in veg... Going at 500-600 and they look exhausted 4-5 hours before sleep time. Even at 300-350, look droopy around 3-4 hours before sleep time.

Flowering, going around 700-900, anything higher, light bleach and I do use co2... I really wonder how people can achieve 1500 ppfd!
Click to expand...
The maximum amount of light a plant can use for photosynthesis before photoinhibition sets in, is dependent on many, many variables. This is why you will see different reports from different people.

Mostly, folks will talk about light intensity or environmental conditions being the main factors, which they are. But some other variables that often get considerably less attention are the spectrum of light, total DLI : Maximum PPFD/ total hours of light, and potential nutritional shortcomings.

You will find talk of spectrum quality in a few other current threads, so I won’t go into that here.

If you read back through this thread, you will see many folks suggesting a Max DLI based off [PPFD x Lights-ON Period]. But there is recent research that suggests that plants can photosynthesize under higher PPFD before light stress, so long as maximum DLI is not exceeded. Basically, plants can use higher light intensities for shorter periods of time (before stress) than plants under a static PPFD, given the same amount of “daylight” hours. In theory, you could run plants at at higher Max PPFD if you ramped the intensity up and down to maintain a certain DLI. There are a few studies to support this that I’ve posted before, but not in this thread. They are just a google away though.

Nutrition doesn’t get as much attention in the LED section, but from my studying and research of “optimal” nutritional levels, I believe insufficient total mineral concentrations, as well as antagonistic mineral imbalances are also a limiting factor for the total amount of light a plant can take before stress.

The topic of “optimal nutrition” is outside the scope of this discussion, but how nutrition relates to photosynthesis under varying lighting conditions is within the scope. Below is a link to a research paper discussing the multiple effects and roles of Calcium and its relation to reducing heat/drought/light stress, in addition to many otherbenefits.

www.frontiersin.org

Frontiers | The significance of calcium-sensing receptor in sustaining photosynthesis and ameliorating stress responses in plants

Calcium ions (Ca2+) regulate plant growth and development during exposure to multiple biotic and abiotic stresses as the second signaling messenger in cells....
www.frontiersin.org www.frontiersin.org

I believe that with the optimization of these variables, plants can achieve a higher Total DLI, and also photosynthesize under a higher Max PPFD.
 
Week4@inCharge

Week4@inCharge

Well-Known Member
cdgmoney250 said:
The maximum amount of light a plant can use for photosynthesis before photoinhibition sets in, is dependent on many, many variables. This is why you will see different reports from different people.

Mostly, folks will talk about light intensity or environmental conditions being the main factors, which they are. But some other variables that often get considerably less attention are the spectrum of light, total DLI : Maximum PPFD/ total hours of light, and potential nutritional shortcomings.

You will find talk of spectrum quality in a few other current threads, so I won’t go into that here.

If you read back through this thread, you will see many folks suggesting a Max DLI based off [PPFD x Lights-ON Period]. But there is recent research that suggests that plants can photosynthesize under higher PPFD before light stress, so long as maximum DLI is not exceeded. Basically, plants can use higher light intensities for shorter periods of time (before stress) than plants under a static PPFD, given the same amount of “daylight” hours. In theory, you could run plants at at higher Max PPFD if you ramped the intensity up and down to maintain a certain DLI. There are a few studies to support this that I’ve posted before, but not in this thread. They are just a google away though.

Nutrition doesn’t get as much attention in the LED section, but from my studying and research of “optimal” nutritional levels, I believe insufficient total mineral concentrations, as well as antagonistic mineral imbalances are also a limiting factor for the total amount of light a plant can take before stress.

The topic of “optimal nutrition” is outside the scope of this discussion, but how nutrition relates to photosynthesis under varying lighting conditions is within the scope. Below is a link to a research paper discussing the multiple effects and roles of Calcium and its relation to reducing heat/drought/light stress, in addition to many otherbenefits.

www.frontiersin.org

Frontiers | The significance of calcium-sensing receptor in sustaining photosynthesis and ameliorating stress responses in plants

Calcium ions (Ca2+) regulate plant growth and development during exposure to multiple biotic and abiotic stresses as the second signaling messenger in cells....
www.frontiersin.org www.frontiersin.org

I believe that with the optimization of these variables, plants can achieve a higher Total DLI, and also photosynthesize under a higher Max PPFD.
Click to expand...
Will the reduction of light schedule (during veg) increase internodal spacing?
 
cdgmoney250

cdgmoney250

Well-Known Member
Week4@inCharge said:
Will the reduction of light schedule (during veg) increase internodal spacing?
Click to expand...
I would imagine that light spectrum/intensity would be more of a factor relating to plant morphology, assuming we are taking about a typical 16-18hr daytime period for veg. Longer days will typically need less light intensity, all other factors the same.

Edit: this is why I mentioned varying light intensity throughout the day. In doing this, plants can be blasted with higher levels of light during peak hours (midday), so long as overall DLI isn’t exceeded.
 
madvillian420

madvillian420

Well-Known Member
Have2 said:
1000 ppfd in veg... Fuck, that is insane!

I usually go at 300-400 ppfd in veg... Going at 500-600 and they look exhausted 4-5 hours before sleep time. Even at 300-350, look droopy around 3-4 hours before sleep time.

Flowering, going around 700-900, anything higher, light bleach and I do use co2... I really wonder how people can achieve 1500 ppfd!
Click to expand...
its certainly strain and probably even phenotype dependent. Some of the plants ive grown absolutely flourished at 1100 ppfd and some couldnt handle it. I suspect overall plant health might play a role too. If theres some deficiency or something of the sort things are more likely to go downhill if you blast em with extra lumens.
 
Have2

Have2

Well-Known Member
cdgmoney250 said:
The maximum amount of light a plant can use for photosynthesis before photoinhibition sets in, is dependent on many, many variables. This is why you will see different reports from different people.

Mostly, folks will talk about light intensity or environmental conditions being the main factors, which they are. But some other variables that often get considerably less attention are the spectrum of light, total DLI : Maximum PPFD/ total hours of light, and potential nutritional shortcomings.

You will find talk of spectrum quality in a few other current threads, so I won’t go into that here.

If you read back through this thread, you will see many folks suggesting a Max DLI based off [PPFD x Lights-ON Period]. But there is recent research that suggests that plants can photosynthesize under higher PPFD before light stress, so long as maximum DLI is not exceeded. Basically, plants can use higher light intensities for shorter periods of time (before stress) than plants under a static PPFD, given the same amount of “daylight” hours. In theory, you could run plants at at higher Max PPFD if you ramped the intensity up and down to maintain a certain DLI. There are a few studies to support this that I’ve posted before, but not in this thread. They are just a google away though.

Nutrition doesn’t get as much attention in the LED section, but from my studying and research of “optimal” nutritional levels, I believe insufficient total mineral concentrations, as well as antagonistic mineral imbalances are also a limiting factor for the total amount of light a plant can take before stress.

The topic of “optimal nutrition” is outside the scope of this discussion, but how nutrition relates to photosynthesis under varying lighting conditions is within the scope. Below is a link to a research paper discussing the multiple effects and roles of Calcium and its relation to reducing heat/drought/light stress, in addition to many otherbenefits.

www.frontiersin.org

Frontiers | The significance of calcium-sensing receptor in sustaining photosynthesis and ameliorating stress responses in plants

Calcium ions (Ca2+) regulate plant growth and development during exposure to multiple biotic and abiotic stresses as the second signaling messenger in cells....
www.frontiersin.org www.frontiersin.org

I believe that with the optimization of these variables, plants can achieve a higher Total DLI, and also photosynthesize under a higher Max PPFD.
Click to expand...
Exactly, but what's the point of let's say, 1500 ppfd if you have a maximum DLI the plant can take... Just make no sense to go that route!
As far as nutrient, i'm all in on this. Just when you put your clones under LED, less transpiration and you have to raise nutrient's ppm, once they are established, you kinda keep the same ppm, they can get higher dose but since transpiration is higher, less concentration is needed.
 
Have2

Have2

Well-Known Member
madvillian420 said:
its certainly strain and probably even phenotype dependent. Some of the plants ive grown absolutely flourished at 1100 ppfd and some couldnt handle it. I suspect overall plant health might play a role too. If theres some deficiency or something of the sort things are more likely to go downhill if you blast em with extra lumens.
Click to expand...
I have a strain that, in veg, 200 ppfd is sufficient, else all weird things happens to the leaves and once in flowering, you can hit her with 900 ppfd and it's fine while others, 300-350 in veg and same maximum in flowering, 900.

So seeing that much differences between strains/phenotypes, it's hard to really be sure of any studies out there. It gives a ballpark though!
 
cdgmoney250

cdgmoney250

Well-Known Member
Have2 said:
Exactly, but what's the point of let's say, 1500 ppfd if you have a maximum DLI the plant can take... Just make no sense to go that route!
Click to expand...
There is strong supporting research that total whole plant photosynthesis increases and plants have higher yields when grown under higher Max PPFD, so long as photosynthesis is not inhibited. So more yield out of the same grow space/same life cycle.
 
madvillian420

madvillian420

Well-Known Member
cdgmoney250 said:
There is strong supporting research that total whole plant photosynthesis increases and plants have higher yields when grown under higher Max PPFD, so long as photosynthesis is not inhibited. So more yield out of the same grow space/same life cycle.
Click to expand...
i grew cuts of the same strains in the same room twice. and on one grow i lowered the light closer than ever, from about 900ppfd to 1100-1200 and the buds got massive. Yield on the colas in the middle/hottest zone were very obviously much larger than the rest. Thats all the research and studies i need right there lol.

Ive had people tell me that my plants would die or get severely stressed from that much light on this very forum because they cited some study that said so. Do your own study lol fuck what ya heard.
 
Have2

Have2

Well-Known Member
madvillian420 said:
i grew cuts of the same strains in the same room twice. and on one grow i lowered the light closer than ever, from about 900ppfd to 1100-1200 and the buds got massive. Yield on the colas in the middle/hottest zone were very obviously much larger than the rest. Thats all the research and studies i need right there lol.

Ive had people tell me that my plants would die or get severely stressed from that much light on this very forum because they cited some study that said so. Do your own study lol fuck what ya heard.
Click to expand...
Was the yield the same? I mean, high ppfd in the middle may lower the edges, average ppfd.
 
Week4@inCharge

Week4@inCharge

Well-Known Member
madvillian420 said:
i grew cuts of the same strains in the same room twice. and on one grow i lowered the light closer than ever, from about 900ppfd to 1100-1200 and the buds got massive. Yield on the colas in the middle/hottest zone were very obviously much larger than the rest. Thats all the research and studies i need right there lol.

Ive had people tell me that my plants would die or get severely stressed from that much light on this very forum because they cited some study that said so. Do your own study lol fuck what ya heard.
Click to expand...
Opposite for me, plant under 1050 ppfd smaller buds than the one under 800 ppfd.
 
madvillian420

madvillian420

Well-Known Member
Have2 said:
Was the yield the same? I mean, high ppfd in the middle may lower the edges, average ppfd.
Click to expand...
Im using a 500w light in a 32"x32" space so the edges are almost always getting adequate light, never less than 5-600 ppfd in any spot on full blast.

But thats a totally good and valid point in most cases
 
Rocket Soul

Rocket Soul

Well-Known Member
madvillian420 said:
Im using a 500w light in a 32"x32" space so the edges are almost always getting adequate light, never less than 5-600 ppfd in any spot on full blast.

But thats a totally good and valid point in most cases
Click to expand...
Over 50w per squarefoot and only 5-600 ppfd as lowest measurement? What are you growing with? Whats your highest measurement? Open space or tent? Sounds low tbh for that wattage
 
N

nxsov180db

Well-Known Member
Rocket Soul said:
Over 50w per squarefoot and only 5-600 ppfd as lowest measurement? What are you growing with? Whats your highest measurement? Open space or tent? Sounds low tbh for that wattage
Click to expand...
Maybe he means 500w equivalent? Like the way those cheaper light company’s market their lights? Or he’s got the light 6 feet away lol
 
madvillian420

madvillian420

Well-Known Member
Rocket Soul said:
Over 50w per squarefoot and only 5-600 ppfd as lowest measurement? What are you growing with? Whats your highest measurement? Open space or tent? Sounds low tbh for that wattage
Click to expand...
closet grow, and that measurement is a corner, farthest from the light. BudgetLED 500. Id have to check on distance but id guess no higher than 16-18" They went out of business but its basically an HLG clone.
 
L

Lou66

Well-Known Member
Have2 said:
So seeing that much differences between strains/phenotypes, it's hard to really be sure of any studies out there. It gives a ballpark though!
Click to expand...
That is why one study is never conclusive. The same way that a single measurement has an error a whole study can have an error. Either by chance, bias of the methods used or an important factor that was not controlled (by mistake or deliberately).
But once you have 30 studies with similiar but varying methods you can become confident and generalise.
Science is slow.

But your point is valid. Every cultivar has to be optimized and in other crops there are much fewer cultivars with commercial value. But with cannabis everyone wants the latest strains and commercial production is hampered.
 
Have2

Have2

Well-Known Member
Lou66 said:
That is why one study is never conclusive. The same way that a single measurement has an error a whole study can have an error. Either by chance, bias of the methods used or an important factor that was not controlled (by mistake or deliberately).
But once you have 30 studies with similiar but varying methods you can become confident and generalise.
Science is slow.

But your point is valid. Every cultivar has to be optimized and in other crops there are much fewer cultivars with commercial value. But with cannabis everyone wants the latest strains and commercial production is hampered.
Click to expand...
It would be nice if they could use CRISPR to remove the herm trait in all those "latest strains" :P
 
Last edited:
You must log in or register to reply here.
Top