Dear all,
I am very new on this and I would like to apologise if I am asking silly questions.
Breeding has included several traits such as flowering time, hardness to pest, aroma, yeld,etc…
But I was thinking if would be possible to consider to breed for light. I will try to explain better.
Never happend to you that you spot a strain that need less PAR light to fully mature or a specif strain that for example under LED harvest better than under other light ( or better mote powerful lights)?
Strains for example created only for indoor which under too much light ( if light can be too much) are performing less.
Ruderalis I am not sure if could count.
I read a lot about outdoor growing where the plant although receiving 8-12 hours of full direct sun light is not processing constantly all the light but arrive a point where the photosynthesis proceed is saturated and maybe the plant with 8 hours perform as well as with 12 hours.
Again apologies if I am questioning a silly topic.
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This is an interesting question. There is research that suggests cannabis has a tolerance for high light levels. I haven’t looked at light saturation points in Cannabis for a bit, but here is a screenshot with some citations that might be worth checking out
To me, this would suggest that the limit of photosynthesis isn’t light but CO2 concentrations. This makes me think that improvements to PS need to focus on an enzyme, RuBisCO.
Ive never heard of people breeding for it, but they for sure exist! Back in the old Norcal days, they had a lot of strains that could grow in full shade to hide from the helis. Deep Chunk seems to be the popular one thats still around. The real downside is theyre usually super low potency and yield. But it’s forsure a niche that isn’t filled.
Ive also ran autos in full shade that did a lot better than full sun. Which makes sense with the ruderalis genetics. When I ran big dep greenies, I also forsure found a lot of the purps/gelatos and bs did really well later in the year when the DLI was a lot less and temps were cooler. So theres some range in there for sure.
Many thanks all for the amazing link and comments.
Sliglty OFF topic, but I am reading more and more about growers who for examples are considering ( some already using) different schedule light while growing. For example 6/6. Which is still 12 hours/day, but the theory beyond is that after the 6 hours of light the plant is saturated and giving her/him 6 hours rest and other 6 of light optimise the grow cycle having plants absorbing 100% of required light.
Of course never tested myself neither I had yet chance to follow a grow diary with these parameters.
Another thought is related to the idea that natural light from September is reducing considerably and in October is far from the 12hours we are use to. nevertheless is exactly during these months that cannabis ripen.
Someone including suggesting that exactly because the plant start feeling the reduction of light, the lower temperature, etc some strains develop more flowers in order to try to improve pollination chances.
Hopefully some cleaver grower will test it some day:)
There’s a paper out looking at different light intervals for cannabis flowering, I’ll try and find it when I get home and link it.
Essentially, reducing hours of light to mimic natural daylight hours reduces overall yield and potency. The plant is still doing photosynthesis in flower so reductions in light = reductions in PS = reductions in yield and cannabinoids.
In veg, that might be a different story. Ive seen some studies that suggest that reduced daylight hours during veg results in an increased growth rate. These were done outdoors so its hard to separate the effect of the plant is larger and may be able to collect more resources vs the circadian response of increase growth rate
I agree with it, or at least is what logic seems to indicate.
Regarding outdoor and hours of light I was thinking about those sativa that take 14 weeks to flower ending on November for example. During this month’s plants don’t take more than 8 hours of fully light, probably 6 if we consider that between 7 and 9am the sun is not so strong and at 4pm is already night.
Someone could comment that actually sativas of this kind harvest less than indica plants and this bring us back to your comment.
I would be very curious to see these lights interval…more keen to test them ( if i had space,time,money,etc which is not my case unfortunately).
People certainly do selection based on how a given plant performs in their available conditions, which can be effectively breeding for the available light source.
This is true but that selection is also muddied by various plant physiological factors. Plants may perform better because of soil chemical or physical properties that are better for a given genotype, could grow better or worse based on inherent ability to scrounge nutrients and compete with others, or it could be due to temperatures. The plant may also do better because the genotype is able to produce detoxifying molecules that counter reactive oxygen species generated, however these are broadly used by plants to detoxify harmful chemicals or even bacteria.
Ultimately, selection for light reaction is likely really difficult to do. Mostly because of how important light is to plant survival and how integral it is for for their reproduction. I also think the reason why you see so much magnesium deficiencies is related to light intensity, so selecting for plants that better or more efficiently accumulate and use magnesium might be an easier way.
Here’s a link for altering flowering light intervals, they had some start at 15 and 14 hours of light (9 and 10 hours of dark is more correct though) but that is almost definitely genotype dependent
Nasa has done a few studies on light saturation point of various crops, cannabis being one of them. From what I recall, without additional CO2, roughly 1050 ppfd was where they saw growth cap. Including CO2, they saw it raise to about 1350.
When it comes to breeding for it, I wouldn’t really think it’d be all that difficult if you’re already growing numbers. If things bleach under high intensity, don’t breed with it. Obviously that’s simplifying things quite a bit, but don’t let the textbooks stand in your way of starting something. Just try it
And I’m fairly certain there are lots of folks who do incremental stuff…starting at say 15 hours and working down to 11 hours of light by the end of harvests. I haven’t done it myself but have read and heard positive things. Sorry I can’t be more help. Have fun
That’s very interesting.
It is true that CO2 concentration and levels are influencing PAR or maybe viceversa.
Several manufacturers of LED already indicate that for example ( refering to AC infinity IONFRAME) a 300w works for let say 4X2 but with CO2 implementation the lights could/should be increased up to…600W-800W for example.
The CO2 is needed for the enzyme that runs PS, RuBisCO. The C is for carbon but its not a very selective enzyme so oxygen can also be incorporated, when that happens its called photorespiration and the plant suffers. The C is used for building sugars, the O costs the plant energy.
When you increase the CO2 at high light levels you are lessening the chance of PR and helping with PS. The extra light generates more usable energy but the plant needs more CO2, mostly because of atmospheric CO2 levels naturally.
I’m definitely not trying to discourage you! But I do know selecting for light can be really complicated and don’t want to see anyone invest time and resources into something that doesn’t work or something that fails.
Many thanks,
I see your point and I agree about it
Nevertheless I can’t stop thinking how cool could be to broken some physic rules and have a plant that harvest amazing with 200-300umol/J
I found few threads around the web and one user was mentioning this breeder ( The only breeder that actually bred for low light successful strains was Vic High of BCGA)…this 10years ago. Anyone know him/her?
But it is true the sun is approximately 2,000 umol? ( 108,000 lux)?
Because a 1000w hps is between 120,000 and 145,000 ( I don’t fully understand this).
Also when refering to lighting requirements for indoor growing I noticed several info regarding 30-40W for square feet.
Indepently if this info is correct or not, the idea that there is a variable ( i.e 10w sqf difference) i still consider quite interesting assuming some specific strains will do good at 30 while others at 40.
The other aspect I was thinking about is regarding for example the breeding work done by Netherland regarding outdoor strains. It is well know several people is looking for reduced flowering time, but it is also true that some genetic where developed for climates like Netherland or general North Europe where the ammountnof light is relatively reduced.
In Netherland there is not a full summer with full light and actually is more “partially or fully cloud” summer.
How much light intensity actually some of these strains need to fully mature there outdoor? ( 1,000-1,500umol? I don’t know)
