I posted this on one of the biggest international forums 2 years ago.
Not one member there responded …LOL
We will try it here.
Open to all discussions on this topic.
I read yellow light (580–600nm) light appears to inhibit lettuce growth.
Does anyone know if yellow light has the same effect on cannabis?
[Dougher and Bugbee (2001) concluded that an increased proportion of ‘yellow’ light (λ580–600 nm) was responsible for a decrease in lettuce yield, perhaps due to suppression of chloroplast or chlorophyll formation, when comparing growth under HPS and MH lamps.
I agree, but I like LED now.
By a technicality, a MH will grow better weed than HPS.
More secondary metabolites, THC, ect.
Usually less mass, with added leaf.
I wonder if there is a chart that shows the amount of yellow in each of those?
First of all, HPS is not yellow light, it’s red/orange, but mostly red. That’s why it’s used for flowering.
MH is blue light and promotes growth.
Yellow, orange or white are all the wrong spectrum for proper plant photosynthesis and can’t create carbohydrates for the plant to use, therefore, they offer very little value to growing plants and are absorbed by the plant in very small quantities, like green light is.
The violet-blue spectrum promotes chlorophyll production, photosynthesis and plant growth.
My statement holds true.
Check the statement again, please.
It speaks of a yellow to red ratio.
I am pretty darn sure HPS has some yellow.
Don’t ignore the green light
Blue is not for veg and red is not for flowering - that’s flawed logic based upon common misunderstandings about sunlight.
Cannabis doesn’t use light (in terms of spectral quality) much different than other higher C3 plants.
The HPS is good in terms of photosynthesis, in fact, it’s YPF/PPF ratio is very high (which means per total light output there’s more photons that are more effective at driving photosynthesis than for example, an MH).
However, your el’ cheapo HPS lacks important wavebands for some photomorphogenesis.
For example, it’s likely there is more yellow light from your HPS than is good for the plants, as well as more far-red light than is helpful (leads to plant stretch). Around 10% blue light (as total radiant PPF) is a good minimum goal for plant growth lighting.
They are more receptive to the blue spectrums…yellow lights make them stretch. If you notice alot of the LEDs are ultra Violet…you see the purple glow form the lights in the city.
In nature the light gets yellower in the fall, because the sunlight has to travel through more of the atmosphere, corresponding to the flower phase of growth.
It’s really a coincidence that this is 12/12.
When outdoor growing are the benefits of supplementing extra light exposure of those spectrums at the proper time noticeable enough to keep lights on hand?
I must say, I do not know anyone that is growing outdoors that is using supplemental lighting.
If you are talking about greenhouse growing, I have no experience with that.
Now if you are asking is supplemental lighting helpful on cloudy days I would say yes.
I never used any type of extra lighting on an outdoor grow. The sunlight was plenty strong.
I have seen outdoor plants, back in the 70’s/80’s mostly, that were planted under/near various types of HID lights, mercury vapor, metal halide, sodium vapor, ect., that came on at dusk and off at dawn.
Some of those plants turned into monsters, although I don’t remember how well they yielded… that, in itself, could be the answer, however, I’m sure that some had to yield well depending on what light spectrum they were influenced by during the nighttime hours.
We didn’t take many pictures of cannabis plants back then, if you got caught cultivating cannabis, your pictures were proof and helped convict you.
I understand that last part a lot. I have a lot of older cousins, uncles, and family friends who spent time in jail because of green harvest busts! They’d just fly a chopper right into your yard and destroy everything you had and take you in from what I understand. Thank you though for your input, I was asking for these winter months because of how short light hours can be. I was talking to a friend and they said to just have a cover tent with lights in it or get some pole lights and set them over them around 6.
Ah, I understand now… so you’re just looking to prolong the light exposure your plant receives.
Yeah, what your friend suggested is very doable and an easy fix for the thrifty grower on a budget. Sometimes you gotta do whatever is necessary to get through. As long as the end product is to your approval and does what it should, that’s success.
So after a review of Dr. Bugbee’s research on lettuce can we assume that increased proportion of ‘yellow’ light (λ580–600 nm) can be responsible for decreased yield in cannabis.
Why should we believe this may be true?
It is possible that an increased proportion of yellow light in the spectrum could have an impact on cannabis yield because yellow light is not as effective at supporting photosynthesis as blue and red light.
Photosynthesis is the process by which plants use light energy to convert carbon dioxide and water into glucose and oxygen.
Different wavelengths of light are absorbed by different pigments in the plant, with blue and red light being absorbed by chlorophyll, the primary pigment responsible for photosynthesis.
Yellow light is absorbed less efficiently by chlorophyll compared to blue and red light, so it is not as effective at supporting photosynthesis.
I would seem yellow light stimulates the plant’s defense mechanisms, causing it to produce more terpenes as a protective response.
Anytime you put energy toward defense you may inhibit growth in favor of defense.
So it seems yellow light can inhibit growth of cannabis in favor of defense.
…LOL
