Low Pressure Sodium (LPS) streetlights and flowering...
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FresnoFarmer
Well-Known Member
How far away?
WAWill
Member
I'd go with the old adage - hold your hand at arm's length in front of your face in that light after a few minutes in it to let your eyes adjust. If you can see the hand, there's too much light.
That said, plant circadian rhythms are believed to be regulated (solely?, I don't know) by cryptochromes - a class of proteins which absorb visible light almost entirely in the blue. Below about it looks to be 525nm, it appears they're pretty much unresponsive. So, if that were the end of the story, I guess you'd be good.
Of course, chlorophyll A&B too are almost entirely unresponsive at the 590nm* of the LPS. Then again, the anthocyanins (blue/purple plant pigments) are. They're not involved in photosynthesis, but I'm reading that they do serve protective functions, so it seems their excitation is tied to at least some processes in the plant metabolism.
Sorry I can't be more conclusive, but I think I can at least say that things could be a hell of a lot worse with just about any other kind of light in place of those LPS bulbs.
* I want to give you positives, but this is also why I open w/ the old adage - from a little hopeful research, your situation looks like it might work. And yes, there is FAR more energy packed into that 590 nm peak than anywhere else for lps. However, if you see, rather than one of those response graphs which are most of what Google spits back, just a real live spectrogram of one of these bulbs (like, made from a CD[used as diffraction grating], razor blades, and paper) with your naked eye, there is a palpable bit of light in two orange/red wavelengths and even a bit at two blue-green/cyan peaks. So, if there's any way of mitigating the exposure to your plants, it's probably worth doing. Still, again, if you have to live with it, could be worse.
That said, plant circadian rhythms are believed to be regulated (solely?, I don't know) by cryptochromes - a class of proteins which absorb visible light almost entirely in the blue. Below about it looks to be 525nm, it appears they're pretty much unresponsive. So, if that were the end of the story, I guess you'd be good.
Of course, chlorophyll A&B too are almost entirely unresponsive at the 590nm* of the LPS. Then again, the anthocyanins (blue/purple plant pigments) are. They're not involved in photosynthesis, but I'm reading that they do serve protective functions, so it seems their excitation is tied to at least some processes in the plant metabolism.
Sorry I can't be more conclusive, but I think I can at least say that things could be a hell of a lot worse with just about any other kind of light in place of those LPS bulbs.
* I want to give you positives, but this is also why I open w/ the old adage - from a little hopeful research, your situation looks like it might work. And yes, there is FAR more energy packed into that 590 nm peak than anywhere else for lps. However, if you see, rather than one of those response graphs which are most of what Google spits back, just a real live spectrogram of one of these bulbs (like, made from a CD[used as diffraction grating], razor blades, and paper) with your naked eye, there is a palpable bit of light in two orange/red wavelengths and even a bit at two blue-green/cyan peaks. So, if there's any way of mitigating the exposure to your plants, it's probably worth doing. Still, again, if you have to live with it, could be worse.
indcolts77
Active Member
Some anecdotal evidence for you so take with a grain of salt buuut....I grew a Master Kush clone in my backyard that got hit with a street light about 40 yds away every night since I put it out and she gave some of the better bud in my harvest....not saying it helped at all, only that consistency is key...if she's hit with it from the get go you should be fine, especially if its indirect...fuck with her light schedule too much and you MIGHT have problems with herms
WAWill
Member
Short answer
There is no wavelength of moonlight. The moon is mostly just reflecting light from the sun. There is presumably some effect from the moon's better/worse absorption at different light frequencies, but I don't believe this is a major effect. The sun emits light at all possible* visible wavelengths.
A little more info
The sun is about as close to an natural blackbody you're going to get. A blackbody is an object which, when heated, emits photons/light across the visible spectrum. So, when you see one of those spectrograph images I was talking about of the sun OR moon, it pretty much looks like a contiguous rainbow. Whereas, the type of streetlamp described by the OP looks like one really powerful swath of orange/yellow right in the same place as the yellow in the rainbow of the sun (with four tiny fluffs of color in other places which also correspond to points on the rainbow).
This is actually a key difference - blackbody radiation versus emission/absorption spectra. When we heat up an elemental gas, like in CFLs, T5s, LPS lamps, etc., it can ONLY produce light at very particular frequencies*, so we see little peaks in light at just those frequencies. This also works in reverse. For example, if you make a REALLY good spectrograph, you'll see that the rainbow produced from our Sun has weird little gaps in it. If you then heat up different gasses which exist in between our sun and us (largely the atmosphere) and place the little peaks of light they produce over those gaps in the Sun, you'd see that they match up.
Why do we as growers give a damn?
Well, to me the best reason may become efficiency. We spend a sheitload on power. Light IS energy. We don't want to produce it at anything other than the frequencies at which our plants utilize and react to it, otherwise we're just making waste. This is, in future, the hope for the LED technologies I'm still no where near adopting - the ability to produce ONLY useful frequencies, and get way more bang for your buck. Aside from expense of new and often misapplied technology though, a big problem with this is that we don't actually know all of the frequencies we should be producing. Yes, we have a pretty good understanding of the absorption curve for chlorophyll A & B, but what of the anthocyanins? What of they cryptochromes? What are the compounds we're now finding which react to UVA&B? Basically, the chisel's not efficient enough yet - Personally, I'm sticking with the sledge for now.
Your other question
I have no idea what a louvred gable vent is, but the 'see your hand after a minute in the room' rule DEFINITELY applies to this kind of light.
* atoms emit light as their electrons drop from higher to lower energy levels. the frequency of that light is determined by the number of shelves dropped by the electron. This is a key part of how we understand blackbody radiation - if these things emit light over the entirety of some range of frequencies, then, if there are no limits to frequency, ANY range of blackbody radiation would mean an INFINITE amount of energy, no matter how little was being emitted at a given frequency. A bit like zeno's paradox - no matter how little energy there is at frequency 1 and frequency 3, we can always look in between them at frequency 2, or between those at f1.5, or those at f1.25, etc. If the energy is roughly constant across the range in this case, it is infinite in output. So, thankfully, photons work more like whole numbers - there just aren't any between 1 & 2. And there just aren't any light frequencies between a one-shelf-jump and a two-shelf-jump. Aaaaaand all of that just gets rid of any apparent conflict between the limited total energy the sun puts out, and the whole 'all wavelengths' thing.