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do chili plants benefit from UV light?

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#1 MarcV


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Posted 06 November 2016 - 01:18 PM

I'm growing my seedling chili plants under a couple of sylvania grolux lamps. I was wondering if replacing one of the grolux lamps by a reptistar lamp would be beneficial. The reptistar produces light with a 6500 Kelvin color temperature but also produces UVA and a bit of UVB light. Would this be a good idea?

...but I might be wrong...

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#2 Slug


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Posted 16 January 2017 - 01:45 PM

In a nutshell, even though you probably already decided on this.  "Yes."  I realize this post is months old, but it looks like you never got a response and the question deserves one.  The answer is "yes, all plants benefit from UV light, but perhaps not in the way you might think".  Plants make use of both UV and IR, but do not use either for photosynthesis and do not need either to grow healthy.  That stated...


UV light causes damage to plants and fruits just like it does to humans and materials.  In high doses, you torch the plant.  In reasonable doses, the plants respond to this damage by manufacturing protective chemicals they do not need or have much of under CFL, Halide, etc.  (Think anti-oxidents.)  I have run personal experiments in the past and you can notice a visible difference in the color and growth patterns of plants that you expose to UV / IR versus the ones you do not.  There have been several university studies that show plants/fruits exposed to UV contain a greater amount of up to 14 different things that make them smell and taste good to us.  Here's one Dutch study I recall that was fruit-specific:




Ever notice how you can tell when it is "hothouse tomato season" at the grocery store?  Greenhouses are built to filter out UV to protect the equipment in them.  If you put the UV back artificially, studies suggest you will also get back some of the color and flavor you lost.  This has been my personal experience when fooling around with highly customizable LEDs versus other types of lighting.


There's also a benefit to IR.  If you're running an HPS setup, you already get way more than you want of this (heat), but with other indoor lighting setups (especially LED) it can be mostly absent.  Various studies show that IR exposure causes better node spread and potentially healthier plants.  Can help them grow less leggy, sturdier, and more straight.




The easiest/cheapest way I know to supply the low doses of UV and IR that you might want remains LED, for now.  Please note that it doesn't take much at all to yield the beneficial effects you might be chasing.  The lamp you mention would work, but you could quite literally keep the exact setup you have right now and just make a DIY LED fixture with a couple of each type of LED (UV and IR) per 2-3 square feet of grow space.  See Peter's grow tent thread for a shot of my seedling tent.  That particular fixture is driving the individual lights @ 5W and using only 2 LEDs each of UV / IR out of 60 total.  That's not much at all, but it helps.  If I had grown some seedlings outside the box this year, I could show you the initial node spread comparisons.  It can be a very noticeable difference under IR for certain plants.  Here's a list of more scientific studies than you probably ever wanted on plants and specifically LED lighting:




But as LeVar Burton always said, "you don't have to take my word for it".  Go science some shit.  Cheers!

#3 MarcV


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Posted 16 January 2017 - 02:43 PM

Wow thanks for the very extensive Reply! :)

...but I might be wrong...

#4 Powelly



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Posted 27 January 2017 - 09:01 PM

Infra-red is more important

It's a non-issue anyway really, most lighting will do the trick. 4000-6000 Kelvin LED or Fluro

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