Growing with added UVA and Far Red

[ControlLED]

Thoughts On Growing with added UVA and Far Red?
 

Photosynthetic Active Radiation or PAR refers to the spectrum of electromagnetic radiation that plants can use. Plants use this light energy to drive photosynthesis, grow and reproduce. The spectrum is measured in nanometres (nm) and for many years it was agreed that the range of visible light (PAR) sits between 400nm and 700nm.

At the low end of the PAR range is blue light and at the upper end is red light.
 

Recent plant research states that expanding the spectrum of light outside of the “traditional” PAR range has significant effects on plant behaviour and that the actual usable range is 380nm to 780nm.
 

The Dio-Tech UVA/Far Red Light Bars does just that. It extends the spectrum to include not only visible light, but also UVA and Far Red, for optimal plant performance.
 

Electromagnetic radiation with a wavelength between 315nm and 400nm is classed as UVA. This wavelength induces a stress response within the plants, much as it does in humans, to develop compounds that will protect its cells from being damaged by prolonged exposure.

Receiving UVA radiation stimulates the plants natural defences and encourages it to develop thicker, waxier leaves. This helps protect the plant against biotic stress factors, like pests, fungal and bacterial pathogens. Research also suggests that UVA deters certain species of sucking insects.

Most importantly, exposure to UVA during the flowering period stimulates the production of resin, terpene and flavonoid compounds, and increases biomass.
 

NOTE: We do not use UVB emitting diodes in our fixtures as this wavelength of light can be harmful to both plants and humans unless dosed for short periods of time. UVA can be on all the way during your flowering cycle while your lights are on – it is not restricted to 15 minutes per day, unlike UVB.

Far red or FR is found at the opposite end of the PAR spectrum to UVA, it sits between 700nm and 780nm. It was widely believed that FR on its own stimulated little photosynthetic activity within the plant and that it was not included in the PAR range. This phenomenon was known as “Far Red Drop” as the rate of photosynthesis significantly drops beyond 700nm.
 

However, later research by Robert Emerson found that when FR was combined with deep red wavelengths of around 680nm it becomes photosynthetically active and increases the photosynthetic rate beyond what is usually achievable below 700nm. This phenomenon is known as The Emerson Effect.
 

This “stacking” of usable light significantly increases biomass and flower production.
 

FR penetrates the leaf canopy more deeply than blue, green or red, so much so that exposure to FR triggers a shade aversion response stimulating stem elongation and flower development in plants as they try to outgrow and compete against the plants that are shading them. It is for this reason that we recommend only using the UVA/FR Light Bars during flowering.

I look forward to hearing everyones thoughts on adding UVA and Far Red!

- Control LED Team

 

[Saddam]

The trouble is UVA is a complete waste of time and money, also damages plants and humans, just look at folks who use a sunbed too much.      

 UVB is what increases trichome production, 280-315nm.   

[MidgeSmith]

I have to say, having used UVB for 3 hours a day on my last grow, it didn't seem to damage the plants at all and did seem to increase the strength over the time before, but that isn't lab, just obvs. Not sure the theory matches my findings, but hard to tell sometimes...

It was only a gentle light 60W and at least 3ft above the plants.

Edited October 6, 2022 by MidgeSmith

[Shumroom]

I don't use FR but I do have a couple of Grow The Jungle 90W Mantis UV units,

They produce UVB and I use them for 4 hours per day from the 4th week of 12/12  

 

I think they improve the terps similar to when I first discovered CDM instead of/combined with HPS  

 

Atb

 

 

 

[DeltaMelter]

Used the SolarCure UVB and while it doesn't make the herb stronger as such it makes it "terpier" and the oil profiles are different vs without. It also keeps the internode spacing a bit shorter too, especially using it in short bursts during early flower.

[Shumroom]

I might have to give it a go earlier than usual at lower doses

 

Atb 

 

 

 

[RUFUS HOUND]

interesting info

 

I have 2 chinese 85W boards ( I know I know but its what I have ) each board has a single chip of UV (380nm) and one of infrared (670nm)

It has a veg /bloom switch but that just turns off the red(660 and 760nm) leds but the UV stays on permanantly.

now if Ive understood it correctly, The UV (which I believe is UVA) is damaging during veg and of benifit only in flower - so I guess I should cover them up untill flowering?

[Shumroom]

@RUFUS HOUND I wouldn't worry about maybe 3W or less of UVA.

 

My Highlight 220's also mimic UV using a coating on some of the LEDs. 

 

I use one Highlight 220 in my nursery tent as well as 2 of them in my Secret Jardin dr150w(veg and bloom). 

 

Atb 

 

 

 

 

[v12xjs]

I salute your efforts to help but I don't think my grows would benefit from such a light.

 

Red and far red are really important signallers for plants and we simply don't use them correctly.
Using far red all the time with lights on will only produce the shade avoidance response you mentioned. This of course will divert resources into getting taller when we want the plant to be concentrating on flowering.

 

A much better use of red light IMHO is to put phytochrome into the correct form for the time of day. ie inactive at night and active in the day.
It's a simple thing really and phytochrome is what makes plants flower. And used incorrectly it can also inhibit flowering.

 

Just flood the plant a little before lights on with red light and it will wake up and be ready to photosynthesize when the lights come on.
At the end of the day if we flood it with far red then that turns the phytochrome to the inactive form and all the night processes begin immediately.

 

Without those signals it takes plants about 30 minutes to work out there's no light through other means and again in the morning it takes another 30 mins to work out the lights are on.

So just talking to the plant and telling them we are turning the lights on and off will give them up to 60 minutes extra growth every day.

 

I'd be much more interested if you made a light like that.

[MidgeSmith]

Hey @v12xjs I hadn't heard of putting them on in the morning too.  Very interesting!

Could you help with 3 quick quest questions? I would very much appreciate it.

1) Is the time the far-reds are on, part of the 18 hours (or 12 hours for that matter), or are they in addition?

2) How long would you recommend for each of the pre-lights-on and post-lights-off periods?

3) Were you meaning that it'd be good to have a light that gave pre and post reds automatically (switchable to on-off-auto I guess)?

 

Cheers for the info

[RUFUS HOUND]

does it really mater what time of day it is - I doubt that the plant (indoors) know what fooking time it is, it reacts to light  you give it

 

[RUFUS HOUND]

5 hours ago, Shumroom said:

@RUFUS HOUND I wouldn't worry about maybe 3W or less of UVA.

 

My Highlight 220's also mimic UV using a coating on some of the LEDs. 

 

I use one Highlight 220 in my nursery tent as well as 2 of them in my Secret Jardin dr150w(veg and bloom).

Fair enough, I didnt think that one chip would make a vast amount of difference but Ive put some blutac on them just to see

[Shumroom]

The best way to know is to give it a go

 

 

I didn't mean for that to rhyme btw

 

Atb 

Edit: Or perhaps subconsciously I'm a poet, 

nah I doubt it. 

 

 

Edited October 7, 2022 by Shumroom
Eta

[RUFUS HOUND]

@Shumroom and you dont know it !

[v12xjs]

Hi @MidgeSmith
A 5-10 min burst pre and post lights on is all that's needed.
It's the continued use of far red during the day that triggers the shade response so it's counter productive to keep that on with the main light.
Would be ideal to get both from a single unit but of course there are numerous challenges to overcome in order to do that. In my head it would be 10 min flash of LED bank 1, off for 12/18 switchable, 10 min flash of LED bank 2.