# Lighting question



## kiwi (May 13, 2017)

As we are now into winter I have brought my roths and sandies inside. I have got several LED bulbs that read 18W ES 6500K 'Cool Daylight". Could the lighting experts out there please tell me if these will suffice for winter lighting for these plants?
Thanks in advance


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## troy (May 14, 2017)

Yes, they will work good, I use 6500 k daylight 32 watt t8s from home depot and I bloom all my stuff


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## naoki (May 14, 2017)

It wouldn't be my choice, but I'm sure it works if you give sufficient amount of light (i.e., close enough).


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## kiwi (May 14, 2017)

Thanks. What would be the best LED for indoors then?


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## naoki (May 14, 2017)

Kiwi, "best" is not easy, and depends on what criteria you use. For example, from efficiency, most light bulbs are pretty far from the best. If money (efficiency) doesn't matter, orchids would grow with sufficient light. So the light fixture which gives most light (without burning plant) could be the best.

There aren't so many data examining the effects of light spectra on orchid physiology although there is no doubt that the physiology is influenced by the spectra. So we can't quite say which color is best. But from semi-educated guess (borrowed from other types of plants), 6500K LED seems to have excessive blue. I use 3000-5000K. To be honest, I don't see too much difference in orchid growth between 3000K and 5000K. 6500K probably works ok, too.

So I wouldn't worry too much about the color, and you can try to adjust the height to give the sufficient amount of light.

I personally prefer 4000K or 3000K since I'm trying to be more cautious about blue light. It's been shown that our (human) circadian rhythms are influenced by blue light, and sleep schedule could be messed up.


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## troy (May 14, 2017)

What does too much blue light cause From the 6500k bulb?


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## naoki (May 14, 2017)

I'm not sure which target you are asking about, Troy.

For general plants: more compact growth: reduced leaf expansion, shorter internodes etc.

For orchids: not much info, but in some Phalaenopsis, production of certain defense chemicals was observed.

For human: reset the circadian rhythm. http://www.health.harvard.edu/staying-healthy/blue-light-has-a-dark-side
So too much blue light at night could cause problems in some people.

I'm not talking about fluorescent light, which has completely different spectra from 6500K LED.


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## troy (May 14, 2017)

Got it, thanks for the info!!


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## gonewild (May 14, 2017)

Kind of on topic....

Where does the color come from?

Is there a difference between a color emitting LED and a white LED with a color filter over it? Say a red LED or a white LED shining through red plastic.

Actually why I ask is I would like to know how much effect colored shade cloth might have on plant growth. I have green shade cloth over my plants and wonder if the green light hitting the plants is affecting growth.


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## naoki (May 14, 2017)

Lance, human eyes perceive a combination of photons with certain wave lengths as color. For example, most of recent white LEDs are blue LEDs with phosphors, so there is a blue peak and a yellow-red peak. There are also some white LEDs which uses green, blue and red monochromatics (so 3 peaks). Both of them look white for us. So our eyes can get tricked, and our vision might not reflect the real emission spectrum.

So in your example, red LED and filtered white LEDs may have similar spectra, but they are probably not identical. There are many kinds of filters, and it is probably possible to make something similar by combining them. But from plants, probably they would consider that these two light are similar.

Do the color of light look different under the colored shade clothes? If so, I would guess that it would influence the plant. When my friend was conducting an experiment to understand the shade avoidance response of plants, she had to be very careful to find correct pigments to make the shade.


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## gonewild (May 15, 2017)

naoki said:


> Do the color of light look different under the colored shade clothes? If so, I would guess that it would influence the plant. When my friend was conducting an experiment to understand the shade avoidance response of plants, she had to be very careful to find correct pigments to make the shade.



That's the thing to the eye the color does not appear green it just looks like shade. But photos taken under the shade have a strong green cast, So the digital chip is seeing the green color the human eye does not. 
How will this be seen by the plant? 
How are green shade cloth or green LEDs different than sunlight filtering down through a green leaf canopy in Nature?


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## naoki (May 15, 2017)

I don't know the answer, Lance.

Under canopy, don't you have excess of far-red (and blue)? One mechanism which some plants (and seeds) use to notice the canopy opening is the shift in red:far red ratio (phytochrome related response). So plants my have some physiological response depending on how shade clothes influence this ratio. But it is difficult to know this without a spectrophotometer (too expensive for most of us).

What they experience in the nature may not be the best for the plants. In other words, understory plants may be tolerating the non-optimum light.


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## Ozpaph (May 19, 2017)

There is quite a bit about shade cloth colour in horticulture. Some of it seems plant type specific but there is good evidence that white/light coloured cloth is best as it diffuses the light better. Conversely dark green and black are less optimal.


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## gonewild (May 19, 2017)

Ozpaph said:


> There is quite a bit about shade cloth colour in horticulture. Some of it seems plant type specific but there is good evidence that white/light coloured cloth is best as it diffuses the light better. Conversely dark green and black are less optimal.



I have not found any "non sales" info about how the color of shade cloth affects plant growth. if you have a link it would be great. i have seen some recent research that suggests green light from LEDs may adversely affect growth. But it was just a suggestion.


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## SlipperFan (May 19, 2017)

The reason plants look green is because they reflect green light - they don't absorb it. I suppose if they got only green light, they wouldn't be able to use it, so that would be an adverse effect. White light contains all the colors of the spectrum, so in that case, I doubt if green light is a problem, as long as the other colors are present.


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## Bjorn (May 20, 2017)

SlipperFan said:


> The reason plants look green is because they reflect green light - they don't absorb it. I suppose if they got only green light, they wouldn't be able to use it, so that would be an adverse effect. White light contains all the colors of the spectrum, so in that case, I doubt if green light is a problem, as long as the other colors are present.



Actually, they use green light as well, but less of it. So the reflected ligth contains more green, hence the green color


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## naoki (May 20, 2017)

There are two aspects; photosynthesis and photo-morphogenesis. Light spectra can influence the shape (and physiology of plants) in addition to photosynthesis. I think what Lance is talking about is the later aspect. But Bjorn is right that many plants seem to use green light, and the photosynthetic efficiency of green light isn't that low compared to blue light (maybe 10% lower).

In some plants, the stomata control is enhanced by blue light, but it get cancelled by green light. But other physiology seems to be influenced by green light, too. I don't think we know the mechanisms of how plants respond to green light. Some responses seem to be related to cryptochromes, which sense blue light. But I believe there are other possibilities including the existence of the elusive green sensor pigment. My friend from my undergrad era is one of the leading researchers in this field, but I haven't talked to him for a couple decades and I haven't checked the progress in this field. So I might be incorrect or out-dated.

But a lot of phytochrome (red/far red sensor) and cryptochrome related responses are frequently species specific (and not a lot of info for orchids).


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## Ray (May 20, 2017)

In addition to the fact that plants tend to reflect more (but certainly not all) green wavelengths than others, the human eye is more sensitive to green wavelengths than others, so of course they look so green.


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## gonewild (May 20, 2017)

I think maybe the answer is here:
http://www.amjbot.org/content/100/1/70.full


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## Ozpaph (May 20, 2017)

gonewild said:


> I have not found any "non sales" info about how the color of shade cloth affects plant growth. if you have a link it would be great. i have seen some recent research that suggests green light from LEDs may adversely affect growth. But it was just a suggestion.



LIGHT SPECTRUM MANAGEMENT USING COLORED NETS TO CONTROL THE GROWTH AND BLOOMING OF PHALAENOPSIS
Authors: C.A. Leite, R.M. Ito, G.T.S. Lee, R. Ganelevin, M.A. Fagnani
Keywords: spectrum, orchids, Phalaenopsis, morphogenesis, greenhouse
DOI: 10.17660/ActaHortic.2008.770.20
Abstract: 
The effects of blue, black and red shade nets on flowering and biomass production of several cultivars and hybrids of Phalaenopsis were studied. Plants aging from 6 months until the end of cycle and very young plants until the end of the cycle were tested. Flowering of all cultivars and hybrids, except one, was earlier and anthesis was reached sooner when grown under the red shade net as compared to the other two. Number of flowers was higher in plants grown under red shade net. Leaf surface area and the biomass of the leaves and roots were larger for plants grown under the blue shade net than the red and black net. These results suggest that the management of the spectrum can improve commercial characteristics in the Phalaenopsis plants.


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## Ozpaph (May 20, 2017)

http://hortsci.ashspublications.org/content/44/2/239.full


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## Ozpaph (May 20, 2017)

I found this interesting, too.
http://livingshade.com.au/2/blog/2013/06/17/climate-control-and-energy-savings/


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