new Led lights

[terryros]

The 680 and 700 nm absorption optimums for photosystem II and I are nicely in the redder part of the spectrum and would appear to be ideally covered by the dominant wavelength of the Natural White bulbs I am experimenting with (644-828 nm).

I think I remember reading that the blue spectrum absorption of chlorophyll (400-480 nm) developed in deeper ocean plants as an adaptive response to low and filtered light situations. Thus, it must do something, but maybe it isn't an essential part of the energy/sugar production cycle of the plant. However, I have heard anecdotally of orchids grown only under bluer light that have been vegetatively spindly and won't bloom but also of some grown only under high pressure sodium lamps (very little blue) that won't bloom. Since the Natural White LED bulbs that I am using are clearly not red, I am assuming they also have light in the shorter wavelengths, so with luck there will be enough bluer light to satisfy those picky orchids as well.

[Ray]

Most non-phosphor type LEDs DO have a "dominant" wavelength (some are very "pure" and do emit in a single one), but we should not confuse that with being the "color" of the light emitted.

I think the mushroom piece is incorrectly interpreting things. If you read the wiki article on Wein's law, it says the predominate wavelength can be predicted, but that does not tell you anything about the appearance of the light. Examples given includes the sun (5778°K) which calculates out to a predominate peak at 502 nm - right in the middle of the visible spectrum - and an incandescent bulb (1500°K) being 2000 nm, which is WAAAY in the infrared. If we took that to represent "the" wavelength that interacted with our plants, we would incorrectly conclude that an incandescent bulb can be of no value, as that 2000 nm does not correspond to any absorption by chlorophyll.

Earlier, it was mentioned that 644, 707, and 828 nm were the "dominant" color emitted by lamps of 3500°, 4100°, and 4500°K. Maybe I am TOTALLY missing something - and I have read the Wikipedia article to which we were referred by the mushroom site - but I still cannot buy the "color temperature relating to a single wavelength" assessment because none of those wavelengths correspond to white light at all - 644 nm is very red, while 707, and 828 nm are both in the infrared.

If you look at the spectra corresponding to those color temps (below), the peaks are, indeed, at the wavelengths the calculation would predict. But you can see that they do represent two IR and one red light, while the color we would see - due to the other wavelengths in the spectrum) are yellowish to bright white represented by the "appearance" dots associated with each.



There are a couple of other things to keep in mind:

1) Chlorophyll absorbs in the blue end of the spectrum too, and none of those light sources is particularly strong in the blue end.

2) Shifting to the "hotter" light gives you significantly more intensity of light in both of the chlorophyll absorption regions - including those tree specific wavelengths in the red/IR end.

[terryros]

Leaves me back in the completely experimental mode. I don't think I can gonto the hardware store and buy a cheap spectral analyzer for the bulbs! We know of one grower who has been using the MR 16 7 w bulbs for 4 months and has been getting excellent growth. Only time is going to tell whether I am close or far off with the choice. For now, I have headroom over plants, have eliminated my excess heat problem, and plants and flowers look their natural color under the lights. Many things are blooming, but this all started under fluorescents. I would guess I almost need a year cycle to know what works and doesn't work with the lights. I will then need to post a more detailed report.

[Ambrose]

Hi All,
I found the scientific paper at this link to be most interesting:

www.hcmiu.edu.vn/BME2010/Papers/P2.19.pdf

Happy Holidays, Ambrose

[Joey]

Hi, I am new to the forum. I really get into indoor trees but I also have some orchids. I have used a ton of different LED grow lights. Attached are a couple of pics from my living room, the experimental area. The "Grow UFO" type lamps are producing intense fruiting in the miniature orange tree even in the dead of Chicago winter. the real benefit is that you can get them right on top of the plant because of the low heat. With orchids I have only been able to make a plant bloom with red light. Just empirical info but my recommendation is to go heavily towards the red end of the spectrum. Keep in mind a lot of the LED products on the market are geared towards cannabis growers where you are trying to produce more vegetative growth at different times.

[DelawareJim]

Nice lghts. They look to be about 650nm? It prolly wouldn't hurt to add some blue in the 450nm range to catch both peaks for photosynthesis.

Cheers.
Jim