stardustsailor
Well-Known Member
,but fresh for NASA ...
http://ntrs.nasa.gov/search.jsp?R=20150009399
Publication Date: May 31, 2015
***sole source of lighting (SSL),for NASA ...
.................................
(...)
Red light.
The most staple waveband of light that anchors SSL LED arrays for plant growth is red.
Broad-band red (600-700nm) light has, by far, the highest quantum
efficiency for driving photosynthesis, with a broad peak from about 620 to 660 nm
(11). As well, red has numerous photomorphogenic effects on plant development
mediated by the photoreversible pigment phytochrome.In general, red light
promotes stem elongation, leaf expansion, biomass accumulation, and contributes to
a phytochrome photostationary state (PPS) that can determine flowering, dormancy,
and other important photomorphogenic responses of plants, including seed germination.
(...)
600 nm to 700 .... That is the most wanted band for red ...
Either from monos mix ( 600 nm -620 nm -640 nm -660 nm -680 nm -730 nm )
or from a broadband red ( nitride ) phosphor ...
(...)
Blue light.
There do not seem to be any simple answers regarding how little or how
much blue light is required in an SSL prescription for any given plant species, or even
when to apply it during a given plant life cycle. Even though
approximately one-thirdof sunlight PAR emissions consist of broad-band blue (400-500 nm), plants grown
outdoors seem to be not particularly sensitive to blue light, at least at outdoor light
intensities (12). Under SSL conditions, however, which tend to involve much lower
PPFs than outdoors, the intensity of blue light seems to be a critical factor. Sometimes
only a few percent of blue are needed for a particular plant response, above which
blue is inhibitory, but that may change during the course of a plant’s life cycle.
Plant-growth functions that seem to be particularly sensitive to blue light in SSL situations
include stem elongation and leaf expansion, with “too much” blue inhibiting growth
in both cases (13). Other plant responses having an absolute requirement for blue
light include phototropism, stomatal aperture, leaf thickness, and chlorophyll content.
Effects of blue light on secondary product metabolism are mentioned in the section
on value-added for SSL.(..)
So.... no need for blue LEDS ?
(...)
Green light.
Green light (500-600nm) falls between broad-band blue and red light
along the PAR energy spectrum. Green often is disregarded as an unimportant
waveband in photosynthesis because absorption spectra of extracted leaf chlorophyll
pigments indicate very weak absorption in the green region of the PAR. Because
chlorophyll has major absorption peaks only in the red and blue regions, researchers
initially selected first red, later blue, LEDs for first-generation LED arrays to support
plant growth. However, intact leaves do absorb considerable green light, and in a
relative quantum-efficiency curve for photosynthesis vs. PAR wavelengths, some
wavelengths of broad-band green actually are more efficient than certain
wavelengths of the blue band. Overall, however, broadband green is slightly less efficient than broadband blue. However, when leaf canopies close, red and blue light are absorbed strongly by upper or outer leaf layers, whereas green light penetrates to interior leaf layers, where it subsequently is absorbed and drives photosynthesis of the inner canopy (14). Thus, light sources containing some green can be more effective in stimulating crop growth than are red + blue sources alone,much as when
foliar canopies are closed. When applied together with blue light, green has effects
opposite to blue on stomatal aperture (15). Yet another useful feature of green light
is that the human eye perceives red + green + blue (RGB) light as white light, so if all
three wavebands are present simultaneously in plant-growth light, researchers and
growers are able to visually evaluate the stress status of crops, the incidence of
physiological disorders, and “true” leaf color (the way it looks outdoors), whereas if
only red + blue are present, green tissue looks purple, grey, or black, and
physiological stress or disease diagnosis is difficult(...)
Naf said ...
(...)
White light.
The often-confusing issue regarding which colors or proportions of
colors to select for SSL applications with LEDs can depend on species, cultivar, stage
of development, and intensity of available light. In some ways, the use of LEDs for SSL
is causing us to rediscover the value of white light for plant growth and development.
Because of all the complications involving LED color selection and the range of
possible plant responses, the question often is asked regarding whether white should
be the LED color of choice for plant growth. It turns out that white LEDs actually are
blue LEDs with a phosphor coating the inside of the light-focusing lens mounted over
and around the diode. Energy losses associated with the secondary broad-band
photon emissions of the excited phosphor make white LEDs significantly less
electrically efficient than emissions from pure monochromatic blue LEDs (16). As
well, the proportions of red, green, and blue wave
bands in white LED light vary widely among cool-white, neutral-white, and warm-white LED types,
none of which are a close match for the RGB distribution of midday solar light. It actually would be
more electrically efficient to make white light from monochromatic RGB LEDs than to
use white ones. Nevertheless, inclusion of a few white LEDs on an array may have
utility in terms of achieving certain proportions of broad-band color in case green LEDs are not included.
(...)
In few days ? weeks ? months ? years ? ..they will discover COBs ..
And by then ,maybe the special tailored COBS for horticulture are also widely available ....
Which by allowing the growers to manipulate different channels ,
aka different sections of the LES ,either of monochromatic dies ,
either special phospors or both ....
Then any solar light can be emulated ..
Dawn ,noon ,midday ,dusk ...And much more ...
http://ntrs.nasa.gov/search.jsp?R=20150009399
Publication Date: May 31, 2015
***sole source of lighting (SSL),for NASA ...
.................................
(...)
Red light.
The most staple waveband of light that anchors SSL LED arrays for plant growth is red.
Broad-band red (600-700nm) light has, by far, the highest quantum
efficiency for driving photosynthesis, with a broad peak from about 620 to 660 nm
(11). As well, red has numerous photomorphogenic effects on plant development
mediated by the photoreversible pigment phytochrome.In general, red light
promotes stem elongation, leaf expansion, biomass accumulation, and contributes to
a phytochrome photostationary state (PPS) that can determine flowering, dormancy,
and other important photomorphogenic responses of plants, including seed germination.
(...)
600 nm to 700 .... That is the most wanted band for red ...
Either from monos mix ( 600 nm -620 nm -640 nm -660 nm -680 nm -730 nm )
or from a broadband red ( nitride ) phosphor ...
(...)
Blue light.
There do not seem to be any simple answers regarding how little or how
much blue light is required in an SSL prescription for any given plant species, or even
when to apply it during a given plant life cycle. Even though
approximately one-thirdof sunlight PAR emissions consist of broad-band blue (400-500 nm), plants grown
outdoors seem to be not particularly sensitive to blue light, at least at outdoor light
intensities (12). Under SSL conditions, however, which tend to involve much lower
PPFs than outdoors, the intensity of blue light seems to be a critical factor. Sometimes
only a few percent of blue are needed for a particular plant response, above which
blue is inhibitory, but that may change during the course of a plant’s life cycle.
Plant-growth functions that seem to be particularly sensitive to blue light in SSL situations
include stem elongation and leaf expansion, with “too much” blue inhibiting growth
in both cases (13). Other plant responses having an absolute requirement for blue
light include phototropism, stomatal aperture, leaf thickness, and chlorophyll content.
Effects of blue light on secondary product metabolism are mentioned in the section
on value-added for SSL.(..)
So.... no need for blue LEDS ?
(...)
Green light.
Green light (500-600nm) falls between broad-band blue and red light
along the PAR energy spectrum. Green often is disregarded as an unimportant
waveband in photosynthesis because absorption spectra of extracted leaf chlorophyll
pigments indicate very weak absorption in the green region of the PAR. Because
chlorophyll has major absorption peaks only in the red and blue regions, researchers
initially selected first red, later blue, LEDs for first-generation LED arrays to support
plant growth. However, intact leaves do absorb considerable green light, and in a
relative quantum-efficiency curve for photosynthesis vs. PAR wavelengths, some
wavelengths of broad-band green actually are more efficient than certain
wavelengths of the blue band. Overall, however, broadband green is slightly less efficient than broadband blue. However, when leaf canopies close, red and blue light are absorbed strongly by upper or outer leaf layers, whereas green light penetrates to interior leaf layers, where it subsequently is absorbed and drives photosynthesis of the inner canopy (14). Thus, light sources containing some green can be more effective in stimulating crop growth than are red + blue sources alone,much as when
foliar canopies are closed. When applied together with blue light, green has effects
opposite to blue on stomatal aperture (15). Yet another useful feature of green light
is that the human eye perceives red + green + blue (RGB) light as white light, so if all
three wavebands are present simultaneously in plant-growth light, researchers and
growers are able to visually evaluate the stress status of crops, the incidence of
physiological disorders, and “true” leaf color (the way it looks outdoors), whereas if
only red + blue are present, green tissue looks purple, grey, or black, and
physiological stress or disease diagnosis is difficult(...)
Naf said ...
(...)
White light.
The often-confusing issue regarding which colors or proportions of
colors to select for SSL applications with LEDs can depend on species, cultivar, stage
of development, and intensity of available light. In some ways, the use of LEDs for SSL
is causing us to rediscover the value of white light for plant growth and development.
Because of all the complications involving LED color selection and the range of
possible plant responses, the question often is asked regarding whether white should
be the LED color of choice for plant growth. It turns out that white LEDs actually are
blue LEDs with a phosphor coating the inside of the light-focusing lens mounted over
and around the diode. Energy losses associated with the secondary broad-band
photon emissions of the excited phosphor make white LEDs significantly less
electrically efficient than emissions from pure monochromatic blue LEDs (16). As
well, the proportions of red, green, and blue wave
bands in white LED light vary widely among cool-white, neutral-white, and warm-white LED types,
none of which are a close match for the RGB distribution of midday solar light. It actually would be
more electrically efficient to make white light from monochromatic RGB LEDs than to
use white ones. Nevertheless, inclusion of a few white LEDs on an array may have
utility in terms of achieving certain proportions of broad-band color in case green LEDs are not included.
(...)
In few days ? weeks ? months ? years ? ..they will discover COBs ..
And by then ,maybe the special tailored COBS for horticulture are also widely available ....
Which by allowing the growers to manipulate different channels ,
aka different sections of the LES ,either of monochromatic dies ,
either special phospors or both ....
Then any solar light can be emulated ..
Dawn ,noon ,midday ,dusk ...And much more ...
. In that sense, photoperiod lighting is SSL, even in the greenhouse. Far-red wavelengths also have photomorphogenic effects on stem elongation, with a low R/FR ratio favoring
