page 581-583 .Etiolation i controlled by phytochromes. The plant measures|
the ration between 660nm and 730nm (different shades of red light)
vegetation absorbs and reflects almost all light below 700nm. Therefore the
amount of 730nm is much higher than 660 and the plat "feels" shaded and
begins to grow tall and thin and yellow (etiolated).
Lightbulbs radiate much light in the longer wavelengths, such as very
much infra red (heat radiation). And also sends out more 730nm than 660nm
and plants under only lightbulbs feel shaded.
Blue light is not involved in this adaptation.
page 574 But blue light (400-500nm) is the light that mediates phototropism
(ie the mechanism that makes the plant orients towards the light).
page 619-620: Blue light have long been shown to stimulate stomatal opening
in some plants independently of CO2. Evidence also exists that red light
stimulates stomatal opening by a slightly different mechanism.
My own opinions
Photosynthesis is best by blue and red light but different pigments helps
the plant to use other colors as well. I believe that when choosing light
one should avoid red light above 700nm as much as possible by removing all
incandescent lightsources ( except when etiolation is wanted). After that
it is more a matter of how much light we can give our plants and not so
much about color. The main reason to mimic daylight is that our plants look
more beautiful under it. Then looki att prices and design of fixtures and
Metal Halide looks good as daylight but HPS is more efficient lumens/watt
(but ugly-yellow). 250-400W is good economy but needs distance from plants
because of large amount of concentrated heat radiation.
I prefer Biolux fluorescent tubes (mimics daylight) but they are almost too
expensive. If you want good photosynthesis but feel that bright light would
be annoying in your room GroLux = FLUORA by Osram is a good option. =color 77
Said that, I do believe that ANY cool fluorescent light would be an
exellent light source. I am sure that 2 cool-whites is better that 1
GroLux, and much cheaper. The amount of light is more important than color
exept if red above 700nm! Blue (actinic) light can be used to make plants
open stoma and/or orient towards that light
Remember to add CO2. ( Indoors :-) ) Normal air only contains about 0,03%
so any addition would be appreciated!