plants in red, blue, green, white light and darkness???

Question

what do plants look like in red light
what do they look like in blue light ... green? white? and darkness?
in which lights are they green with chlorophyll and can perform photosynthesis?!?!

Answer 1

Chlorophyll a absorbs its energy from the Violet-Blue and Reddish orange-Red wavelengths, and very little from the intermediate (Green-Yellow-Orange) wavelengths. It absorbs all wavelengths of visible light except green, which it reflects. Chlorophyll absorbs between 350-700 nm with peaks at 450 & 700nm. Plants respond most to light in the blue (400 to 450nm) and especially the red (625 to 675nm).

White light is a full spectrum so plants look as they do under sunlight. Without light they would die.
If a plant is grown in only a portion of the full spectrum it will not grow as well. Therefore interrupting any color of the spectrum will reduce plant growth.
If you use a grow light like a Metal halide bulb it will produce an abundance of light in the blue spectrum. These are good for foliage plants. These are used when there is little or no additional sunlight so are capable of growing a healthy indoor plant with no other light source. The plants appear blue green compared to outdoor light.
Red spectra lights are used to encourage blossom & fruit. Red spectrum of high pressure sodium are actually across the entire red & orange range of the spectrum so are used as secondary lights to fill in natural light conditions that are insufficient for flowering. If they were used without additional light they would grow quite well but may become elongated. Short wavelength UV (290 to 310nm) is a factor in preventing plant elongation. The plants would be more prone to fungal growths also without the UV. The light you perceive would make the plants look reddened or browner, not true green. They do not look as healthy to our eyes as with the halide bulbs despite good foliage.
If you used a bulb emitting light only in the green range chlorophyll reflects the plants would appear green for a while but without other parts of the spectrum they would rapidly die.

Chart of plant growth and wavelength
http://www.clovis.co.uk/horticultural/images/graph_lwpg.jpg
http://www.clovis.co.uk/horticultural/polythene_film_facts.htm

Greenhouses are sometime covered in tinted films, usually green, to diffuse the light while transmitting the maximum amount of solar radiation for the plants to absorb.
http://www.clovis.co.uk/horticultural/images/graph_ltcf.jpg

Answer 2

Green plants are green because they (well, the chlorophyll) REFLECT green wavelengths of light. Chlorophyll however, absorbs red and blue wavelengths of light (that's where it gets the energy for photosynthesis), and also some yellow/orange.

In white light (daylight) plants would be green, in green they'd look green, in red or blue they'd look dark - possibly almost black but I can't say exactly what colour, you'd have to try it. In darkness, well, no light so you couldn't see 'em!

Photosynthesis should occur in white, red and blue light, but not green or darkness.

You can see the light requirement for photosynthesis (by the build up of starch) by part covering a leaf with metal foil or black paper then doing the iodine test.

Answer 3

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