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HID lamps--HPS or Metal Halide?

Nobody nobody at hgmp.mrc.ac.uk
Thu Dec 9 09:31:13 EST 2004

I am student working on a project involving the efficiency of
artificial lighting in plant growth.  I am attempting to determine the
best-HID lamp sources for plants, mainly HPS and Metal Halide.

My current basic understanding of light and plants is this:
=B7	Plants use energy in different parts of the spectrum for
critical processes.
=B7	Red light powers photosynthesis, aids in seed germination,
helps to form pigments and aid flowering.
=B7	Plants can obtain energy to some extent from the entire visible
spectrum but obtain information particularly from the blue, red, and
far red regions
=B7	Photosynthesis is directly proportional to the photon fluence
=B7	Blue Light is always less efficient on an energy basis in
photosynthesis than red light.

My Questions:
=B7	If red light is more efficient for photosynthesis, then would a
light source, HPS, with a greater amount of "red" photons be better
than one with more "blue" photons and less red?
=B7	Is Photon Flux the most important factor to the plant in terms
of growth?
=B7	How important is the spectral distribution of the light to the
growth and health of plants?
=B7	Metal Halide, in general, has less photon flux than HPS,
however it has a more balanced Spectral Distribution.  If a hobbyist
were to use a single source indoors with no natural light, which light
source would be more appropriate?
=B7	If a person was to use HPS only, what is the minimum amount of
blue light the lamp would have to output in order for the plant to grow
naturally and not elongate?

Thank you for your time. I appreciate any help or information that you
can provide.
Please email me back at ala4 at cwru.edu.  Thank you.


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