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[APD] Tough Actin' Actinic -- or - Home in the Range

Okay, so a little review work for me to dig up this:

Chlorophyll A responds to a range of the spectrum from
somewhere below 400  to 450 nm (peak at about 420nm) and in
the range 600-700nm (peak at about 640).

Chlorophyll B responds to a range of the spectrum from
somewhere below 400 to 490 nm (peak at about 480nm) and in
the range 600-700nm (peak at about 680nm).

A good actininc bulb has a range of about 380 to 480 nm
with a peak around 420 nm.

Other pigments in the chlorplasts are active arround the
680 and 700 nm range of the spectrum, but I don't know how
these relate to photosysnthesis -- speak up botanists.
Carotenoids are responseive to a range peaking at 520 nm
(near the green range).

It would seem that an actinic bulb, with the kind of output
I described above for a Philiphs actinic bulb, would
provide useful light to plants but only in a narrow zone at
the bottom of the lower range for each of the two kinds of
chlorophyll molecule.  When I look at the spectral graphs
for fluorescent bulbs, when I can find them, the 10,000K
bulbs have very high peaks in the 420 to 480 region,
although the peaks are usually narrow, much narrower than
the "blue" output from an actinic. There is also a peak in
the mid range (which make human eyes happy) and up in the
red zone where again the light is useful to both

Lower color temp triphosphors, from the graphs that I
recall, don't have nearly as high a peak in the 420-480 nm
range, or the "bluish" peak is at a longer wavelength, in
the 500s.

I would guess form this, and it's a sloppy guess, that with
lower color temp bulbs, the addition of an actinic might be
helpful -- of course, adding any bulb means your adding
more light so that complicates things. If you have, say two
bulbs and you take one out and put in an actinic, that wil
give the gcholorophyll plenty of light in the lower range
that they use but you would be dropping a lott of light
from the upper range that the chlorophyll use. 

It seems less likely with 10,000K triphosphor bulbs with
strong peaks in the 420-480 nm range. Adding an actinic
would be adding more light in that range, but it's less
needed with high color temp triphosophors so the effect
would be, I am again sloppily guessing, small -- and if you
remove a "regular" bulb so that the actinic isn't merely
adding more light, then it might make things worse because
of the substantially reduced output in the other range (the
reddish one) that chlorophyll use.

I am unconvinced about Hovenac's claim as it might apply to
5,000 K to 6500 K triphosphor bulbs and doubtful about it
for 10,000 K bulbs. But I'm willing to be convinced.

Scott H.

S. Hieber

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