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Re: [APD] Green HPS bulbs? No thanks.

> From: "Daniel Larsson"
> Sent: Sun, 19 Mar 2006 13:10:53 +0100
> ...I didn't use my ears, but my eyes...

That part of my posting was meant to describe these discussions in 

> ...This together with my eyes have convinced me long ago
> HPS:es are economically very bad...

> ...So true, but not if you want to really maximize growth
> to the energy you put in. I don't think NASA will use
> HPS:es when they will grow plants as fast as they can:

> ...This is not interesting for those that doesn't care when
> the electricity bill comes, they use HPS:ses or whatever
> crappy light they like the looks of and shoot as hard as
> they can. Brute force...

The only globe / tube - based lamp I'm aware of that is more efficient at 
converting electrical energy into massive amounts of light output are low 
pressure sodiums. On _what_ are you basing your economic comparisons?

NASA's energy constraints within the confines of a space vehicle are the 
dictating terms in their choices. Their choice of LEDs is based on energy 
consumption vs. desired goals, and they aren't as concerned with the 
comparative startup or initialization costs as they are with the effects on 
their on - board battery system. Since I don't have Bill Gates's bank 
account to use as a discretionary fund and don't ever intend to use massive 
and expensive batteries to run my tanks, this point is so moot that I just 
have to ask where you thought it figured into this debate.

Hydroponic and greenhouse concerns such as Tropica are well aware of the 
running costs of various lamps and their systems - they use them in numbers 
that we can only fantasize about in our everyday life. Plus they have well - 
utilized, well - educated and highly - motivated research staffs that make a 
living at this sort of thing. All geared toward producing the maximum amount 
of vegetative growth to create a product that, after going through several 
layers of middlemen, still only costs me an average of US $3.50 a pot. I 
imagine that, to them, a difference in fractions of a penny in just one 
single lamp choice can amount to hundreds of dollars' worth of electric bill 
one way or another. Which ultimately affects their profitability.

> You also think the phototropic response is due to the 440 nm
> length which is not true:

What I stated was that phototropic *response* was maximized at around 440 
nm. I never said absorption or utilization was maximized at 440 nm. Like a 
feedback mechanism, various combinations of factors may increase the 
pressure on the system to respond the farther away it gets from the optimal 

The paper you proffered does indeed discuss the odd effects of red and far - 
red light on phototropic response, but does nothing to either deny or 
confirm the _degree_ of the response as affected by blue light - only 
stating that the full effects of blue light and its receptors is not clearly 
understood but should be studied, as it clearly factors in for phototropic 

The effects of varying wavelengths of light, particularly in response 
patterns, have been studied for at least seven decades' worth of published 
papers, a good deal of which are available from the US Department of 
Agriculture. The first one of these that I remember reading was printed in 
1939, would probably take me some time to track down again, but it could be 
done. The more recent research deals with the specific mechanisms that make 
these responses possible to further our understanding, but does not 
automatically throw out empirical data collected over many observations 
based on simple Stimulus - Organism - Response reactions.

Considering all of the factors involved in the phenomenon we call 
"pearling", just what made you decide that the choice of lamps was the 
single- most _deciding_ factor?...


David A. Youngker
jaafaman at comcast_net

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