LED Grow lights
I bought a 225 LED fixture on eBay for 24.99 plus 8.50 shipping in January of 2009. It consisted of discrete red and blue LEDs. With a little google searching, I found the following light response curves.
Above: This is the response of the human eye to the light spectrum.
Above: These are the various plant processes sensitivity to the light spectrum.
From these two curves, we can see that the human eye has peak response at about 550 nm but plants do bes at the other two ends of the spectrum. The blue end stimulates chlorophyll while the red end is good for blooms and blossoms.
Voltage and current
The total power consumed by the panel is 8 watts. The small power supply puts out about 90 volts as measured by the Simpson meter. Each LED drops about 2 volts and they are attached in groups of 3 rows, or about 45 LED's to the power source. There are no individual resistorss on the LED's. Current must be limited by the large resistor on the power board.