The Plants absorbs light in blue & red and from what was i looking in american lighting manufacturer i was noted the all of their plant growing lamps are not produce well these wavelength. for example SUNMASTER lighting has metal halides with colors that most plants are invisible to them or EYE hortilux that the BLUE mode is actualy contain regular general porpuse daylight with most of the energy come in th green part of the spectrum which plants are invisible & the HORTILUX METAL HALIDE that has the standard cool white of the sodium scandium the produce only a pitfull amout of light for the plants. Why?

From http://ioannis.virtualcomposer2000.com/spectroscope/elements.html

"Plant Growth: The optimal choices are the PLANTA specialized metal halide, followed by the tungsten halogen, the color corrected mercury and the blended light lamp. Although many people who grow plants think that the high pressure sodium lamp is a good choice, the above choices easily outperform it because their spectrum matches the photosynthesis curve better, so there's no need to spend a fortune for plant growing if one knows what to look for (even though the PLANTA metal halide is not that cheap)."

So to summarize, if you don't want to spend a fortune on a plant growing lamp, get a coated  MV lamp.

It is my understanding that plants are most sensitive to the red and blue part of the spectrum, but, they also seem to need all the other parts as well. The sun has the complete spectrum and plants have evolved for millions of years to utilize this energy. The problem with HID lighting such as mercury, metal halide, or fluorescent is the mercury in either lamp types create strong spectral lines in the green and yellow. And so, as green is reflected and yellow is minimally utilized, it is very hard to perfect a good artificial grow light. And, BTW, AFAIK, mercury vapor does not make for a very good grow light...but then I've never really tried it.