Lights - High Pressure Sodium AND Metal Halide |
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Photosynthesis is the process by which plants use light energy to collect carbon dioxide from the atmosphere and convert it to chemical energy in the form of sugar. The products of photosynthesis serve to nourish the plant and enable it to release free oxygen. Plants use only the spectrum of light that is visible to the human eye. Although the light appears white, it is actually a mixture of all the colours of the rainbow. Pigments, which are the light harvesting units of the plants, absorb certain colours of the spectrum and reflect the rest. Chlorophyll, the main pigment used in photosynthesis, absorbs light in the violet and blue wavelengths as well as in the red, leaving green the colour it reflects, and the plant colour we see. Photosynthesis can also occur indoors, providing the artificial light source used supplies the necessary spectrum and intensity.
Wide spectrum fluorescent, metal halide, and high pressure sodium are the types of lights most widely used for indoor growing. All of these lights require a ballast to operate and come in a variety of sizes and wattage's.
The more "intense" your light source, the further down into the foliage the light can penetrate. 1000 watt Metal Halide Lamp will penetrate through more foliage and give you buds on alMost your entire plant. 400 watts will give you sweet buds at the top of the plant, but the light isn't intense enough to create buds on the entire plant. a 600 Watt system works pretty well, but not as powerful as the 1000 watt. Generally, most growers use fluorescent lights for seedlings. Fluorescents are not intense enough to promote vigorous flower formation and can cause older seedlings to wilt because the light is not providing enough nutrition.
So during vegetation you use Metal Halide lighting.
Metal halide lamps emit light closer to the blue end of the spectrum and because of this, they are the preferred lamp for the vegetative stage of growth creating a shorter and plant with a strenghtened stalk. The taller your plants grow indoors, the more difficult it becomes to get a good yeild. You'll see your plants stretching higher towards the light souce if it isn't the right intensity or spectrum. The stretching causes more distance between buds and decreased yeild. The light emitted by a HPS is closer to the red end of the spectrum, which is what the plant craves during the flowering stage. High Pressure Sodium is used during flowering beacause it increases bud size by up to 15%. If you don't have the budget to purchase both a MH and a HPS for your grow setup, just use a MH for both the vegetation and for flowering.
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