Light is the ultimate source of energy used in photosynthesis for plant growth. But light can’t defined as one simple entity. The growth response is influenced by the quality, intensity and duration of the light.
The energy contained in light is absorbed in plants in the form of chlorophyll. Not all wavelengths of light are used with equal effectiveness. Looking at a chlorophyll/light absorption curve, one can determine that red and blue light are more effective than green. This is valid. Plants do not utilize all of the green light. It is reflected. This is why plants appear green.
When electric light sources generate light, the wavelength color is determined by many factors. For instance, a tungsten filament in an incandescent bulb produces more light with long wavelengths (the reds) when it is comparatively cool and more short wavelengths (the blues) when it is very hot.
Fluorescent tube lighting is the most economical and convenient in limited spaces. In the fluorescent tube, special phosphors become excited as electricity is supplied to them and emit energy in certain wavelengths. It is possible to engineer these tubes to emit primarily red, green, yellow or the “color” of your preference. Not all are equally effective, but this would appear to have a useful application, since plants do not use all wavelengths with equal efficiency.
To achieve superior efficiency in the response of plant growth to fluorescent light, special tubes have been designed which emit respectively more blue and red wavelengths of light. In doing so, the green-yellow-orange fraction has been condensed. The loss in this portion of the wavelength spectrum, even though it is marginally efficient has not been compensated by an adequate increase in the blue-red portion of the spectrum to result in improved plant growth.
Also, intensity affects the growth of plants. The brighter the light, the increase in energy the plant receives. To establish how much light a plant will need, consider where and how it grows best in its natural environment. Most vegetable and many mature flowering plants that grow in full sunlight need a high light intensity of 25 to 30 lamp watts per square foot. (A standard fluorescent tube provides 10 lamp watts per foot of length, so 40W, 4-foot fluorescent tubes a foot apart will supply 10 lamp watts per square foot.) The lamps should be positioned 8 to 12 inches above the plants and will provide about 800 foot-candles when positioned on 12″ centers.
Mature leafy house plants and growing seedlings will do healthy with 15 to 20 watts per square foot. Ten to 15 watts per square foot will be adequate for germinating seeds when required. This is considered low-intensity for plants but high-intensity for office or home lighting, which may be only 1 to 2 1/2 lamp watts per square foot.
Various plants are photoperiodic. This means they actually measure the length of each night and then yield either flowers or vegetation on the basis of this information. This reaction places them in classes as long night, short night or indeterminate plants.
Long night plants require 12 to 15 hours or more of darkness per night to flower. Short night plants usually need less than 10 hours of darkness to flower. Indeterminate plants will flower during all seasons of the year with no regard to photoperiod but typically require 12 to 18 hours of light for optimal growth. Although countless plants will grow under continuous light, almost all plants desire a dark period each day for maximum growth.
To summarize, fluorescent lights are ideal sources of light for growing plants in specific locations or spaces. Blue-red fluorescent tubes may stimulate a suitable response from some crops, but cool white light is as, or more effective for most crops. For some crops demanding especially high light intensities, the high energy discharge multi-vapor lamps should be considered as well as high output and very high output fluorescent tubes.
Spectrum Hydro carries a wide variety of Fluorescent Lighting for all your hydroponic needs.Shop All Fluorescent Lighting