Sunlight is, simply and easily put, light from the sun. There are all sorts of scientific ways to measure sunlight, and define it. But for the average human being gardener, sunlight is the amount of light that shines on our vegetables. Plants need the sun shining down on them to undergo photosynthesis- the process of using the energy of sunlight to change carbon dioxide into organic compounds that the plant uses as food. The byproduct of this process is oxygen. Without the light from the sun, our earth would not be able to sustain life. Plants would not be able to survive, and water would turn into ice because of the lack of heat. Our basic necessities to live on earth stems from this interconnectedness of all these processes.
When it comes to indoor gardening, we have to replicate sunlight as much as possible with artificial lighting systems. The sun seems to be a blazing ball of yellow or orange light, but the light emitted from the sun contains a broad spectrum of colors. Plants react to these colors in different ways. Plants associate the bluer end of the spectrum with spring. This spectrum promotes vegetative growth in plants. The redder end of the spectrum is associated with autumn, and this encourages plants to produce more flowers than leaves.
Indoor gardening lights come in different wattages, emits different spectrums, and tries to replicate natural sunlight as much as possible. There are many different kinds of grow lights available for the indoor gardener. One of them is the High Intensity Discharge light. This is one of the most efficient lights available today, and any serious grower will have one of these in the grow room. HID lights produce an intense light, and replicate sunlight as much as humanly possible.
Another type of lighting system available for the indoor gardener is the Metal Halide light. These have a balanced spectrum. The Metal Halide light bathes plants in light from the bluer end of the spectrum, and also provides some light in the red/orange spectrum.
Grow lights are an essential part of an indoor garden. Any serious grower will have at least one professional light for maximum growth and health. If the plants are supposed to flower or produce fruit, it is important to consider a light that has a balanced spectrum.
Like sunlight to life on earth, indoor gardening lights are essential to life in your garden.