Different plants and different plant parts depend on a variety of light colors. Different light colors provide varying levels of energy necessary for plant growth, development and function. As light energy is essential in photosynthesis through which plants create their own fuel for energy, understanding the significance of different color lights illuminates the relationship between form and function.
Different color lights stem from white light. White light encompasses every color of the spectrum created by the sun and manufactured in artificial lighting. When light passes through a prism, the entire span of colors is visible. This is much like when sunlight passes through raindrops and creates a rainbow. The colors include red, orange, yellow, green, blue, indigo and violet.
The different color lights are not simply a visible treat. Different color lights are actually different wavelengths. A wavelength, a measured unit of light energy, appears in longer and shorter measurements. The longer the wavelength, the lower the energy. The shorter the wavelength, the greater the energy. If you visualize a spectrum from left to right with violet on the left side and red on the right with the other colors filling in the rest of the line, you have a representation of a visible light color spectrum. The spectrum is a descending scale of energy from left to right. Different color lights are responsible for different functions during plant growth as each part of a plant absorbs varying levels of light energy, or light color, for its particular function.
When you look at a plant, it displays color. However, those colors are not expressed from within the plant, but are actually a reflection of the different light colors the plant does not absorb. Plant pigments are light-absorbing molecules. A plant receiving necessary light will grow successfully and exhibit vivid color. If a plant is not receiving adequate light, it may appear dull.
Chlorophyll is the pigment in plants responsible for creating a green appearance. Chlorophyll absorbs all light colors except for green light. The green light is reflected from the plant and seen by the human eye. The energy absorbed by chlorophyll is taken from violet-blue and red wavelengths and is a main factor in photosynthesis, the process by which plants transform light into plant food for consistent growth. Plants that display other colors, such as orange plants, absorb different color lights due to their particular makeup and energy needs.
When not relying on the sun for its full spectrum of different color lights, you must identify the appropriate color lights for optimal growth. Since most plants reflect green light, this is the least effective color light in aiding plant growth, according to the University of Arizona Cooperative Extension. Red and blue light combinations promote flowering. Blue light encourages leaf growth by offering energy highly used in photosynthesis. When utilizing artificial light, choose fluorescent lights for seedling growth as they provide cool-white light color. A broad-spectrum fluorescent light offers a greater amount of red light, and is, therefore, well-suited for flowering plants, according to the Colorado State University Extension.