It has been claimed that Plants grown under blended red and blue lights perform better and yield more than plants grown under either red or blue alone, or under full spectrum lighting.
In nature plants basking in natural sunlight receive both red and blue light along with all 7 colors of the rainbow. Indoor plants however are lacking in this smorgasboard of light.
Both red light and blue light are essential to producing healthy plants indoors. What we perceive as white light from the sun is actually comprised of all the colors of the spectrum. The three primary colors of the light spectrum are red, blue, and green.
Chlorophyll absorbs blue and red light while allowing green light to be reflected . The green light bouncing off of plants is how we see them as green, while purplish plants, which have a higher concentration of particular Phytochromes and cryptochromes tend to reflect / bounce off more red and blue spectrum light.
Blue light on plants enhances chlorophyll production and facilitates vegetative leaf growth. Red light and yellow aids flowering, fruit production, root growth, seed germination, and bulb development. When Red Light is lacking all of these processes are either stymied or simply do not occur.
When red light is too intense, chlorophyll synthesis becomes suppressed. A symptom of this is pale bleached out foliage, since chlorophyll is responsible for the green color of leaves.
A combination of blue and red light appears to produce the best results in the largest array of plants [Dual spectrum lights, which emits both blue and red light]. Now properly custom 'blending' the lights your plants receive can be a minor dilemma. Certain plants peform better with heavier doses of either blue or red at various intervals in their growth cycles.
Blue Light for Plant Growth
Flowering can be suppressed by using higher doses of blue light. This is helpful when growing leafy crops such as lettuce and certain herbs. Flower suppression enables a longer growing period before the plants go to seed and in most cases the foliage / leaves become unpalatable.
Blue light acts as a growth regulator, it also suppresses extension growth at the celleular level. The end result is that plants grown under blue light tend to be stubbier, shorter and have smaller, but more dense dark green leaves in comparison to plants lacking in blue light.
Red Light for Plant Growth
For some fruit producing plants heavier doses of red light is best as it expedites early flowering, which leads to longer active growing period for the fruit and hence more fruit over an extended period of time. Plants are more susceptible to fairly low intensity red light during their night cycles.
Red light increases the concentration of essential oils in plants. Some plants are of the highest quality when they produce a maximum amount of oils. The oils / essential oils create a more intense potency. Many medicinal, aromatherapy and culinary herbs fall within this category.
Dual spectrum lights
Adjusting the light ratios at strategic points in the plants life cycle can be advantageous and is generally not rocket science. Most lighting purchased for indoor or hydroponic gardening is set at a fixed ratio. However some newer LED systems are designed for maximum plant productivity, they allow for control of each color individually.
Red, Blue, Green, Far Red, ultra violet are all adjustable with the proper system.