A Quick Lesson in Light
Sunlight appears 'white' until you push it through a prism. This refracts – or fractures – the light into its color spectrum, otherwise noted as the 'rainbow'. The rainbow, however, is the basic primary range of colors, with others that are invisible to the human eye – infrared on the low frequency or 'red' end and ultraviolet on the high frequency or 'purple' end of the spectrum.
Why Are Plants Green?
As discussed, every object has specific colors that it does not absorb. Plants typically do not absorb green light from the spectrum, which causes the leaves and stems to appear green. While this is likely due to the chlorophyll produced in the process known as photosynthesis, it seems that chlorophyll does not absorb green.
Photosynthesis is the process plants use to create their own food for growth. Using light, they go through a process that creates sugar on which they feed, causing them to grow. During the process, plants utilize a combination of chlorophyll, light, and water to create food that has a green pigment, leading to their coloration, and generate the air that we breathe. It's a digestive process, much like all organisms have, with its own special configuration, and plants can grow stronger and fuller with specific types of LED grow lights provided at the right stages of growth.
Far-Red or Infrared Light
Plants use this to sense the density of plant population where they grow, which affects germination, or seed production. In fact, low levels of infrared light cause plants to 'pause' the germination process, noting that there is already a large population, and therefore, will not produce seeds under such conditions.
Colors That Don't Matter
Some of the areas in which red light are necessary include:
Hormone production – High levels of red light received during early growth produces meta-topolin, a hormone that prevents the breakdown of chlorophyll. This is precisely what a young
plant needs to grow larger and stronger, since the chlorophyll is necessary in the process of
photosynthesis in order to create adequate food (sugars) for the plant as it grows. The excess
chlorophyll also keeps the plant very green, providing its health during this period.
Flowering and germination – Plants 'compare' the amount of red light to the amount of infrared light to determine if it should germinate or flower. If your plants are exposed to excess red light during the 'dark' period, you'll find that you'll have to wait longer to harvest from it, which is definitely not ideal. This is especially true of cannabis, which is part of the reason you'll find it ill-advised to enter the growing space during dark periods.
Seed type – Most growers want to produce female seeds (where applicable). While red light is incredibly important to the growth process, you don't want overexposure because too much red light can cause most seeds to grow into male seeds.
Flavor – For leafy greens, microgreens, herbs, and cannabis, you'll want to control the amount of red light based on the flavor you want to produce. Large amounts of red light produce larger amounts of certain oils, which can create a specific taste, usually causing
more bitterness in the flavor. While this may be desired in some plants, others will be less desirable. Determine your needs based on the types of plants you're growing.
Hormone production – While red light produces a hormone that helps with photosynthesis, blue light decreases production of auxin. Auxin controls the growth of the stem as well as controlling the process of apical dominance, or the way a plant controls growth points and keeps buds from intertwining and creating a mess of excess branches. The overall effect of dampening auxin operation is that plants remain shorter and grow thicker and wider, which is
what you want for sturdiness in the early growth stages.
Increased metabolism – The amount of blue light available to a plant determines how far the stomas – or pores in the epidermis or skin of the plant – open. These pores are used to take in carbon dioxide and release oxygen. With more blue light, the stomas are opened wider, which increases the metabolism of the plant, thereby accelerating growth and production. This is important during the flowering stage, creating more buds or flowers for harvest.
Growth direction – Blue light attracts plants, so you'll find that wherever the blue light is
located, your plants 'reach' for it. This can help you assure that your plants are growing 'up'
in the direction you desire.