THE INFLUENCE OF
ON PLANT GROWTH
With a plethora of grow light options on the market , knowing what light to buy can be confusing . Alex Fraser explains how the different spectral light ranges impact plant growth and health .
by Alex Fraser
Expert growers have always known that light plays a crucial role in plant growth and development , but until recently there weren ’ t many options regarding the color spectrum of lighting technology available . With the rise of affordable , high-efficiency LEDs the choices are practically endless , and manufacturers have rushed in to supply nearly every thinkable flavor of lighting , all claiming to have the ideal spectrum for fast growth and heavy yields . Fixtures featuring tunable spectra allow the grower to dial in custom light recipes , which often only adds to the confusion over what is best for the plant . To understand how spectrum influences plant health , it ’ s important to have some basic knowledge regarding light and photosynthesis . In the simplest terms , plants use energy harvested from sunlight to combine CO 2 and water to produce sugars and oxygen . These sugars are used by the plant for energy and to build biomass . Rigorous university studies have shown that it takes a minimum of 10 photons ( particles of light ) to absorb one molecule of CO 2 . It turns out this rule holds true regardless of the color of photons the plant receives as long as they are within the visible range ( 400-700nm ). In other words , at a given intensity , plants can perform about the same amount of photosynthesis under any color of light . Spectrum plays a very important role in the shape and structural development of the plant ; this relationship is known as photomorphogenesis and it is the subject of many ongoing studies . Although plant structure is separate from biomass production and yield , the shape of the plant can have an impact on how the plant receives light , and so the two are often interdependent .
Spectral Light Ranges and PLANT DEVELOPMENT
Let ’ s take a look at the different spectral ranges of light and how they affect plant development .
INFRARED ( 800nm-1mm ) — The majority of photons produced by traditional light sources such as high pressure sodium ( HPS ) and metal halide ( MH ) are in the form of infrared ( IR ), which accounts for their inefficiency compared to modern LEDs . While infrared photons can ’ t be harvested for energy , they have the effect of warming up plant surfaces which increases transpiration and speeds up some metabolic processes .
62 Maximum Yield