Maximum Yield USA 2015 October | Page 56

WHEN REDS & BLUES COLLIDE “Understanding how to tilt the balance towards either red or blue at key points in the growth cycle can lead to important changes in plant physiology.” THE COMBINATION While each color of light has its advantages and disadvantages when it comes to plant growth, the overwhelming consensus is that a combination of blue and red light produces the best results. Plants grown under a blue-red light source will have a more typical leaf shape, have more biomass and experience higher rates of photosynthesis than plants grown under either color alone. High-quality LED grow lights will include both red (640-670 nm) and blue (430-450 nm) LEDs for maximum plant productivity. Some lights may be designed to deliver a fixed ratio of red and blue light, while others allow for control of each color individually. Manufacturers have even started to include far-red (730-740 nm) LEDs into their lights. Understanding how to tilt the balance towards either red or blue at key points in the growth cycle can lead to important changes in plant physiology. For example, controlling flower production can have dramatically different effects in the cultivation of different species. Suppressing flower initiation through blue-red light ratios is beneficial when growing lettuce, leading to a longer growth period with larger biomass when other factors such as temperature or photoperiod might otherwise trigger bolting. However, earlier flowering in strawberries may lead to more fruit produced over a longer period of time. Photobiology is the study of how light interacts with living organisms and is a growing field with new research being published every year. More information on how individual crops respond to specific light treatments can be found in horticultural science publications, many of which are made available to the public. 54 Maximum Yield USA | October 2015