Everyone seems to have an opinion on the proper lighting system for hydroponics, but few actually tell anyone why light is so important. It may seem like a given, but the relationship between plants and artificial light is a complex one. The level of light can make a big difference in the growth and health of your crop. It’s important to not only understand what systems are available, but why light is critical to a hydroponic garden.
It’s All About Photosynthesis
Elementary school taught us that plants need light to survive and fuel photosynthesis. Photosynthesis has two cycles that must be completed for a plant to grow: a light cycle and a dark cycle. The light cycle is when the plant is absorbing light from the outside and storing it like a battery in the form of glucose.
Once that battery is full, the plant begins the dark cycle which transforms the simple glucose into sugars and complex carbohydrates. In nature, this traditionally follows the standard day and night cycle, but in hydroponics we can keep light on it 24-7 if needed and still create the necessary dark cycle.
Growth And Wavelengths
Light comes in a variety of wavelengths and plants react to those wavelengths. Light created within a specific range of wavelengths can dramatically increase the growth rate. Plants have optimum growth between wavelengths of 435-675 nanometers. Planters want to create a lighting system that falls somewhere within that spectrum.
In fact, different wavelengths can activate certain processes in the plant including non-visible ultraviolet light. Hydroponics requires the careful use of these wavelengths throughout the growing process.
The Dark Cycle is supposed to be in the absence of light, but through hydroponics, we’ve discovered that light can enhance the dark cycle. The light emits infrared radiation that increases the chloroplast temperature in the leaves and is actually good for photosynthesis. So, by having a longer light cycle, the entire process of photosynthesis can be extended and enhanced.
Light also helps trigger certain hormonal changes in the plant that help begin the flowering phase. Longer lighting periods will not aid this, so gardeners keep light periods high during the vegetative state and drop it down to 12-hour shifts when flowering.
Light and Carbon Dioxide
The day cycle of photosynthesis has been likened to a battery, but once that battery is full the light is wasted. By increasing the levels of carbon dioxide during the light cycle, the battery size will increase. The plant will be able to absorb and convert more light energy for the dark cycle.
In order for this to work, the photons (small packets of light) must come from the red and blue wavelengths.
Photosynthesis is a complex process that every plant utilizes each day and light is an essential part of that process. Gardeners must understand how light interacts with the plant and at what levels and wavelengths to maximize the growth potential of the plants. It’s a delicate balancing act where too much or too little can have a major impact on your crop.