Artificial lighting for plants: colour, quality and quantity

Light provides plants with the energy they need to grow and develop. Light flow is not consistent from one day to the next; some times of year are cloudier than others, and some regions get little sun. When natural light is not sufficient, artificial lighting is the perfect solution to ensure plants are healthy and strong. However, it must meet certain requirements.

Specifications for artificial lighting for plants

This type of lighting must meet a set of essential requirements that encompass parameters such as the light spectrum and the duration and quantity of light supplied.

The energy and technical efficiency of LED grow lights makes them a great option, providing huge energy savings and high light output in addition to having a long useful life and very low heat emissions. LED luminaires can also be adapted to suit specific situations by adjusting the wavelength of the light to optimise the luminaire based on the type of crop. One single LED can emit red and blue light to encourage optimal plant growth, thus eliminating the need for various luminaires.

Light spectrum

Plants are genetically programmed to grow when they receive sunlight. Though we perceive light as white or yellowy, it is in fact comprised of all the colours of the light spectrum. When these mix together, they produce the white light that we see.

Various studies have confirmed that not all light frequencies are equal when it comes to plant growth. In fact, specific frequencies, along with the intensity of the light, are responsible for said growth. The most effective frequencies on the light spectrum are those pertaining to red and blue light. Ultraviolet rays can burn leaves and severely compromise a plant. Hence, plant and crop producers usually use specific supplementary lighting to optimise plant growth without harming their integrity.
Let’s look at which light spectra have the greatest impact on proper plant growth:

Red

Red light has a wavelength of between 600 and 700 nanometres and is the second most important wavelength for plants. Since red light it not as effective on its own, it must be combined with blue light.
During the flowering period, plants are positively affected by red light in such a way that growth can be intensified and the number of leaves, fruit and flowers increased. Flowers are also bigger and stronger, and their colours more vibrant.
Infrared light also plays a key role in crop growth and development. The proportion of red and deep red light is a trigger for plants to start germination and also regulates the flowering time.

Blue

Blue is the most important light for plant growth. Chlorophyll absorbs it with ease and turns it into energy via photosynthesis. Blue light has a wavelength of between 400 and 500 nm and directly contributes to plant growth, from germination through to flowering. If plants receive only blue light, however, they will grow less tall and have darker colours. Blue light is much more effective when combined with red light.

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Light quantity and intensity

As already mentioned, the quantity and intensity of light are critical factors when it comes to plant growth and health. The amount of light emitted is measured of photons, while the total number of hours of light received in a complete day is called the photoperiod.

With these factors in mind, other key factors are the season and the local climate, i.e. cloudy or sunny.

We can put plants into three different categories: short-day plants, long-day plants and neutral plants. The first grow best with fewer hours of light, while the second require longer days and greater exposure to solar radiation. Neutral plants, on the other hand, are not affected by the photoperiod when it comes to flowering and branching.

Light quality

Light quality refers to the colour or combination of colours that make up the light and affect the crops in question. An optimal light combination benefits plant growth, flowering and branching. Blue and red light have the greatest impact on these processes, followed by yellow and orange. Green has the least impact; plants do not require green light and therefore reflect it. LED technology enables the provision of blue, red, hyper-red and far-red wavelengths at low cost.

Plant types

The intensity of light required – and therefore the power of the luminaires – depends on whether the plants are short-day, long-day or neutral. It may even be necessary to instal different types of luminaires. Indoor crops need more hours of artificial light than outdoor crops – between 14 and 18 hours to be precise. Plants and crops should not be permanently illuminated. Rather, they need at least six hours of darkness per day.

Luminaires should be installed taking into account plant growth. That is, the greatest possible quantity of light should reach the plants as uniformly as possible. 

Luminaires from Secom iluminación

Secom supplies specific luminaires for indoor plants. The PROTEK Q2 and KROP floodlights are designed for horticultural use. With a wide range of options and accessories, they can be adapted to all sorts of indoor crops to produce optimal results that not only meet but exceed the client’s needs.

LED technology facilitates high energy efficiency, adaptability and durability of artificial lighting for plants. Plant growth, flowering and branching are maximised, which in turn greatly increases the productivity, quality and financial return of the operation.

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