LED Grow Lights

Light for plants

Human eyes perceive wavelengths in the range of 380 nm to 780 nm. Humanscan distinguish between different light intensities and different colors. Green light (555 nm) is detected more sensibly than other colors.

Radiation effects to plants include physical effect radiation (300 – 800 nm) and photosynthetically active radiation (PAR = 400 – 700 nm). Plants mainly absorb red light and blue light while reflecting green light. Because of this, plants appear green.

Range of effects that
light has on plants
and animals

Chlorophylls absorb light in the range of 400 nm to 700 nm, which is important for photosynthesis. At the same time, light of different colors plays an important role for a healthy development and growth of plants. The shape and form of a plant is influenced by the light that the plant receives. For example, the number of leaves and the length of stem vary, depending on the color and the amount of light that is available. This process is called photomorphogenesis.

On top of that, the length of day, or to put it differently, the duration of light exposure, also influences the development of the plant.

Many plant species do not flower unless the length of day exceeds or, alternatively, falls below a certain value. Animals can also be influenced by light.

For example, light of certain wavelengths can be used to bait fish. Likewise, light of certain colors can attract or repel insects. This can be very useful in horticulture. For example, blue light and UV light can be used to attract insects to catch a pest in a trap.

What light intensity is required for a healthy growth of plants?

Light intensity is usually measured with the unit “lux”. However, it’s not recommended to use this unit when talking about light that is required for photosynthesis, because the lux has been developed for electric lighting that is used to illuminate human living spaces and is therefore based on the human perception of light and colors.

Humans and plants perceive light very differently.

The human eye is most sensitive to green light. At the same time, green light is very inefficient for photosynthesis. This means, white light with a large portion of green light can seem very bright to human eyes, produce a high value on a lux meter and still be unsuitable for driving photosynthesis.

To overcome this problem, a new unit, specifically for photosynthesis, has been developed. The name of the unit is PPFD, which is an abbreviation of “Photosynthetic Photon Flux Density”.

PPFD measures the quantity of photons with wavelengths between 400 nm and 700 nm that fall on a particular surface. Therefore, PPFD is given as µmol per square meter and second, which is abbreviated as µmol * m-2 * s-1.

In the following table, you can see the light compensation point and the light saturation point for different plant species. The values are given as PPFD and as lux.

However, keep in mind that it is not possible to convert PPFD into lux and vice versa with a simple formula. The conversion rate of PPFD into lux depends on the spectrum of the light source. This table is based on fluorescent light.

This table can give you an idea what light intensity is right for your plants.

Light compensation point and light saturation point for different plant species

The difference in efficiency
between classic lighting and
PARUS LED lighting

As explained above, it is not possible to convert PPFD into lux with a simple formula, because the conversion rate depends on the spectrum of the light source. A light source that primarily produces photons within the red and blue portion of the light spectrum will be much more efficient at driving photosynthesis than a light source that also produces green light.

Nonetheless, both light sources can produce light that appears white to the human eye. With modern LED technology, it is possible to produce light that is composed of narrow bands of certain wavelengths, which are most effective at driving photosynthesis.

Consequently, it is possible to engineer a light that has a very low power consumption while still increasing photosynthesis intensely.

This is exactly what PARUS has done.

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Characteristics and application
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