How does light affect plant growth?

Three parameters of light are relevant for a plant: quantity, quality and duration. Each of these parameters has a different influence on the plant performance:

Light Quantity (intensity)

Light quantity or intensity is the main parameter which affects photosynthesis. Photosynthesis is a process used by plants to convert light energy into chemical energy that can later be released to fuel the organisms’ activities.

Light Quality (spectrum)

Light quality refers to the spectral distribution of the radiation, i.e. which portion of the emission is in the blue, green, red or other visible or invisible wavelength regions. For photosynthesis, plants respond strongest to red and blue light. Light spectral distribution also has an effect on plant shape, development and flowering.

Light Duration (photoperiod)

Many flowering plants sense seasonal changes in photoperiod, which they take as signals to flower. Flowering can thus (partially) be controlled by changing the light duration.

Each Of These Parameters Can Be Adjusted Precisely With Qaledo-horti Lights


All our lamps are dimmable with a 1-10V or a PWM signal.

Custom Spectrum

We can tailor our lamps to the desired spectrum or you can use our lamps with adjustable spectrum.

Smart Control

All our lamps can be automatically controlled in terms of intensity and duration.

A note on the light spectrum

Plants do not absorb all wavelengths of light (solar radiation), they are very selective in absorbing the proper wavelength according to their requirements. The most important part of the light spectrum is 400 to 700 nm which is known as photosynthetically active radiation (PAR), this spectral range corresponds to more or less the visible spectrum of the human eye.

The solar radiation spectrum mainly consists of three parts: ultraviolet (UV), visible light, and infra-red.

The following data is quoted from the paper “LEDs for Energy Efficient Greenhouse Lighting”

200-280 nm (ultraviolet C): This part of the spectrum is harmful to the plant. UVC is blocked by the ozone layer, so it does not reach the earth’s surface.
280–315 nm (ultraviolet B): This part is not very harmful but causes plant colors to fade.
315–380 nm (ultraviolet A): This range does not have any positive or negative effect on plant growth.
380–400 nm (ultraviolet A/visible light): Beginning of visible light spectrum, process of light absorption by plant pigments (chlorophylls and carotenoids) begins.
400–520 nm (visible light): Contains violet and blue. Peak absorption by chlorophylls occurs in this range and it has a strong influence on vegetative growth and photosynthesis.

520–610 nm (visible light): This range contains green, yellow and orange bands. This range is less absorbed by the plant pigments and has less influence on vegetative growth and photosynthesis.
610–720 nm (visible light): Contains red bands and a large amount of absorption occurs at this range. This band strongly affects the vegetative growth, photosynthesis, flowering and budding.
720–1000 nm (far-red/infrared): Germination and flowering is influenced by this range but little absorption occurs at this band.
>1000 nm (infrared): All absorption in this region is converted to heat.

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