What percentage is given by PPF

Light related to plant growth

There are various ways of assessing light. Some of these methods relate to the light that plants can use. We want to take a targeted look at these in this article. Because “Lumen is for human!”. We have two important factors that are unfortunately often misunderstood. On the one hand, there is the quantity of light and the quality of light. In the following we will specifically address the individual terms and explain what is behind them.

Light quantity

The quantity of light, or the amount of light, is the directly correlating factor when it comes to the production of biomass. That means - the more light, the more biomass (up to a certain limit). Since photosynthesis is a quantum process, it can be quantified on a photon basis. In the following we present three ways to measure and test the quantity of light.

PPF (photosynthetic photon flux) - is the unit of measurement that shows the overall performance in the spectrum relevant for plant growth. Here photons are measured that are emitted (ejected) from the source - the information is given in µmol / s. It is a very important factor because it shows the possible output of a light source or luminaire.

Average PPFD (Photosynthetic Photon Flux Density) - The "D" stands for density and indicates how many PPF hit an area of ​​1m². The values ​​for PPFD are given in µmols / m². Studies of different plant species have shown that 700-1000μmols / m² represent an optimal average value for light-intensive plants. Over 1000 µmols / m² are not to be aimed for without additional aids such as Co2.

Direct PPFD values ​​(PAR meter) - Many are familiar with PAR meters and the direct PPFD values ​​that are output by these devices. These are very useful to see how the light is distributed and what value prevails at a certain point. However, a value does not say anything about the light output over the entire area. Therefore, such devices are used to collect data at several points in order to arrive at the average PPFD value in the end.

Light quality

A better known form of light quality is the spectrum. The spectrum is essentially the distribution of light over the different wavelengths that are emitted by a source. The different colors are created by the different energy levels of the photons. The more energetic a photon, the more bluish its color. On the other hand, the lower the energy level, the redder a photon is. When it comes to photosynthesis, color is used to determine the potential effectiveness of light in terms of growth. This was confirmed by Dr. McCree demonstrated in 1972 when he studied and identified 22 different species of plants by their carbon fixation in response to different wavelengths of light. This led to what we know as the McCree Relative Quantum Efficiency Curve or RQE Curve. To date, this is the only scientifically recognized study of the effectiveness of the various wave ranges in relation to plant growth.

It should be noted that, as is often wrongly assumed, only the red and blue areas are important. Although the red and blue wavelength ranges are driving forces in photosynthesis and physiological development, they are not the only useful or necessary wavelengths necessary for maximum physiological development and mass yield. A full and white spectrum is needed for photosynthesis to be maximized and for biological processes to be triggered correctly.

If you look at the 3500K spectrum of the sunflow, which was superimposed here with the McCree RQE curve, you can see the following:

The spectrum of LED chips we use fits the McCree curve perfectly. The white spectrum of the LEDs is a targeted balance of the entire spectrum from 380nm-780nm. The blue wave range increases the production of essential oils and the terpenes. In addition, this results in shorter node distances (nodes = nodes of leaves and branches). The often misunderstood region from green to yellow ensures balanced and healthy plant growth. The orange to red wave range is the driving force in the fruit phase and an important factor in the development of flowers and fruits.

English original version of Pacific Light Concept Thanks and greetings to the States!

Featured image: © Apiwat - stock.adobe.com