Cares

What does plant care?

• PAR: photosynthetically active radiation

  Photosynthetically active radiation, also known as PAR, stands for the spectral range of solar radiation from 400nm to 700nm. It defines the light the plant needs to support photosynthesis. In this range, plants’ photosynthetic organisms are able to absorb light in the process of photosynthesis.

• PPF: photosynthetic photon flux

  Photosynthetic photon flux (PPF) is a measurement that determines the total amount of photosynthetic active radiation (PAR) a light gives off. It values all photons from 400nm to 700nm based on plant's photosynthetic response.

• PPFD: photosynthetic photon flux density

  Photosynthetic photon flux density (PPFD) is another measurement that provides the same information as PPF. It also stands for the photons in the spectral range of 400nm to 700nm. While the difference between them is that PPF measures how many photons get off from a light source. On the other hand, PPFD is about how many photons drop on a surface area in square meter.

• DLI: daily light integral

  Daily light integral (DLI) represents the number of PAR that are delivered to a square meter area in a day and night (24 hours). Sometimes, this value also is calculated in second. Generally, 10 and 30 mol·m^-2·d⁻¹.

Recipes

Typical points
of lighting recipes

• Harmful for plants
• Harmful for plants
• Useful for photosynthesis
• Useful for photosynthesis
• More or less useful
• Useful for photosynthesis,
  flowering,budding
• Useful for germination, leaf building, flowering

Generally, 450nm blue and 660nm red light are widely used in horticulture lighting to specifically control the plants' flowering and growth (730nm is also commonly used).

The phytochromes PR and PFR will mainly influence the performance of germination, leave growth and flowering. In order to control the photomorphogenic effects on leaves and flowers, it is necessary to mix 660nm and 730nm with a certain ratio.

Lumen efficacy (lm/w) is a misleading light source, which is a useless reference for horticulture lights as plants are different with human being in radiation energy sensation. High energy efficacy in μmol/J is the correct form of evaluation.

White color LED lights are also necessary for providing a human friendly working environment.

Spectrum

What spectrum
does plant need?

What should be considered prior is about how to maximize yield with less budget.

Therefore, in the aspect of spectrum, we should consider which spectral range is needed for the plant and which part is useless. Keeping a helpful spectral range and getting rid of the excess are the key points of the plant growing spectrum design. Consequently, we are able to optimize the operating factor of electrical energy by transferring electrical energy into useful light.

In the process of plant growing, as we all know, the factors determine the growing performance are Chlorophyll A and Chlorophyll B.

Chlorophyll A will absorb light of red, blue and deep blue, especially the range of blue light from 380nm to 450nm and the range of red light from 600nm to 700nm. From its absorption spectrum, the peak of blue and red ratios in 1:1.

Chlorophyll B will absorb light, alike Chlorophyll A, of red, blue and deep blue. While the useful spectral range is different, which is 400nm-500nm in blue and 600nm-650nm in red. From its absorption spectrum, the peak of blue and red ratios in 3:2.

• Chlorophyll A
• Chlorophyll B

Common examples

Common examples of LED
spectrum for different purposes

• 

  Typical supplement lighting solution:

  Blue LEDs (450nm):Red LEDs (660nm) = 1:9

• 

  Typical propagation supplement lighting solution:

  Blue LEDs (450nm):Red LEDs (660nm) = 3:1

• 

  Typical flowering supplement lighting solution:

  Blue LEDs (450nm):Red LEDs (660nm):Far Red LEDs (700nm) = 1:3:1