About the concept of plant lighting

Plant lighting is a technology and concept that uses artificial light to promote plant growth. LED lighting, which is ideal for plants and close to natural light, is being developed and researched in collaboration with industry, government, and academia. It is also used by companies for indoor cultivation, plant factories, greenhouses, etc. When it comes to plant lighting, the following three points are important when it comes to lighting equipment.

1. Basic Elements of Light

There are three main factors that affect plant growth:

① Wavelength of light (spectrum)

　　Plants use light of specific wavelengths for photosynthesis.

　　Blue light (approx. 400-500nm) → Promotes leaf growth and makes plants compact

　　Red light (approx. 600-700nm) → Promotes flowering and fruit growth

　　Green light (approx. 500-600nm) → Less efficient for plants, but delivers light to

　　deeper parts

　　Recently, full-spectrum LEDs optimized for specific wavelengths have been

　　 developed, allowing you to create an environment closer to natural light.

② Light Intensity (PPFD: Photosynthetic Photon Flux Density)

　　PPFD (Photosynthetic Photon Flux Density) is an index (μmol/m²/s) that indicates the

　　 amount of light that plants can use for photosynthesis.

　　The appropriate light intensity varies depending on the type of plant.

　　Shade-loving plants (foliage plants): 50-200 PPFD

　　Vegetables (lettuce, etc.): 200-400 PPFD

　　Fruit vegetables such as tomatoes and strawberries: 400-800 PPFD

　　These are considered guidelines.

*By the way, what is PPFD (Photosynthetic Photon Flux Density)?

PPFD (Photosynthetic Photon Flux Density) is an index that

 shows the intensity of light that plants can use for

 photosynthesis.

Unit: μmol/m²/s (micromoles per square meter per second)

It refers to the number of photosynthetically active radiation (PAR: light between 400 and 700 nm) photons that a plant receives per second.

The importance of PPFD is that if PPFD is too high, leaves will burn, and if it is too low, growth will be retarded. The ideal PPFD value varies depending on the type of plant.

③ Photoperiod

　　The amount of time a plant is exposed to light (photoperiod) is also important for

　　 plant growth.　Short-day plants (flower bud formation is promoted by short days):

　　 cosmos, poinsettia

　　Long-day plants (flower bud formation by long hours of sunlight): lettuce, spinach

　　Neutral plants (not easily affected by photoperiod): tomatoes, cucumbers, etc.

　　Normally, 12 to 16 hours of light is considered suitable for plant growth.

When using plant lighting, it is important to consider the following:

✅ Appropriate wavelength (blue/red)

✅ Appropriate light intensity (PPFD)

✅ Appropriate photoperiod (12-16 hours)

The optimal light conditions vary depending on the type of plant you want to grow, so the key is to choose a lighting fixture that matches those conditions.

The ideal light wavelengths for plant lighting are mainly concentrated in two ranges:

Characteristics of each wavelength

1. Blue light (approx. 400-500 nm)

Main wavelength: approx. 450 nm

　●　Promotes photosynthesis (high chlorophyll

　　　 absorption)

　●　Promotes growth of plant leaves and stems (compact and healthy growth)

　●　Regulates stomata (controls transpiration)

2. Red light (approx. 600-700nm)

Main wavelength: approx. 660nm

　●　Improves photosynthesis efficiency (especially well absorbed by chlorophyll A)

　●　Promotes flower and fruit growth

　●　Regulates flowering and germination (affected by photoperiod)

　　　※ Supplementary wavelength

Green light (approx. 500-600nm)

 → Low absorption rate for plants, but reaches deep into the leaves and assists

　 photosynthesis

Far-red light (approx. 700-750nm) 

→ Promotes flowering induction and elongation (elongation of stems)

      Composed of

Ideal light balance

Blue light: Approximately 20-30%

Red light: Approximately 60-70%

Other (green and far-red): 10% or less

Recently, full-spectrum LEDs can provide a balance

 close to natural light, creating a more ideal lighting environment.

It is more effective to adjust the light ratio according to the plants you want to grow.

Some plants grow faster under green light than under blue light, and other plants have different characteristics for growth and photosynthesis

in relation to the wavelength and color temperature, but the running costs, such as electricity and maintenance costs

will also be important points for future development and research, and how they are used will also be a key point.