Photon Red 660nm 0.5W 1W 2835 SMD LED Chip

Related Knowledge provided by GMKJ LEDs

Why 660nm photon red is the key wavelength for horticulture plant growth lights?

660 nm (deep red) is considered the "key wavelength" in horticulture lighting because it strongly matches how plants use light in photosynthesis and flowering regulation.

1. Photosynthetic efficiency

Plants absorb light mainly via chlorophyll a & b.

Both pigments have strong absorption peaks in the red region (≈640–680 nm), with the deep red ~660 nm giving the highest photon absorption efficiency.

This means photons at 660 nm are converted into chemical energy more effectively than most other visible wavelengths.
👉 So per photon, 660 nm contributes more to photosynthesis (high quantum yield).

2. PAR & PPF weighting

PAR (Photosynthetically Active Radiation) = 400–700 nm.

Within PAR, the McCree curve (plant photosynthetic action spectrum) shows a peak in the red ~660 nm.

Grow-light makers choose 660 nm LEDs because each watt of electrical input → many usable PPF photons for plants.

3. Photomorphogenesis (plant development signals)

Beyond photosynthesis, phytochromes (plant photoreceptors) sense red & far-red light.

660 nm excites the "Pfr" form of phytochrome, which regulates:

Seed germination

Stem elongation inhibition

Leaf expansion

Flowering induction in many species

By combining 660 nm red with 730 nm far-red, growers can manipulate photoperiod, flowering time, and plant morphology.

4. Why not just 630 nm (bright red)?

630 nm (orange-red) also drives photosynthesis, but its absorption efficiency is lower than 660 nm.

Studies and LED grow-light trials consistently show 660 nm delivers higher biomass and flowering efficiency per unit energy.

That's why 660 nm "deep red" LEDs are the industry standard.

✅ Summary:
660 nm photons hit the sweet spot of plant absorption + phytochrome activation, giving maximum photosynthesis efficiency and strong influence on flowering and morphology. That's why horticulture LEDs almost always include deep red 660 nm as the "key wavelength," often combined with blue (~450 nm) and sometimes far-red (~730 nm) to balance growth and structure.