Light spectrum refers to the distribution of wavelengths emitted by a grow light source. Different wavelengths within the PAR range (400β700 nm) affect plant growth differently: blue wavelengths (400β500 nm) promote compact vegetative growth, red wavelengths (600β700 nm) drive photosynthesis and flowering, and far-red wavelengths (700β800 nm) influence stem extension and the shade avoidance response. Full-spectrum LEDs attempt to approximate natural sunlight by combining multiple wavelengths.
Key Facts
- Blue (400β500 nm): compact growth, thick leaves, strong root development
- Red (600β700 nm): peak photosynthetic efficiency, flowering trigger (short-day plants)
- Far-red (700β800 nm): stretching, canopy penetration, Emerson enhancement effect
- Green (500β600 nm): partially used by plants; penetrates deeper than red/blue
- Full-spectrum LEDs mimic natural sunlight; white LEDs use phosphor conversion
- Red:Blue ratio affects plant morphology β higher blue = more compact plants