Led Grow LED Grow Light Spectrum & Light Science 1 — Questions and Answers
Question 1: Which wavelength range is primarily responsible for vegetative growth in plants under LED grow lights?
- 400-500 nm (blue) (Correct answer)
- 500-600 nm (green)
- 600-700 nm (red)
- 700-800 nm (far-red)
Correct answer: 400-500 nm (blue)
Blue light in the 400-500 nm range drives vegetative growth by promoting compact, leafy development.
Question 2: What is the term for the ratio of red to far-red light that influences plant flowering?
- PAR ratio
- R:FR ratio (Correct answer)
- PPFD index
- Lux coefficient
Correct answer: R:FR ratio
The R:FR (red to far-red) ratio signals plants to trigger or delay flowering based on light quality.
Question 3: What does PAR stand for in the context of LED grow lighting?
- Plant Absorption Rate
- Photosynthetically Active Radiation (Correct answer)
- Peak Active Response
- Photon Absorption Range
Correct answer: Photosynthetically Active Radiation
PAR stands for Photosynthetically Active Radiation, covering the 400-700 nm range used by plants for photosynthesis.
Question 4: Which color of light is most associated with promoting flowering and fruiting in cannabis under LED grow lights?
- Blue (450 nm)
- Green (530 nm)
- Red (660 nm) (Correct answer)
- UV (380 nm)
Correct answer: Red (660 nm)
Red light at around 660 nm is the most efficient wavelength for driving photosynthesis and promoting flowering.
Question 5: What unit is used to measure the intensity of PAR light delivered to a plant canopy?
- Lux
- Lumens
- PPFD (Correct answer)
- Kelvin
Correct answer: PPFD
PPFD (Photosynthetic Photon Flux Density) measures the number of photons hitting a surface per second per square meter.
Question 6: What is the approximate PPFD range recommended for cannabis plants in the vegetative stage?
- 100-200 µmol/m²/s
- 200-400 µmol/m²/s
- 400-600 µmol/m²/s (Correct answer)
- 800-1200 µmol/m²/s
Correct answer: 400-600 µmol/m²/s
Vegetative cannabis plants typically thrive with PPFD levels between 400-600 µmol/m²/s for healthy growth.
Led Grow LED Grow Light Spectrum & Light Science 1
Which wavelength range is primarily responsible for vegetative growth in plants under LED grow lights?