Led Grow LED Grow Light Spectrum & Light Science 1

Question 1

Which wavelength range is primarily responsible for vegetative growth in plants under LED grow lights?

Accepted Answer

400-500 nm (blue)

Answer

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?

Accepted Answer

R:FR ratio

Answer

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?

Accepted Answer

Photosynthetically Active Radiation

Answer

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?

Accepted Answer

Red (660 nm)

Answer

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?

Accepted Answer

PPFD

Answer

PPFD (Photosynthetic Photon Flux Density) measures the number of photons hitting a surface per second per square meter.

Led Grow Practice Test