Led Grow Plant Growth Stages & LED Lighting 1

Question 1

What light schedule is typically used to keep cannabis plants in the vegetative stage indoors?

Accepted Answer

18 hours light / 6 hours dark

Answer

An 18/6 light schedule (18 hours on, 6 hours off) is the most common schedule for keeping photoperiod cannabis in the vegetative stage.

Question 2

What light schedule is required to trigger flowering in photoperiod cannabis strains?

Accepted Answer

12 hours light / 12 hours dark

Answer

A 12/12 light schedule signals photoperiod cannabis to transition into flowering by mimicking the shorter days of late summer.

Question 3

What PPFD level is generally recommended for cannabis seedlings in their first two weeks?

Accepted Answer

50-150 µmol/m²/s

Answer

Cannabis seedlings require very low PPFD (50-150 µmol/m²/s) as their underdeveloped roots and leaves cannot handle intense light.

Question 4

How does increasing CO2 concentration above ambient levels (1500+ ppm) benefit plants under high-intensity LED grow lights?

Accepted Answer

It allows plants to photosynthesize at higher light intensities without reaching light saturation

Answer

Elevated CO2 raises the light saturation point, allowing plants to utilize higher PPFD levels (1500+ µmol/m²/s) for increased photosynthesis and yield.

Question 5

What is 'light burn' in cannabis plants, and what causes it under LED grow lights?

Accepted Answer

Bleaching and necrosis of upper leaves caused by excessive PPFD from lights too close

Answer

Light burn occurs when LED fixtures are too close to the canopy, delivering excessive PPFD that bleaches and damages upper leaves.

Led Grow Practice Test

Led Grow Practice Test

Led Grow Plant Growth Stages & LED Lighting 1