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Revision as of 15:01, 10 September 2023

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→‎Ideal light conditions: Correction on low light for seedlings
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(→‎Horticultural light metrics: Cleaned up metrics section)
(→‎Ideal light conditions: Correction on low light for seedlings)
 
== Ideal light conditions ==
Cannabis can tolerate an extreme light intensity. Many growers limit light levels early in the plants life but this is not nessesary<ref>Best Grow Lighting for Cannabis with Dr Bruce Bugbee | Far red ePAR - https://youtu.be/VvBTsl_gScw?si=4kS8z9cSu9hprAMu&t=2771</ref>.
In the initial stages of growth when the plant is a seedling, it should be exposed to much less light than when in flowering. This is for photoacclimation[citation needed].
 
Ideal intensity is around 1000 - 2000 μmol/s
{| class="wikitable"
|+Light over time
|Life stage
|style="text-align:center;" | PPFD
|-
|Seedling
|100 - 400 μmol/s
|-
|Flowering
|600 - 2000 μmol/s
|}
 
Once a plant moves into the vegetative stageGenerally the maximum light intensity ita plant can tolerate will bebecomes limited by other conditions such as CO2 level or nutrient deficiency. Note that light intensity is proportional to the rate of [[Plant processes#Transpiration|transpiration]], meaning higher light intensity can raise the [[Temperature and Humidity|humidity]] of the environment as more water exits the plant. This creates another potential limitation to the maximum light that can be applied; the grower's ability to control the temperature and humidity.
 
=== Optimum light intensity===
The threshold for optimal growth and photosynthesis, from the vegetative stage, is a DLI of 65 moles.<ref> Daily Light Integral DLI Relation To Cannabis Yield (Meta-analysis, Matthew Debacco, 2021) https://www.youtube.com/watch?v=au7G-oVDeKg</ref>
 
Yield appears to be linear with PPFD to around 1500 - 2000 μmol/s<ref>Cannabis Yield, Potency, and Leaf Photosynthesis Respond Differently to Increasing Light Levels in an Indoor Environment (Rodriguez-Morrison, 2021) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8144505/</ref>
<ref>High Light Intensities Can Be Used to Grow Healthy and Robust Cannabis Plants During the Vegetative Stage of Indoor Production (Moher, 2021) https://www.preprints.org/manuscript/202104.0417/v1</ref>
 
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