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Light: Difference between revisions
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It is a good idea to match the light schedule with the cultivar's [[Plant_processes#Circadian_rhythm| circadian rhythm]]; I recommend 20/4 or 22/2.
== Ideal light
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
Flowering | 600 - 2000
Once a plant moves into the vegetative stage the maximum light it can tolerate will be limited by other conditions such as CO2 level or nutrient deficiency.
Above (500?) μmol/s supplemental co2 is required [citation required]
=== Optimum light intensity===
Maximum ppfd cannabis can tolerate is around 2000 - 2500 μmol/s in perfect conditions<ref> Light dependence of photosynthesis and water vapor exchange... (Chandra, 2015)- https://doi.org/10.1016/j.jarmap.2015.03.002</ref><ref> Cannabis business times Oct, 2021 https://www.cannabisbusinesstimes.com/article/growing-under-high-light-intensities-lighting-report/</ref> and a DLI of around 40 - 60 moles▼
In this instance, "optimum light intensity" refers to the amount of light that provides the maximum yield from the cultivar. There is a theoretical upper limit that a plant can tolerate before experiencing symptoms of poor health and also a light intensity that is the most energy-efficient for a cultivar, this section is not about exploring those values.
Yield is 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>
Temperature and light optima for photosynthesis were concluded to be at 25–30 °C and ∼1500 μmol m−2s−1 respectively<ref> Photosynthetic response of Cannabis sativa L. to variations in photosynthetic photon flux densities, temperature and CO2 conditions (Chandra, 2008) https://dx.doi.org/10.1007%2Fs12298-008-0027-x</ref>
=== Upper limit of light intensity ===
▲Maximum ppfd cannabis can tolerate is around 2000 - 2500 μmol/s in perfect conditions<ref> Light dependence of photosynthesis and water vapor exchange... (Chandra, 2015)- https://doi.org/10.1016/j.jarmap.2015.03.002</ref><ref> Cannabis business times Oct, 2021 https://www.cannabisbusinesstimes.com/article/growing-under-high-light-intensities-lighting-report/</ref> and a DLI of around 40 - 60 moles
Meta-analysis of plant morphology to light intensity<ref>A meta-analysis of plant responses to light intensity for 70 traits ranging from molecules to whole plant performance (Poorter, 2019) https://nph.onlinelibrary.wiley.com/doi/10.1111/nph.15754</ref>
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