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Light: Difference between revisions
→Upper limit of light intensity: reference for co2 photosynthesis limit
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Once a plant moves into the vegetative stage the maximum light intensity it can tolerate will be 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 in the grower's ability to control the environment.
=== Optimum light intensity===
In this instance, "optimum light intensity" refers to the amount of light that provides the maximum yield from the cultivar.
The threshold for optimal growth and photosynthesis, from the vegetative stage, is
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>
Temperature and light optima for photosynthesis were concluded to be at 25–30 °C and ∼1500 μmol
=== Upper limit of light intensity ===
The theoretical upper limit that a plant can tolerate before experiencing symptoms of poor health.
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▼
▲The 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. Above 500 μmol/s supplemental co<sub>2</sub> is required,<ref>Fluence Cannabis Cultivation Guide, 2020 - https://fluence.science/guides/cannabis-cultivation-guide/</ref> without it more intense light level will harm the plant.
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>
== Measuring light intensity ==
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