Photosynthetic Active Radiation (PAR)

Homegrown PotCast
September 02, 2020

On this week’s PotCast, Derek tackles PAR – Photosynthetic Active Radiation. Don’t know what PAR is? PAR is the precise spectrum of wavelengths found in the light that enables photosynthesis. Or put even more simply, it is the amount of light a plant can absorb and convert into chemical energy for sustenance.

Photosynthesis is vital to the growth cycle of cannabis plants, without it, the plants would not be able to sustain themselves – that is why having the correct light available for your marijuana plants is very important.

The spectral range for photosynthesis falls between 400-700 nanometers which can be converted from light energy to chemical energy by plants. There are two types of photosynthesis, the more common oxygenic photosynthesis and anoxygenic photosynthesis, which will perhaps be a little unfamiliar.

What Is Oxygenic Photosynthesis?

During oxygenic photosynthesis, the cannabis plant uses light energy to transfer electrons from water to carbon dioxide to create carbohydrates. As CO2 receives electrons, H2O becomes oxidized and loses electrons – this reaction then creates oxygen alongside carbohydrates for the plant. Oxygenic photosynthesis is essential and plays a role similar to breathing for plants.

What Is Anoxygenic Photosynthesis?

Anoxygenic photosynthesis generally occurs more so in types of aquatic bacteria. This process does not produce oxygen and the byproducts largely depend on the electron donor but typically this would be solid sulfur byproducts.

Why PAR Is Important To The Growth Of Your Cannabis Plants

PAR is a measure of how much light is active in a direct spot or location which can be absorbed by your marijuana plants to trigger photosynthesis. When it comes to growing cannabis, having a higher PAR reading for your lights is actually very important. As well as PAR readings, Photosynthetic Photon Flux Density (PPFD) readings are a way to measure light density in a given area. The amount of light should change depending on the growth stage your plants are in as Derek explains in detail in the PotCast.

Managing your light intensity is crucial to your marijuana plants, knowing the correct PAR and PPFD values required for the cannabis seeds you wish to grow should help to inform your decision when purchasing grow lights.

Homegrown Cannabis Co. is dedicated to providing its customers with as much knowledge about growing marijuana as possible. As always, Derek does a fantastic grow of explaining all of the details pertaining to PAR, photosynthesis in general, and also finding the perfect lights.

If you have any questions regarding this week’s PotCast or about growing in general, Derek is a moderator over at the Homegrown Forum where he is always happy to give advice or have a chat about all things related to cannabis growing.