As a grower, when you come to purchase an LED grow light, you will confront several confusing abbreviations which always followed by some figures and are implemented to describe the product. These abbreviations ---PAR, PPF and PPFD play an important role for us to understand the LED grow lights that we interested in. Therefore, acknowledge what these acronyms mean and what they stand for will greatly help you to buy an ideal light.
What is PAR?
PAR is the abbreviation of photosynthetic active radiation. According to the full name, we will find this term relates to the portion of the useful light from the illumination source and is always used to describe the visible light range of 400~700nm. When it is applied in LED grow light, it usually stands for how strength the spectrum from the grow light is and the portion of the light spectrum utilized by plants for photosynthesis.
A common misconception about the PAR is higher value it is, better yields it will bring. In fact, how many PAR your plants need is depend on their variety. For instance, the best PAR for cannabis ranges from 600 to 900µMol/m2/S. If the PAR value over this range, the photosynthetic efficiency of your plants will decline simultaneously. Hence, whether the PAR value of lower or higher than this range will impact the cannabis’s growing condition and harvest quantity.
What is PPFD?
PPFD, photosynthetic photon flux density, is a measurement of how much useful light actually hitting the plant in a given area every second. Its value is measured in micromoles per square meter per second(900µMol/m2/S).
Through the definition of photosynthetic photon flux density, you may already discovered the relationship between PPFD and PAR ----the former one measures how much PAR there is.
As PAR, your cannabis plants also have their favorite PPFD range. For regular weed growing, the PPFD for seedling stage is 100-300µmol/m²/s; the PPFD for vegetation stage is 400-600µmol/m²/s, and the PPFD for flowering stage is 800-1,000µmol/m²/s. Furthermore, according to the article published on NIH, the cannabis’ dry inflorescence yield increased linearly with increasing canopy-level PPFD up to 1,800 μmol·m−2·s−1, while leaf-level photosynthesis saturated well-below 1,800 μmol·m−2·s−1. Growers can select an LED grow lights that perfectly meet the needs of their plants according to the data.
