The higher the wattage, the more electricity your light will use. Theoretically, the higher the wattage, the higher the PAR output. Another lighting term you may see from time to time is photon efficacy. This measures how efficiently a grow light converts electrical energy into PAR. To calculate the photon efficacy of light, you can divide the known PPF by the input wattage of your grow light. The greater the photon efficacy, the more efficient a light is at converting energy into PAR, which means the less expensive it will be to grow plants.
Photobiology is the study of the interaction between light and living organisms. Plants are autotrophs that evolved to use light energy from the sun to make their own food source via photosynthesis. Thus, light is the most critical environmental variable concerning plant growth. Without light, plants cannot survive.
Plants, algae, and some bacteria capture energy from sunlight to produce oxygen (O2) and chemical energy stored in glucose (a sugar). During photosynthesis, plants take in carbon dioxide (CO2) and water (H2O) from the air and soil. Within the plant cell, the water is oxidizing, meaning it loses electrons, while the carbon dioxide is reduced, meaning it gains electrons. This transforms the water into oxygen and the carbon dioxide into glucose. The plant then releases the oxygen back into the air and stores energy with the glucose molecules.
Photosynthetic photon flux (PPF) measures the total amount of PAR that is produced by a lighting system per second (expressed as micromoles per second – μmol/s). PPF measures all the light energy in the PAR range. This metric gives us a great idea of how much usable light a particular grow light is able to emit, but it doesn’t give us the whole picture.
PPFD, or photosynthetic photon flux density, measures how much PAR reaches the plant at any given time (expressed as micromoles per square meter per second – μmol/m2/s). This will help you understand how high to keep your lights above your plants. Fluorescent lights have a lower PPFD than LED or HID, meaning you must keep fluorescents closer to plants. T-8 lights should be 1 inch from the plants, whereas T-5 can be 6 inches to a foot above the plants. Measuring PPFD properly requires multiple readings taken in multiple positions. A single reading only measures a specific location underneath a light source. For example, the PPFD in the center of a grow light’s footprint will always be greater than the PPFD measured two feet from the center, assuming the vertical distance from the light was equal in both readings. Grow lights that only offer a single PPFD reading won’t give you the best idea for PAR uniformity or the realistic max coverage area the light can support. Having as many different readings as possible, both vertically and horizontally, allows for the most accurate PPFD averages. Ideal PPFD depends on plant type and growth phase. A PPFD value of 200-400 is suitable for seedlings or a mother plant, 400-600 for vegetative growth, and 600-900 when you produce flowers/fruit.
Wavelengths of light that drive photosynthesis are primarily found within the 400 – 700nm range. Within a plant leaf are various pigments and photoreceptors that respond to different wavelengths of PAR. These pigments and photoreceptors perceive the intensity of photons that are absorbed, which impacts the rate of photosynthesis and overall plant growth.
In the structure of the female cannabis plant, the pistils are the reproductive organ. The pistils are often confused with stigmas. However, the pistils are the part of the cannabis plant from which the stigmas grow. The pistil is the part where the pollen from the male plant is collected. The pistils have three parts: the stigma, ovary, and style. Over time, the appearance of the pistils and their parts can change colors as the cannabis plant grows.
While not used for photosynthesis, ultraviolet (UV) and infrared (IR) wavelengths of light energy are involved in photobiological reactions in plants, meaning they are essential in plant growth. More advanced growers should know their lights’ UV and IR output. Where PAR covers 400nm-700nm, the visible light spectrum used for photosynthesis, PBAR covers 300nm-800nm, which includes both UV and IR wavelengths. More and more research has been coming out on the benefits of using supplemental UV for increased resin production. Most growers know that red light is needed for a good flowering response. Light in the far red range increases photochromic responses and is involved in flowering. Many studies show that when plants get 660-680, deep red, and 680-730, far red, they show an increased flower production. Manufacturers have responded to the research, and we are starting to see more and more lights including these UV and IR enhancements, as well as specialty lights such as horticultural UV, grow light bulbs, and far red LED strip lights, so it only makes sense that we are starting to hear more about PBAR.
Often referred to as PE tubing or polyethylene tubing is a flexible, lightweight, durable, and corrosion-resistant plastic that can be sued for a wide range of liquid, gas, and fluid transfer applications. Poly tubing is also FDA-approved for use in food and beverage applications.