Increasing energy in the PAR range increases plant photosynthesis, (the plant’s most basic metabolic process). Each crop species has an optimal light intensity that maximizes photosynthesis and plant growth. When there is not enough light, growth and crop quality can decline; and if there is excessive light, photosynthesis and growth will not increase despite the expense of keeping the lights on.
The most common units for measuring light are the foot-candle (primarily in the United States) and lux (primarily in Europe). It is important for growers to understand the limitations of these units. Both units provide an instantaneous light intensity at the time the reading is taken. As we all know, natural light levels are continuously changing and a single measurement in time does not accurately represent the amount of light a plant has received in a day.
Just as important, foot-candles are “photometric” units based on the amount of visible light de- tected by the human eye (primarily green light). That means foot-candles are focused on people and not appropriate for indicating plant photosynthesis.
Most horticultural researchers measure instantaneous light in micromoles (μmol) per square meter (m-2) per second (s-1), or: μmol·m-2·s-1 of PAR. This “quantum” unit quantifies the number of photons (individual particles of energy) used in photosynthesis that fall on a square meter (10.8 square feet) every second. However, this light measurement also is an instantaneous reading.
Daily light integral (DLI) is the amount of PAR received each day as a function of light intensity (instantaneous light: μmol·m-2·s-1) and duration (day). It is expressed as moles of light (mol) per square meter (m-2) per day (d-1), or: mol·m-2·d-1 (moles per day).
The DLI concept is like a rain gauge.
DLI is an important variable to measure in every greenhouse because it influences plant growth, de- velopment, yield, and quality. For example, DLI can influence the root and shoot growth of seedlings and cuttings, finish plant quality (characteristics such as branching, flower number and stem thickness), and timing. Commercial growers who routinely monitor and record the DLI received by their crops can easily determine when they need supplemental lighting or retractable shade curtains.
For green plants the lighting peaks that are most important:
Chlorophyll-a: 430nm/662nm
Chlorophyll-b: 453nm/642nm
Carotenoids: 449nm/475nm
Red pigmented plants use more light in the blue area of the spectrum.
FOR YOU CFL AND FLOURO USERS:
Natural sunshine is 100 CRI & 5300K at peak
Vegging CFL Bulbs
BlueMax Full Spectrum HD CFL Bulbs: 5500k, CRI 93+
BlueMax Full Spectrum HD CFL Bulbs: 5900k, CRI 93+
Indoor Sunshine Full Spectrum CFL Bulbs: 5300k, CRI 95
Duro-Test Color Classer 75: 7500k, CRI 93
Duro-Test Daylight 65: 6500k, CRI 92
Duro-Test Vita-Lite: 5500k, CRI 91
Duro-Test Vita-Lite Plus: 5500k, CRI 91 (higher lumens)
Duro-Test Optima 50: 5000k, CRI 91
Duro-Test Color-Matcher 50: 5000k, CRI 90
NaturesSunlite: 5000k, CRI 85
NaturesSunlite: 6500k, CRI 85
NaturesSunlite Full Spectrum: 5500k, CRI 93
Vegging Fluorescent Tubes
Sylvania Gro-Lux GRO/AQ (these dont have specs, but are great for growing)
Sylvania Gro-Lux Wide Spectrum: 3400k, CRI 89
Verilux Tru-Bloom Full Spectrum: 6280k, CRI 94.5
AgroSun Full Spectrum: 5850, CRI 93
BlueMax Full Spectrum HD: 5900k, CRI 93+
BlueMax Maxum: 5000k, CRI 91+
BlueMax Prolume: 6500k, CRI 91
BlueMax Spectra: 5500k, 5600k, 5900k, CRI 93
Duro-Test Vita-Lite: 5500k, CRI 91
NaturesSunlite: 5500k, CRI 93
NaturesSunlite: 5500k, CRI 96
