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Plant Light Requirements

Jul. 16, 2019

The specific needs of plants determine which lighting is best for optimal growth, and artificial light must mimic the natural light that plants best fit. If a plant does not get enough light, it will not grow, regardless of other conditions. For example, vegetables grow best in full sunlight and thrive indoors, they need the same high light levels, and leaf plants (such as velvet) grow in the shade and can grow at a lower level of normal light.

The way in which plant lights are used depends on the stage of plant growth. In general, it is recommended that the plants receive 16 hours of rest during the seedling/growth phase, 8 hours of rest; the vegetative stage receives 18 hours of rest, 6 hours of rest; and the flowering stage receives 12 hours and 12 hours of rest.


In addition, many plants also require darkness and photoperiod, an effect known as the photoperiod to trigger flowering. Therefore, the switch can turn the light on or off at the set time. The optimal ratio of photoperiods depends on the type and type of plant, as some prefer long and short nights, while others prefer opposite or medium lengths.

When discussing plant development, the photoperiod is highly valued.

Plants that respond to photoperiod may have a facultative or specific response. A part-time reaction means that a plant will eventually spend light, regardless of how the photoperiod grows faster at a particular photoperiod. Professional response means that plants can only be grown if they are grown under certain light conditions.

Photosynthetically active radiation (PAR)

Usually used to measure the brightness and lumens of light, but they are metric units that measure the intensity of light perceived by the human eye.

The spectral level of light that can be used for photosynthesis is similar to, but not identical to, measured by lumens. Therefore, when measuring the amount of light in plant photosynthesis, biologists typically measure the amount of photosynthetically active radiation (PAR) that plants receive. PAR represents the spectral range of solar radiation from 400 to 700 nanometers, which generally corresponds to the spectral range that photosynthetic organisms can use during photosynthesis.

The irradiance of PAR can be expressed in terms of energy flux (W/m2), which is related to the energy balance considerations of photosynthetic organisms. However, photosynthesis is a quantum process, and the chemical reactions of photosynthesis depend more on the number of photons than on the amount of energy contained in photons. Therefore, plant biologists typically quantify the number of PARs using the number of spectra or photosynthetic photon density (PPFD) received over a specified period of time. This is usually measured using −2s−1.

According to a manufacturer of growth lamps, plants need a light level of at least 100 to 800 μmol m−2s−1. For daylight spectroscopy (5800 K), this photosynthetically active radiation will be equivalent to 5800 to 46,000 lm/m2.

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