This document provides definitions for key terms used in horticultural lighting.
These terms relate to the basic concepts of light and plant growth.
The total amount of photosynthetically active photons (400-700 nm) emitted by a lighting system per second. Measured in micromoles per second (μmol/s).
The density of photosynthetically active photons arriving at a specific surface (e.g., the plant canopy) per second. Measured in micromoles per square meter per second (μmol/m²/s).
These terms describe the quality and composition of light.
The ratio of photosynthetic photon flux (PPF) to the input electrical power. Measured in micromoles per joule (μmol/J). Indicates the energy efficiency of a horticultural light.
The density of photons within a specific waveband arriving at a surface per second. Often used for wavebands outside the traditional photosynthetic range (e.g., far-red).
Terms related to the practical use and installation of lighting systems.
The cumulative amount of photosynthetically active photons delivered to a specific area over a 24-hour period. Measured in moles per square meter per day (mol/m²/d).
The ratio of the total photosynthetic photon flux (PPF) emitted by a luminaire to its input power. Measured in μmol/J. A key metric for evaluating fixture energy performance.
Understanding these terms is essential for evaluating horticultural lighting systems and their impact on plant growth and energy use.
