During photosynthesis,plants use energy inthe re-
gion of the electromagnetic spectrum from 400-
700 nm (1,2). The radiation in this range,referred
to as Photosynthetically Active Radiation (PAR),
can be measured in energy units (watts m-2
) or as
Photosynthetic Photon Flux Density(PPFD),which
has units of quanta (pho-tons) per unit time per
unit surface area.The units most commonly used
are micro-moles of quanta per second per square-
meter (μmol s-1
m-2
). Plant scientists, horticultu-
rists, ecologists,and other environmental scientists
use the LI-190SA Quantum Sensor to accurately
measurethis variable.