A first set of orange LEDs with a peak wavelength emission of about 612 nanometers,
a second set of red light emitting LEDs with a peak wavelength of about 660 nanometers,
and blue light LEDs. Two beam spreads, 15 and 30, were provided for
both the 660 nm LEDs and 612 nm LEDs. When directed perpendicularly upon tops of
the plant leaves, 10% light transmission occurred through the leaves for the 30
LEDs, and 80% light transmission for the 15 LEDs. Thus, fully 50% of the
orange/red spectrum primarily used for photosynthesis was transmitted through the
upper leaf canopy, making it available to support photosynthesis in leaves below.
LED lamps are positioned at varying distances from the growing plants for controlling
plant growth rates that vary with these distances, thereby to control plant inventory,
because growth of plants can be greatly slowed to preserve them during periods
of slow sales.
