title: Characterizations of high-intensity red and blue light-emitting diodes (LEDs) as a light source for plant growth.
abstract: Recently developed high-intensity red and blue light-emitting diodes (LEDs), which constitute a potentially improved light source for controlled-environment plant growth applications such as in vitro micropropagation and biologically based advanced life support (ALS) for space missions, were characterized in this study. Blue 2 LED and Red 1 LED consistently yielded the highest and lowest voltage drop readings, respectively, for all the electrical current settings tested (5-50 mA), with Blue 1 LED producing voltage drops falling nearly in the middle of the readings for the first two LEDs. At the standard current setting of 20 mA, Blue 2 LED and Blue 1 LED required 2.5 and 1.6 times more electrical power, respectively, than did Red 1 LED. At the standard current of 20 mA, the average photosynthetic photon flux (PPF) for Red 1 LED, Blue 1 LED, and Blue 2 LED were 180, 145, and 36 micromoles m-2 s-1, respectively. Red 1 LED peaked at 460 micromoles m-2 s-1 at 50 mA, Blue 1 LED at 200 micromoles m-2 s-1 at 40 mA, and Blue 2 LED at 40 micromoles m-2 s-1 at about 25 mA. For all current settings, the electrical conversion efficiency of Red 1 was approximately two times greater than that of Blue 1 LED. The electrical conversion efficiency of Blue 1 and of Red 1 LED peaked in between 10 and 20 mA, at about 13 mA for Blue 1 LED and at about 15 mA for Red 1 LED. The normalized PPF distributions for both Red 1 LED and Blue 1 LED were independent of the various magnitudes of electrical current (20, 30, 40, and 50 mA) that were applied to the LEDs.
authors.affiliation: Department of Agricultural and Biosystems Engineering, The University of Arizona, Tucson, AZ 85721, USA. eiichi@u.arizona.edu
authors.forename: E
authors.initials: E
authors.lastname: Ono
authors.forename: J L
authors.initials: JL
authors.lastname: Cuello
authors.forename: K A
authors.initials: KA
authors.lastname: Jordan
mesh_terms: D018504:Ecological Systems, Closed; D004560:Electricity; D005069:Evaluation Studies as Topic; D008021:Life Support Systems / Q000295:instrumentation*; D008027:Light; D008029:Lighting / Q000295:instrumentation*; D017785:Photons; D063245:Plant Development; D010944:Plants / Q000528:radiation effects