Supplemental, end-of-day, and sole-source lighting from light-emitting diodes influences growth, morphology, and quality of annual bedding plant seedlings

Randall, Wesley C. M.S., Purdue University, August 2014. Supplemental, end-of-day, and sole-source lighting from light-emitting diodes influences growth, morphology, and quality of annual bedding plant seedlings. Major Professor: Roberto G. Lopez. Annual bedding plants make up the largest sector of the U.S. floriculture industry. Highquality annual bedding plant seedlings are compact, fully rooted transplants with a large stem caliper and high root dry mass. However, production usually occurs in late winter or early spring when the daily light integral (DLI) is as low as 1 to 5 mol∙m∙d in northern latitudes. Therefore, supplemental lighting (SL) is often used to increase the DLI to a recommended 10 to 12 mol∙m∙d. The objectives of this study were to: 1) quantify the effects of SL from three light-emitting diode (LED) sources of different light qualities and high-pressure sodium (HPS) lamps; 2) quantify the effects of end-of-day (EOD) light from incandescent and compact fluorescent lamps, LEDs of low, medium, and high red:far-red light ratios, or mixed red:blue:far-red ratios (Expt. 2); and 3) quantify the effects of ambient light and SL from LEDs, HPS, and plasma (PL) lamps in a greenhouse, and the effects of sole-source light (SS) from LEDs with two different light qualities in a growth chamber vertical production system (Expt. 3) on seedling growth, morphology, quality, and subsequent flowering. Supplemental light proportions (%) from LEDs (Expt. 1 and 3) ranged from 100:0 to 70:30 red:blue light, and EOD (Expt. 2) LED light