Light source spectrum influences long-term flowering cycles and visual appearance in African violet (Saintpaulia ionantha Wendl.)

Light-emitting diodes (LEDs) offer the potential for physiological control of flowering and vegetative growth of ornamental potted plants such as African violet (Saintpaulia ionantha Wendl.). In this experiment, we investigated the flowering and vegetative traits of African violet under 6 months of artificial illumination of four different spectra: monochromatic red, monochromatic blue, mixed red 75% plus blue 25%, and fluorescent light under 118 & mu;mol m(-2) s(-1) & PLUSMN; 6 & mu;mol m(-2) s(-1) photon flux for 12 h per day. Results showed that the number of days to the open flower stage was significantly influenced by irradiance. Although the blue-illuminated plants appeared to be significantly smaller and compact, they were superior in their most flowering qualities as they induced a pronounced effect on the flowering in terms of earliness, uniformity, consistency, the number of flowers, and the percentage of canopy covered with the flowers. We concluded that LEDs can be used as an effective tool to manipulate plant visual qualities without any further need for the application of conventional plant regulator chemicals, which are mostly identified as hazardous substances.