Physicochemical properties and bioactive compounds of purple rice (Oryza sativa L.) seedlings grown under light-emitting diodes

Importance of the work: There has been increasing interest in using light-emitting diodes (LEDs) to aid in the development of bioactive compounds in a variety of plants to enhance crop nutritional quality. Objectives: To investigate the effects of LEDs on the physicochemical properties and bioactive compounds of rice seedlings. Materials & Methods: Purple rice seeds of Oryza sativa L. were grown under LEDs at different wavelengths (white, red, blue, and red+blue LEDs) for 12 hr/d, while the other 12 hr were in darkness. The physical properties, chemical properties and free-radical scavenging activity of the purple rice seedlings were investigated. Results: Applying exposure to LEDs during the seedling stage significantly (p < 0.05) affected the growth and physicochemical quality of the rice seedlings. Seedlings grown under the red LEDs developed an increased plant height and reducing sugar accumulation. The leaf width, total soluble solids content, chlorophyll content (22.70 mg/g), total phenolic content (5.73 mg gallic acid equivalents/g), and free-radical scavenging activity (79.41%) were significantly higher in rice seedlings grown under the blue LEDs than those under the other LED conditions. The red, blue and red+blue LEDs had no significant effects on the hue angle, ascorbic acid content, titratable acidity or pH. Main finding: Blue LEDs can be considered as an abiotic elicitor for growing purple rice seedlings, with the advantage of an increase in the secondary metabolites.