PHOTOMORPHOGENESIS, PHOTOSYNTHESIS, AND SEED YIELD OF WHEAT PLANTS GROWN UNDER RED LIGHT-EMITTING-DIODES (LEDS) WITH AND WITHOUT SUPPLEMENTAL BLUE LIGHTING

Red light-emitting diodes (LEDs) are a potential light source for grow ing plants in spaceflight systems because of their safety, small mass and volume, wavelength specificity, and longevity. Despite these attra ctive features, red LEDs must satisfy requirements for plant photosynt hesis and photomorphogenesis for successful growth and seed yield. To determine the influence of gallium aluminium arsenide (GaAlAs) red LED s on wheat photomorphogenesis, photosynthesis, and seed yield, wheat ( Triticum aestivum L,, cv. 'USU-Super Dwarf') plants were grown under r ed LEDs and compared to plants grown under daylight fluorescent (white ) lamps and red LEDs supplemented with either 1% or 10% blue light fro m blue fluorescent (BF) lamps. Compared to white light-grown plants, w heat grown under red LEDs alone demonstrated less main culm developmen t during vegetative growth through preanthesis, while showing a longer flag leaf at 40 DAP and greater main culm length at final harvest (70 DAP). As supplemental BF light was increased with red LEDs, shoot dry matter and net leaf photosynthesis rate increased. At final harvest, wheat grown under red LEDs alone displayed fewer subtillers and a lowe r seed yield compared to plants grown under white light. Wheat grown u nder red LEDs + 10% BF light had comparable shoot dry matter accumulat ion and seed yield relative to wheat grown under white light, These re sults indicate that wheat can complete its life cycle under red LEDs a lone, but larger plants and greater amounts of seed are produced in th e presence of red LEDs supplemented with a quantity of blue light.