Physiological responses of pepper seedlings to various ratios of blue, green, and red light using LED lamps

Chlorophyll absorbs green light less efficiently than it absorbs other wavelengths in the visible spectrum so green light drives photosynthesis less efficaciously. Green light emitting diodes (LEDs) are also less efficacious at converting electrical energy into photons than their red and blue counterparts. Consequently, most photosynthetic LED lighting has been designed without including green wavelengths in the spectrum. Plant physiological research has largely focused on light signal responses to red, far-red and blue light, but recent efforts suggest other wavebands may play an important role in plant development and photosynthetic activity. We have examined the role of monochromatic red, blue and green light and combinations of these colors with regard to seedling growth of bell pepper. The shoots of pepper plants grown under monochromatic green light had greater leaf area and lower specific leaf weight (mg cm(-2)) than those grown under monochromatic blue or red light. Green light also resulted in taller plants with greater dry weight and thicker stems relative to plants grown with blue light. A broad spectrum including red, green, and blue wavelengths resulted in the highest shoot dry weight and plant compactness.