Towards efficient conversion of electricity into edible biomass in crop production systems: a transgenic approach

A major problem of controlled environment crop production is the procurement and distribution of adequate light for plant growth. Some electrically efficient light sources lack specific wavelengths required for photomorphogenesis yet provide a light spectrum with a high potential photosynthetic yield. To enable use of these lamps, we describe a concept to genetically modify plants to change their morphogenic responses to light. Photoreceptors in the red and far-red light sensing phytochrome family and the blue light sensing cryptochrome family may be useful to increase or decrease plant sensitivity to regions of the photomorphogenic spectrum. Uses of developmental masterswitches such as COP and DET, and downstream developmental controls, such as the cytokinin biosynthesis enzyme isopentenyl transferase, are also detailed. If photomorphogenic needs can be altered, then lamp selection can be based solely on electrical efficiency of light production and on potential photosynthetic yield from light produced. The combination of lamp electrical efficiency and photosynthetic yield, termed photosynthetic efficacy, was calculated for plant lighting sources. The low-pressure sodium (LPS) and high-pressure sodium (HPS) lamps provide the highest photosynthetic efficacies relative to microwave, metal halide, red and blue light-emitting diodes (LED), and fluorescent lamps. Typically plants grow tall and spindly under LPS or red LED irradiation and in some cases under the broader spectrum of HPS. The strategy of genetic modification of plant light requirements may enable use of electrically efficient and photosynthetically useful red-biased light sources without supplementation from less electrically efficient blue or less photosynthetically useful far-red light sources.