The many advantages of light-emitting diode (LED) grow lamps in terms of programmability and energy efficiency make them an attractive replacement for old lighting systems. However, when replacing conventional broad-waveband ‘white’ lighting with narrow-waveband LED lighting it is important to ensure that the system is able to produce plants of an equal or higher quality and yield. In order to choose suitable light ‘recipes’, i.e. combinations of wavelengths for optimal plant growth, we must first understand how light quality affects plant growth and development. The following work explores the role of each part of the light spectrum, both in natural sunlight in canopy environments in the field and glasshouse, and in an artificial light environment in controlled environment growth rooms. It was determined that, blue, green, red and far-red wavebands are all instrumental in the provision of positional signals to the leaf which enable optimisation of plant physiology to light conditions, especially in the canopy environment. A new hypothesis for the role of the blue:green light ratio in whole-canopy water use efficiency is presented. Wavelength-specific effects were observed in hypocotyl elongation, leaf expansion, photosynthetic stoichiometry and absorption of different wavelengths, root architecture, photosynthetic capacity, whole-plant morphology (in terms of biomass partitioning between leaves, stems and roots) and fresh weight yield of stems and leaves. In the glasshouse, it was determined that monochromatic red LED lighting is a suitable alternative for conventional high-pressure sodium light, as it boosted leaf photosynthetic capacity as well as leaf area, fresh and dry weight yield, and was the most efficient light source in terms of ‘crop per watt’. Finally, further applications of the work such as those for commercial horticulture and farming in closed plant production systems are presented, and it is concluded that LED lighting is likely to have a crucial role in the future of global food security.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:724846 |
| Date | January 2017 |
| Creators | Smith, Hayley L. |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/44338/ |
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