Photobiology in protected horticulture

The introduction of high power LED lighting systems for horticulture has stimulated substantial interest from both the research community and the protected horticulture industry. LED lighting systems have the potential to reduce electrical energy consumption compared to conventional high pressure sodium lights and their energy efficiency continues to improve. In addition to the potential of LEDs to reduce carbon footprints and reduce running costs, LED lighting also provides considerable opportunities to exploit the wealth of photobiological knowledge to produce horticultural benefits. The narrow emission spectra of LEDs allows lighting systems to be tightly designed to stimulate specific plant photoreceptors, allowing plants to be manipulated to produce desirable characteristics. Lighting systems can be designed to maximize growth, control morphology, and optimize flavor and pigmentation. This review outlines how the light spectrum influences photosynthesis and how plant photoreceptors sense light and control growth. The review then discusses the ways in which this knowledge is being implemented in commercial horticulture to improve factors such as yield, flavor, color, plant growth, and flowering as well as pest and pathogen management and control. Research in this area is moving rapidly as the LED systems improve and increase in efficiency and as the range of novel horticultural applications expands.