The use of light-emitting diode systems for improving plant propagation and production^©

INTRODUCTION
The propagation stage of plant production can be challenging but the quality of the resulting seedling, rooted cutting or young plant is crucial to the performance of the finished crop. In protected horticulture many aspects of the crop environment such as temperature, humidity and irrigation, are carefully controlled to optimise plant performance. However, despite the importance of light to the process, many propagation systems rely on solar radiation which varies through the season and from day to day, resulting in crop variability.
High pressure sodium and other types of high intensity discharge lamps have been used to provide supplemental lighting. While these can improve plant growth they can also result in stretching due to the lack of blue light in their output spectrum. The introduction of light-emitting diode (LED) lighting systems for horticulture caused great interest due to the potential energy savings compared with traditional lighting systems (LEDs use 25% less electricity than 600W HPS lamps for an equivalent light intensity). However, there is a growing body of evidence that suggests LEDs provide many additional benefits beyond simple energy saving that may have a greater impact on crop production, for example by being able to “tailor” the output light wavelength to meet specific crop management requirements.