Light environment and plant growth in plant factories

Abstract

A plant factory with artificial light is an effective system producing food to satisfy specific demands on yield, morphology, taste and nutrient accumulation in plants. All environmental factors inside a plant factory can be controlled without climate and location limitation. Light is one of the most important factors affecting plant growth and quality. By regulating light aspects, such as light intensity, light period, light quality, lighting position, and daily light integral, the growth and quality of the plants grown in a plant factory can be largely enhanced. As known, the initial and operating cost for a plant factory with artificial light is high, particularly the cost of electrical energy related to lighting. Identifying the optimal light environment that promotes plant growth and quality is critical for commercialization of plant factories. Recent researches have paid great attentions to the effects of light environment on the growth and morphology of leafy vegetables. On the other hand, the demand on functional plants that contain high concentration of bioactive compounds is increasing rapidly. Bioactive compounds in plants have been intensively studied to evaluate their effects on human health and many of them are proved to be clinically active against various types of diseases (e.g. anti-cancer effects). More and more people prefer to take health product derived from natural plants for disease prevention. Solutions to realize sustainable production of high quality functional/medicinal plants can be provided by developing environmental control technologies, such as light recipe, in plant factories. Aromatic herbs such as coriander; medicinal plants such as perilla and water spinach are subjected to different light conditions and root zone environments. Some bioactive compounds e.g. perillaldehyde and rosmarinic acid in perilla leaves; phenolic compounds and flavonoids, especially rutin and chlorogenic acid in coriander can be enhanced. The effects of each light aspect on plant growth vary with plant species and other environmental conditions, however, there are also some general trends that can be used to guide commercial application. This presentation introduces the basic of light and its effects on plant growth in plant factories, demonstrates research results that have been published in scientific journals, reports the current study on herbs and medicinal plants, and summarizes the general application of light in plant production.