Some aspects of the light environment

Abstract

Roles of light as energy and signal sources for growing plants are discussed mainly with respect to photosynthesis and photomorphogenesis. Components of the light environment above and within a plant canopy, such as spectral distribution, photosynthetic photon flux density (PPFD), lighting cycle, and lighting direction, are shown. Characteristics of LED arrays as light source and characteristics of light environment in plant factory with artificial lighting (PFAL) are discussed. Concepts and significances of supplemental upward lighting in the PFAL and supplemental lighting in greenhouse are described. Advantages of supplemental upward lighting in the PFAL to prevent senescence of lower leaves and increase marketable fresh weight of leaf lettuce plants are shown. Strategy of environmental control under artificial lighting is discussed.