Abstract: The invention provides a fluorescent lamp for plant growth capable of controlling morphology in terms of grass height, area and shape of leaves and so forth, approximating those obtained under natural daylight, while effectively promoting photosynthesis of the plant. The fluorescent lamp has a glass tube and a fluorescent layer formed on the inner surface of the tube and composed of four fluorescent components having light emission peaks in the bands of 440 to 460 nm, 540 to 560 nm, 600 to 620 nm and 700 to 800 nm, respectively, said fluorescent layer having the PF ratio ranging from 0.8 to 1.2 in terms of the ratio between the photon flux PF contained in the wavelength band of 600 to 700 nm to that in the wavelength zone of 700 to 800 nm.

Abstract: Disclosed are a method and an apparatus for controlling the plant growth with artificial light in plant factories, atria, etc. The stem extension and the leaf/stem dry weight ratio can be controlled artificially by the ratio of the additional far-red irradiation (700-800 nm) to the photosynthetically active radiation (PAR 400-700 nm). In a chamber for cultivating plants, an artificial lighting source, having 3-band fluoscent lamps for PAR and far-red fluoscent lamps for far-red radiation, is employed.