Abstract: A method of improving the growth and/or pathogen resistance of a plant, comprising the step of exposing at least part of the plant to a transient period of high intensity illumination providing a photon flux at the plant surface having at least one of the following characteristics: (a) a red photon flux comprising at least 100 micromoles photons per square meter per second, and having a wavelength of between 600 and 700 nm; (b) a blue photon flux comprising at least 100 micromoles photons per square meter per second, having a wavelength of between 420 and 480 nm. The Invention also provides apparatus for providing such conditions to growing plants.

Abstract: A method of improving the growth and/or pathogen resistance of a plant, comprising the step of exposing at least part of the plant to a transient period of high intensity illumination providing a photon flux at the plant surface having at least one of the following characteristics: (a) a red photon flux comprising at least 100 micromoles photons per square metre per second, and having a wavelength of between 600 and 700 nm; (b) a blue photon flux comprising at least 100 micromoles photons per square metre per second, having a wavelength of between 420 and 480 nm. The Invention also provides apparatus for providing such conditions to growing plants.

Abstract: A method of altering the level of at least one phytochemical in a plant cell comprising chlorophyll or in plant tissue comprising chlorophyll by irradiating the said plant cell or plant tissue with light of at least one wavelength selected from the range of wavelengths of from 400 nm to 700 nm, use of wavelengths of light selected from said range for altering the level of phytochemicals in plant tissue, harvested plant parts comprising altered levels of phytochemicals, and apparatuses for generating plant tissue having altered levels of phytochemicals therein.