The invention provides a lighting system (100, 200, 300) for controlling the growth of plants, the system comprising; an array of solid state/semiconductor light sources (101, 201, 301) adapted to emit light of a predetermined wavelength or wavelength range; and a cooling arrangement(102, 202, 302) comprising a pipe (103, 203, 303) having at least one inlet opening for receiving a gaseous cooling medium and a plurality of outlet openings (105, 205, 305) for releasing said gaseous cooling medium from said cooling arrangement, the cooling arrangement being in mechanical and thermal contact with said light sources. The invention also provides a method for controlling the growth of a plant in a greenhouse of growth chamber. The invention allows promoting the photosynthesis of a plant by modifying the conditions (light intensity, temperature, CO2 concentration) locally around the plant.