Fuente: WIPO "tomato" An apparatus configured for integration into a greenhouse is provided. The apparatus includes a motor and a sheet of woven polymeric material that includes fluorophores. The sheet can be automatically deployed or retracted on demand, via operation of the motor, in order to deliver a dynamic spectrum of light to plants within said greenhouse. In another aspect, an optical element including a sheet with at least two distinct film segments is provided. Each distinct film segment has a different fluorescent spectra than other distinct film segments, said differing fluorescent spectra providing differing wavelength ranges along the length of each distinct segment, such that as the sheet is moved through a greenhouse the spectrum of light changes. An agricultural greenhouse including such an apparatus and/or optical element is provided in another aspect.