GROWTH AND PHOTOSYNTHESIS OF ORNAMENTAL PLANTS CULTIVATED UNDER DIFFERENT LIGHT SOURCES
New light sources for horticultural applications, intended to replace HPS lamps or fluorescent tubes, are currently being introduced in the market. Special attention is being devoted to LED technology, which permits optimisation of the spectral distribution of a light source. Consequently, LED lamps are generally assumed to be more efficient for driving photosynthesis that HPS lamps, for which much of the wavelength is outside the photosynthetic optimum range. In order to investigate the efficiency of LED technology in greenhouse applications, different types of LED lamps were compared with conventional HPS lamps in a series of experiments with Euphorbia pulcherrima. Cultivation took place in greenhouse conditions with natural daylight and 100 µmol m-2 s-1 supplementary lighting, supplied by white LED, red/blue LED or conventional HPS lamps (control). Plant development and photosynthesis rate were monitored over 4 months. Shoot elongation was highest for plants grown under HPS lamps, as was fresh weight. Measurements of photosynthesis under the different light sources revealed a trend for higher photosynthesis when white LEDs were used. However, when photosynthesis was measured at different light intensities using red/blue LEDs, plants grown under HPS lamps had the highest photosynthesis. The air temperature in the canopy was lower when the light was supplied with LEDs than with HPS lamps, thus delaying development. We concluded that the quality of light supplied was a significant factor for plant development in greenhouse conditions with supplementary light. There was a lack of correlation between measured photosynthesis and biomass production.
Bergstrand , K.-J. and Schüssler, H.K. (2012). GROWTH AND PHOTOSYNTHESIS OF ORNAMENTAL PLANTS CULTIVATED UNDER DIFFERENT LIGHT SOURCES. Acta Hortic. 956, 141-147
Euphorbia pulcherrima, high pressure sodium lamps, light emitting diode, photosynthesis measurements, supplementary lighting