EFFECTS OF ALTERNATING LIGHT INTENSITY ON CO2 ASSIMILATION OF FICUS ELASTIC AND DIEFFENBACHIA PICTA PLANTS, GROWN FOR INDOOR LANDSCAPING
Indoor landscaping increasingly uses plants on new hydroponic systems, including green walls, for greening private and public spaces, not always well or sufficiently lighted. Lamps are often essential to ensure a suitable light intensity for plant growth and for the production of a dense and brightly coloured canopy, even if many commonly used species originate in the lower layers of tropical ad subtropical forests and have a high ability to tolerate poor light levels. The photosynthetic response to light flecks is a well known characteristic of many plants native of the lower layers of forest and especially those living on the floor of dark and moist tropical forests. The effects on CO2 assimilation of a constant or alternating light intensity were tested in Dieffenbachia picta Camille and Ficus elastic Decora plants, grown under 8/16 hours of day/night in a phytotron. The compared intensities were 20, 40 or 80 µmol m-2 s-1 for constant light and 20/40 or 40/80 µmol m-2 s-1 for alternating light, at 8 minute intervals. The CO2 assimilation was measured throughout the 8 hours of lighting, by an infrared gas analyzer LI-6400XT, on completely expanded leaves. The light intensity regimes influenced the trend of CO2 assimilation curves and the total daily assimilated CO2 in both species. In Ficus the photosynthetic activity under constant 20 and 40 µmol m-2 s-1 was very low (0.7-0.9 µmol CO2 m-2 s-1 on average during the 8 hour light period) and increased to 1.4 µmol CO2 m-2 s-1 under 80 µmol m-2 s-1, with two well marked peaks after 0.5 and 5 hours from the start of lighting. The 40/80 alternated intensity resulted in a total daily assimilation of 54 mmol CO2 m-2, 33.2% higher than under 80 constant lighting. In Dieffenbachia the CO2 assimilation was around 0.2-0.6 µmol CO2 m-2 s-1, averaged for the 3 constant intensities, whereas at 20/40 alternating lighting the rate increased to 1.2 µmol CO2 m-2 s-1, equivalent to +67% on total daily assimilation.
Giorgioni , M.E. 2012. EFFECTS OF ALTERNATING LIGHT INTENSITY ON CO2 ASSIMILATION OF FICUS ELASTIC AND DIEFFENBACHIA PICTA PLANTS, GROWN FOR INDOOR LANDSCAPING. Acta Hort. (ISHS) 956:239-245
artificial lighting, interior foliage plants, light compensation point, light efficiency