LIGHT RESPONSE CURVES OF SELECTED PLANTS UNDER DIFFERENT LIGHT CONDITIONS

Photosynthesis rates under HPS light were measured on various plant species. Euphorbia pulcherrima, Plectranthus scutellarioides and Lactuca sativa were selected for more detailed experiments under natural light and artificial light provided by HPS lamps or LEDs under controlled environment conditions. Comparisons have been made between gas exchange characteristics including the light compensation point and the slope of light response curves under practical-relevant light intensities. Light compensation points under light qualities with input of red LEDs were between 13-15 µmol m^-2 s^-1 in all three model plants. Average photosynthetic rates at 100 and 200 µmol m^-2 s^-1 PPF red and blue/red LED light were above other calculated values for the other light qualities. The photosynthetic rates under blue/green/red LED light declined considerably less, than the purely energetic consideration would anticipate. Accordingly the green component in the spectrum contributed noteworthy to the photosynthetic performance of plants.