Growth and photosynthesis of Lemna minor L. exposed to different light conditions and sucrose supplies

Abstract

Duckweed (Lemna minor L.) is a model plant suitable for investigation intoplant physiology, biochemistry and ecotoxicology. Depending on the type of the experiment,duckweed is cultivated on different nutrient media under various chamber conditions.In our work, duckweed was cultivated on Pirson-Seidel’s nutrient solution supplementedwith 5, 7.5 or 10 g L–1 sucrose under cool white (CW) or Gro-Lux (GL) lightsources. When different light sources and sucrose supplies are compared, a significantstimulative effect of GL light on duckweed grown on 7.5 and 10 g L–1 sucrose was seen tostart on day 9. Considering photosynthetic performance the results showed that there wereno significant differences in maximum quantum yield of PSII (Fv/Fm) after 7 and 16 days ofexposure, regardless of light source and sucrose supply. Effective quantum yield of PSII(FPSII) decreased only after 16 days of exposure to 5 g L–1 sucrose under CW light. Thehigher growth rate and photosynthetic performance in plants exposed to GL light is a consequenceof its spectral distribution resembling the action spectrum of photosynthesis. Furthermore,enhanced growth noticed in plants cultivated on higher sucrose contents (7.5 and10 g L–1) indicated the promotive effect of sucrose in plants grown under low light conditions.