Modern Phytomorphology 5: 73–78, 2014 © e Author(s), 2014 Introduction Plants constantly have to adaptable to changing conditions of the environment, including to conditions of the lighting (Gumiński 1990; Lamparter et al. 1998; Kern & Sack 1999; Suetsugu & Wada 2003; Huunen et al. 2005; Cerff & Posten 2012). ese organisms receive the light signals through specialized photoreceptors (Brigss & Christie 2002; Hetmann & Kowalczyk 2011; Li et al. 2012; Matioc- Precup & Cachiţă-Cosma 2012), such as phytochromes, cryptochromes and fototropines. With their help, the plants have got the informations about the quantitative and qualitative changes in the composition of the spectral lights and about the time of the light exposure. Among cryptogamous plants like as mosses, the signals of light are perceived by specialized receptors similar to the signals known in plants vascular. On the molecular level in the genomes of Funaria Hedw. and Physcomitrella Bruch & Schimp. were detected CRY genes, alike under construction to the genes described in Adiantum cappillus-veneris L. and Arabidopsis thaliana (L.) Heynh., which regulate the operation of cryptochrome (Suetsugu & Wada 2003). Besides, the construction of structure and expression of genes encoding phytochrome are beer known in the mosses (P asentsis et al. 1998; Zeidler et al. 1998). For many species of mosses living in the lowest layers of the forest, the direct sun rays get to them in a small degree. And some moss species have thin lipid layer that protects them from the damaging effects of light. Others IMPACT OF LIGHT SPECTL COMPOSITION ON THE LENGTH AND WEIGHT OF THE GAMETOPHYTE OF POLYTRICHASTRUM FORMOSUM (HEDW.) G.L. SMITH, PLAGIOMNIUM CUSPIDATUM (HEDW.) T.J. KOP. AND PLEUROZIUM SCHREBERI (BRID.) MI. Katarzyna Możdżeń 1 *, Diana Saja 1 **, Magdalena Ryś 2 , Andrzej Skoczowski 1 *** Abstract. e aim of the present study was to examine the influence of light spectral composition on the length and weight of mosses gametophytes: Polytrichastrum formosum (Hedw.) G.L. Smith, Plagiomnium cuspidatum (Hedw.) T.J. Kop. and Pleurozium schreberi (Brid.) Mi. Plants were grown 31 days in the chambers equipped with LEDs matrices of the same intensity of light (200 µmol m -2 · s -1 ), but different spectral composition: white (WL), white-blue (WBL) and red-green- blue (RGBL). It was found that the WBL as compared to RGBL inhibited the growth of the whole gametophytes of P. cuspidatum and P. formosum. WBL inhibited also rhizoids length of P. cupsidatum, in comparison to plants growing on WL and RGBL as well as growth of leaves stalks P. schreberi and P. cuspidatum as compared to WL. For RGBL fresh weight of plants P. cuspidatum was significantly higher than the WBL, while in P. schreberi higher than that for WBL and WL. Impact of light quality on the dry maer production was observed only in P. schreberi. Effect of spectral composition of light on the length and weight of the gametophyte depends on the species of moss. Key words: Polytrichastrum formosum, Plagiomnium cuspidatum, Pleurozium schreberi, spectral composition of light, mosses, gametophytes, growth 1 Department of Plant Physiology, Institute of Biology, Pedagogical University, Podchorążych str. 2, Cracow 30-084, Poland; * kasiamozdzen@interia.pl; ** dianasaja@gmail.com; *** skoczows@up.krakow.pl 2 Institute of Plant Physiology, Polish Academy of Sciences, Niezapominajek str. 21, Cracow 30-239, Poland; mtroc@i-pan.krakow.pl