Effects of different irradiation levels of light quality on Chrysanthemum

The effect of light quality at two light intensities on leaf anatomy, photosynthetic efficiency and pigmentation were investigated in Chrysanthemum. Four light qualities were applied at two light intensities of 40 μmol m−2 s−1 and 100 μmol m−2 s−1 and with a photoperiod of 14 h using light-emitting diodes, which were 100% red (R), 100% blue (B), 75% red with 25% blue (RB) and white (W), respectively. Leaf anatomy responses to a lower light intensity were observed, we saw a decrease in leaf thickness for blue, red + blue and multispectral white light but not for the red wavelength. At higher light intensity we also observed a favorable effect of blue light on the anatomical development of the leaves. Both light intensity and quality affected the stomatal development. Low light decreased the stomatal index and stomatal density but increased in the stomatal area for red + blue and multispectral white light. Light intensity affected the pigment accumulation but no quality effects were present. For the lowest light level an enhanced pigment concentration was observed in Chrysanthemum this as well for Chl a, Chl b and total carotenoids. Light quality influenced the photosynthetic efficiency as observed by chlorophyll fluorescence. Monochromatic red resulted in an inhibition of Photosystem II, this at both light intensities, resulting in a decline in maximum quantum yield (Fv/Fm) and quantum efficiency (ΦPSII). Light intensity significantly influenced biomass accumulation, higher light intensity increased plant dry weight. At a light intensity of 100 μmol m−2 s−1, blue light positively influenced the biomass compared to monochromatic red.