In vitro rooting, plant growth, monosaccharide profile and anatomical analysis of Phalaenopsis regenerants under different regions of visible light

The emergence and application of light-emitting diodes (LEDs) as an adjustable light source, developed our knowledge about the role of various light parameters in plant growth and development. Our aim was to evaluate the rooting of regenerated shoot tips and subsequent survival rate of Phalaenopsis tissue cultured plantlets by analyzing the monosaccharide profile and anatomical evaluation of regenerated roots under eight-light wavelengths including red (R), blue (B), green (G), red+blue (RB), red+green (RG), blue+green (BG), white (W), and Fluorescent (FL). The results revealed different responses depending on the type of light quality. Rooting traits were better under FL and G light; however, the maximum root length was obtained under white LED. In general, rooting was not suitable under RG light. Despite the high fresh and dry weight of roots under RB light, leaf length decreased. Leaf length was better under FL and G followed by R and W and decreased under spectra containing blue light. Also, the content of chlorophyll under FL and G was balanced and the levels of anthocyanins and carotenoids in FL and G were lower than in blue light and treatments containing blue. The highest content of monosaccharides (glucose, xylose, galactose, rhamnose, arabinose, and mannose) was obtained under RB and FL followed by the G light. The lowest content of monosaccharides was recorded under RG and BG. Analysis of the root showed that the size of the cells in this area was larger under fluorescent and green light. Expanded leaves, balanced monosaccharide and pigment levels, and large cells of the root cortex were common features of FL and G light, which also led to the highest ex vitro survival rate.