Effects of LED Light Quality Combinations on Growth and Leaf Colour of Tissue Culture-Generated Plantlets in Sedum rubrotinctum

Different plants have different requirements with regard to light quality, including combinations of R/B LED light on tissue-culture-generated plants. However, the effects of R/B LED light combinations on the growth and colour changes of leaves in succulent plants remains unknown. In this study, to identify the most beneficial light quality and R/B light ratios for the growth of the succulent plant species Sedum rubrotinctum and its production of attractive colours, the growth parameters, pigment levels and leaf colour phenotypes of tissue-culture-generated S. rubrotinctum plantlets were evaluated when the plantlets were exposed to R, 4R1B, 3R1B, 2R4B, B and W treatments for 90 days. The results showed that light quality obviously influenced the growth and leaf colour of tissue-culture-generated S. rubrotinctum plantlets. R light hastened the elongation of stems, and B light was more beneficial for biomass accumulation and leaf and root growth. However, compared with B light, R light, and W light, the R/B combination resulted in a greater amount of fresh biomass and higher values for the shoot/root FW, stem diameter, crown width, total root length, root surface area, and root volume. The R/B combination also markedly increased the contents of anthocyanins and the R/green chromaticity of the leaves. In addition, a principal component analysis (PCA) revealed the following comprehensive ranking: 4R1B > 2R4B > 3R1B > W > B > R. Therefore, the 4R1B combination is suggested as the best treatment for promoting the growth of tissue-culture-generated S. rubrotinctum plantlets and their production of attractive colours. This study provides a practically significant and optimal solution for growth regulation via light quality for the production of S. rubrotinctum as well as important implications for other succulent plant species in the Crassulaceae family.