The deposition of carbohydrates and lignin in the cell walls of Calamus simplicifolius during development

The deposition of lignin and carbohydrates in different cells and morphologically distinct cell wall layers during the development of Calamus simplicifolius was investigated by combined microscopic techniques. Lignin autofluorescence images showed that protoxylem vessels were the first to differentiate among vascular elements. At the subcellular level, high spatial resolution Raman images revealed that the deposition of carbohydrates in fibers preceded that of lignin. Additionally, the lignin and carbohydrates concentration in the secondary wall (SW) varied among different cell types. The carbohydrates concentration in SW of fibers presented the highest level, which was much higher than that in vessels and parenchyma. High concentrations of lignin were most visible in the SW of vessels, followed by fibers, with the lowest amount visible in parenchyma. Within the morphologically distinct cell wall layers, the carbohydrates and lignin in fibers SW and cell corners deposited rapidly at the early stage from the 7th to the 10th internode, while the deposition rate decreased from the 10th to the 50th internode. The findings have substantial theoretical significance to understand the biosynthesis of rattan cell walls.