Variations in the Vascular Bundle and Fiber Structure during the Stem Development of Rattan (Calamus caesius Blume)

Abstract

Calamus caesius is one of the most well-known commercial climbing palm species across the world. A comprehensive understanding of the growth-dependent variation in microstructure and polymer distribution can provide fundamental information to guide its end-use applications. In this study, we investigated the age-wise characteristics of rattan stems and the ultrastructure of fibers using electron microscopy, light microscopy, and FTIR. The results showed that the frequency of vascular bundles with a diameter of 0.55∼0.62 mm in C. caesius was 3.49∼3.97 pieces/mm2. The diameter and length of the metaxylem vessel were 0.32∼0.34 mm and 2.86∼3.00 mm, respectively. Cellulose, lignin, xylan, and HCA are mainly concentrated in the fiber sheath of vascular bundles. The distribution of major polymers in positions other than the top was relatively stable. The tissue proportion of parenchyma, xylem, and phloem did not differ significantly at different positions. The proportion of fibers from 22.27%∼25.33% showed significant differences. The fiber length was 1.43∼1.76 mm, and the diameter was 10.78∼12.63 μm. During the growth process of the rattan stem, the secondary wall of fiber cells continued to accumulate inward towards the cell cavity from 2 to 6 layers. The unique fiber properties and stable vascular bundle composition of C. caesius may have potential in fields such as composite materials or renewable energy.