Internal stress development was investigated in rattan canes (Calamus merrillii Becc.) following the procedures used in trees. Measurements showed that longitudinal compressive stresses existed at the periphery while longitudinal tensile stresses existed at the core. Such stresses originated from the fibers. Fiber MFA was observed to be beyond 20" and the lignin content was above 30%. Considering its similarities to compression wood tracheids, it was assumed that the rattan fibers generated longitudinal compressive stress. The amount of stress varied from base to top and from periphery to core because of the variation in the proportion of fibers along these points. This is why the longitudinal compressive stress that was generated at the base was higher than at the top and high longitudinal compressive stress was developed at the periphery. As a response to this high peripheral stress, longitudinal tensile stress was induced at the core.
The influence of structure on the thermal softening of Palasan canes was evaluated using the creep compliance test. The canes revealed compliance curves similar to wood. Correlating the average compliance per temperature to ground parenchyma and fiber area percentage showed that the former promoted thermal softening while the latter inhibited it. This thermal response was highly affected by the ratio between the heat resistant cellulose and heat sensitive hemicellulose components of the cell wall. Ground parenchyma cells with high hemicellulose content favored thermal softening, while fibers with high cellulose content inhibited it. Therefore, the degree of thermal softening is dependent on the proportion of ground parenchyma present within the region. If the ground parenchyma percentage is high it is expected that the amount of softening will be large and vice versa.