Bamboo is not a wood but a plant. The veneer originates in the stems of the plants. 

Bamboo is one of the fast-growing plants in the world. After 5 years, a stem can be harvested. After harvesting, the bamboo stems are split and the outer skin is removed. The strips are naturally a light yellow color (natural), but can be steamed to a light brown color (caramel). After treatment and drying, the strips are ready to be processed into the finished product in various ways. 

What does "plain pr" mean? 

The strips are placed horizontally side by side and glued together. This creates a wide line pattern in which the characteristic bamboo pods are clearly visible.