culms

Culms are the most distinguishable part in a bamboo plant species, for its varied sizes, diameters, colors and textures. They are usually hollow, but there is exceptions. Internodes of Chusquea genus, of Central and South America, are solid, as the Dendrocalamus Strictus species. Some species have water inside the internodes. One species has naturally square culms, with round edges, the Chimonobambusa quadrangularis. It's possible to induce a form to the culm, by containing culm growth to a height of a meter and a half. The soft shoot adapts to box format and so its telescopic culm. Then the culm rises with the new format, square, triangular, etc...

Bamboo culms are made with fibers that reach the lenght of centimeters, composed with lignin and silicate. According Mr. Stanford Lynx "the bamboo cell wall is a composite made of a rigid cellulose polymer in a matrix of lignin and the hemicelluloses". Silicate aggregate mechanical resistance to bamboo. The lignin matrix gives its flexibility.

The shoot growing from a rhizome is a still "closed" culm, and totally protected by culm sheaths. It reminds a closed telescope, and, as it grows, its separated internodes gets out of one another, as in an open telescope. In its initial growth fases we can see the fastest growth rates of vegetal reign , in some giant species growing 40 cm in 24 hours. At the end of the first year the bamboo had completed its growth. The culm sheaths protect the internodes until the essential growth has completed, then they dry and fall.

The culm sheaths comprise the sheath itself and the blade, also the ligule with fringes, and two auricles with its bristles. These little parts helps identifying a bamboo species. The culm sheaths of superior nodes possess longer blades than inferior ones.