4.4—Cellulose microfibrils and secondary thickening

Plant fibres gain tensile strength from cellulose microfibrils arranged in a strong mesh and from secondary thickening of the cell wall, often with lignin.

Parallel or layered microfibrils distribute pulling forces, while a thick secondary wall resists stretching. These properties make sclerenchyma fibres and xylem useful as structural materials.

A rope made from plant fibres depends on the same principle: long, hollow fibres with thickened walls tolerate tension. The material can be exploited without confusing strength with flexibility or transport.

Sclerenchyma fibres support but do not conduct water; xylem also supports while conducting. A thick wall can strengthen a cell but can also prevent living contents and membrane transport.