The cell walls of collenchyma cells are distortable when stretched. This quality is especially advantageous in growing plant organs. It enables the collenchyma cells to stretch in synchrony with the other cells without spoiling the toughness of the tissue. The new state is stabilized by the simultaneous working-in of additional wall material. The other truly supporting tissue is the sclerenchyma.
Sclerenchyma cells are the principal supporting cells in plant parts that have ceased elongation.
It is their hard, thick walls that make sclerenchyma cells important strengthening and supporting elements in plant parts that have ceased elongation. The difference between fibres and sclereids is not always clear. Transitions do exist, sometimes even within one and the same plant. Fibres are generally long, slender, so-called prosenchymatous cells, that occur usually in strands or bundles. Such bundles or the totality of a stem's bundles, for example, are colloquially called fibres.