The phloem sclerenchyma is one of the major components of the phloem in vascular plants. The others are sieve elements, companion cells, and phloem parenchyma. The phloem is the vascular tissue responsible for the translocation of photosynthate materials throughout the plant. The phloem sclerenchyma includes the phloem fibers and the sclereids. They are specialized sclerenchyma cells. They provide the plant mechanical support as both of them have thick, lignified cell walls. Apart from the primary cell wall, they form secondary cell wall in between the primary cell wall and the plasma membrane. The phloem fibers are able to provide tension strength without limiting flexibility (unlike sclereids).
The phloem fibers are narrow and elongated, and in some plants, are relatively longer. They are found both in the primary phloem and the secondary phloem. In the secondary phloem, though, the phloem fibers form the bast fibers. The bast fibers are the durable, nonliving sclerenchyma fiber in the secondary phloem. Some of the bast fibers are commercially important. Because of their commercial value, they are collected and marketed as:
- bast fibre (British)