| MadSci Network: Botany |
Not all plant parts are stiff; some are flexible such as nonwoody stems and celery stalks and other leaf petioles. Flexible support is often provided by collenchyma cells. Stiff or rigid plant parts, such as spines and thorns are often composed mainly of sclerenchyma cells. Sclerenchyma cells are dead at maturity and have thick secondary cell walls. Their cell walls are often impregnated with lignin which makes them stiff. Sclerenchyma cells are of two general types, fibers and sclerids. Fibers are elongated while sclereids are not. The first reference has three webpages on sclerenchyma cells. Woody stems contain fibers but mainly consist of xylem vessels or tracheids. They are both elongated cells that are similar to sclerenchyma because they are dead at maturity and have thick, secondary walls and lignin. References Sclerenchyma cella Secondary cell walls Wood micrographs
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