Sclerenchyma


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Sclerenchyma

Single cells or aggregates of cells whose principal function is thought to be mechanical support of plants or plant parts. Sclerenchyma cells have thick secondary walls and may or may not remain alive when mature. They vary greatly in form and are of widespread occurrence in vascular plants. Two general types, sclereids and fibers, are widely recognized, but since these intergrade, the distinction is sometimes arbitrary.

Sclerenchyma

 

in plants, mechanical tissue consisting of two types of thick-walled and usually woody cells: fibers and sclereids.

The fibers are greatly elongated cells, usually ranging in length from fractions of an mm to 1 cm (nettles). Some plants, for example, the ramie, have fibers reaching 4 cm in length. The fibers have sharp ends and porous layered walls. Nonwoody fibers of sclerenchyma having cellulose walls, for example, in flax, are a valuable raw material for the textile industry. Sclerenchyma fibers are as durable as steel and as resilient and elastic as rubber. The amount and distribution of the fibers determine a plant organ’s durability when subjected to stretching, compression, and bending.

In many plants the fibers form a mechanical facing for the vascular bundles. In the stems of dicotyledons they are found mainly in the pericycle and the primary phloem. In the stems and leaves of monocotyledons the fibers often form subepidermal cords, whereas in the roots they are concentrated primarily in the center. In addition to fibers of first derivation formed from the cells of the basic meristem and procambium, the term “sclerenchyma” is also applied to phloem and xylem (libriform) fibers of cambial origin.

For information on sclereids see.

L. I. LOTOVA

sclerenchyma

[sklə′reŋ·kə·mə]
(botany)
A supporting plant tissue composed principally of sclereids whose walls are often mineralized.
References in periodicals archive ?
5 cm, with 50-80 pairs of pinnae; rachis sclerenchyma slightly exposed and rounded abaxially, darkened, ca.
The cross-sections, the needle width and thickness, and separately the areas of epidermis, mesophyll, xylem, phloem, and sclerenchyma were examined under microscope (Micros MC400A) at x 100 magnification and photographed with a Nikon Coolpix 5400 digital camera.
It is suggested that smooth surfaces correspond to small mastoids embedded in the subepidermal sclerenchyma.
Sclerenchyma bands with associated brachysclerids run longitudinally through the mesocarp and a layer of tanniferous cells internal to the endocarp (Fig.
5 cm wide), clathrate and iridescent rhizome scales that are glabrous throughout or with only one apical cilium, laminae with only one sorus per segment, and fertile veins that present the sclerenchyma visible beneath the sporangia.
For untreated and AB-treated stems, the initiation of observable ruminal degradation of cell wall was prolonged from 12 h for inner parenchyma to 24 h for sclerenchyma and to 48 h for phloem of small vascular bundles, while the outer epidermis was intact even at 72 h.
Lin and De Vol (1977) present a key to Taiwan ferns on the basis of petiole structure, and they provide diagnostic value to the number and shape of vascular bundles, sclerenchyma distribution, presence and number of adaxial grooves, ventilation areas and indument.
Perigynium, number of sclerenchyma traces (nerves): <25 (0), 25 39 (1), 40-60 (2) The plesiomorphic state is indicated by "(0)" and the apomorphic state(s) by "(1)," "(2)," and "(3)" Table 5 Taxon x Character State Matrix for Phylogenetic Analysis of Carex section Deweyanae Character no 1 2 3 4 5 6 7 atlantica ssp.
A sclerenchyma zone of 4-5 cell layers is found in the abaxial cortex, near to the epidermis.
The anatomy was simple, the central strand of sclerenchyma of the algal progenitors becoming a strand of tracheids forming the earliest type of stele, the protostele.
Xylem is not, however, of primary significance in the mechanical strength of Equisetum stems, because sclerenchyma is relatively abundant (Jeffrey, 1899; Hauke, 1978).