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Pith is composed of soft, spongy parenchyma cells, which in some cases can store starch. In eudicotyledons, pith is located in the center of the stem. In monocotyledons, it extends only into roots. [1] The pith is encircled by a ring of xylem; the xylem, in turn, is encircled by a ring of phloem.
Parenchyma forms the "filler" tissue in the soft parts of plants, and is usually present in cortex, pericycle, pith, and medullary rays in primary stem and root. Collenchyma cells have thin primary walls with some areas of secondary thickening. Collenchyma provides extra mechanical and structural support, particularly in regions of new growth.
Cross-section of a flax plant stem: 1. Pith 2. Protoxylem 3. Xylem I 4. Phloem I 5. Sclerenchyma 6. Cortex 7. Epidermis. In botany, a cortex is an outer layer of a stem or root in a vascular plant, lying below the epidermis but outside of the vascular bundles. [1]
Ep = epidermis; C = cortex; BF = bast fibres; P = phloem; X = xylem; Pi = pith Women in southern Norway weaving with linden bast fibres Ndimbu mask from Tanganyika, made with wood, hair and bast Bast fibre (also called phloem fibre or skin fibre ) is plant fibre collected from the phloem (the "inner bark", sometimes called "skin") or bast ...
In a vascular plant, the stele is the central part of the root or stem [1] containing the tissues derived from the procambium. These include vascular tissue , in some cases ground tissue ( pith ) and a pericycle , which, if present, defines the outermost boundary of the stele.
Helianthus stem in section. The cells of the vascular cambium (F) divide to form phloem on the outside, located beneath the bundle cap (E), and xylem (D) on the inside. Most of the vascular cambium is here in vascular bundles (ovals of phloem and xylem together) but it is starting to join these up as at point F between the bundles.
The stem can also be called the culm, halm, haulm, stalk, or thyrsus. The stem is normally divided into nodes and internodes: [2] The nodes are the points of attachment for leaves and can hold one or more leaves. There are sometimes axillary buds between the stem and leaf which can grow into branches (with leaves, conifer cones, or flowers). [2]
The cells in vascular tissue are typically long and slender. Since the xylem and phloem function in the conduction of water, minerals, and nutrients throughout the plant, it is not surprising that their form should be similar to pipes. The individual cells of phloem are connected end-to-end, just as the sections of a pipe might be.