Question

Draw and label the diagram of T.S.of stem.

Answer 1

Hint:Stem is glabrous, cylindrical, hairy, slightly branched; grooved and ribbed; basal part of branches greenish-brown, apical part dark green, fracture low.

Complete answer:
The cross-section of the mature stem reveals many bulges in places and consists of a single layer of epidermis, surrounded externally by a striated cuticle. A number of epidermal cells are elongated to form multicellular coverings and T-shaped trichomes with 2-6 stems. Cortex 3-5 layers of thin-walled, tangentially elongated parenchymal cells. A few layers of collenchyma between the epidermis and the parenchymal cortex in the ribbed area or below the ridges.

Endodermis is a continuous single layer, consisting of barrel-shaped cells within the cortex. Two layered pericycles accompany the endotherms. The stele is made up of a ring of vascular bundles. Each vascular bundle is a joint and collateral bundle and shows a primary xylene arrangement. Phloem consists of the strands of the sieve tubes, the companion cells and the parenchyma phloem. Xylem is an endarch and consists of a vessel, a parenchyma and a fibre.Between the xylem and the phloem, cambium is found.

The central portion of the pit is composed of hexagonal to polygonal, thin-walled parenchyma cells. Root shown outer 3-4 layered cork with dark reddish brown is present in between the vascular bundles, medullary rays or pith rays. The secondary cortex is large and composed of thin-walled, parenchymal cells with a few resin ducts. The inner portion of the cortex is endodermis. It encloses the internal vascular tissues.

Phloem is present on the outer side and is multi-layered, consisting of sieve elements and phloem parenchyma. Xylem is large and endarchy made up of vessels, tracheids, fibres and xylem parenchyma, which are crossed by xylem rays. There's a tiny spot in the middle.

Note:Its main role is to sustain the plant by carrying leaves , flowers, and buds; in some cases, stems also store food for the plant. A stem, like that of a palm tree, may be unbranched or may be heavily branched, like that of a magnolia tree.