Q.Passage cells are found in -

Passage cells are a special category of endodermal cells that stay thin-walled and Casparian-strip-free, permitting continued water movement into the stele.

The endodermis is the innermost layer of the root cortex, encircling the stele. Young endodermal cells develop a band-like thickening of suberin on their radial and tangential (anticlinal) walls, called the Casparian strip, which forces water to cross the endodermis symplastically (through the cytoplasm) rather than through the walls.

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Epidermis belongs to the epidermal (dermal) tissue system, not to the ground tissue system; cortex, endodermis and pericycle are all parts of the ground tissue system.

The three tissue systems of a plant, based on position, are:

1. Epidermal (dermal) tissue system — the outermost covering of the plant body, made up of epidermal cells, stomata and epidermal appendages (trichomes, root hairs).
2. Ground tissue system — all tissue lying between the epidermis on the outside and the vascular bundles on the inside. It comprises the cortex, endodermis, pericycle, pith and medullary rays, made up mainly of simple tissues (parenchyma, collenchyma, sclerenchyma).
3. Vascular tissue system — the conducting tissue, xylem and phloem, arranged into vascular bundles. …

Endodermis is the innermost layer of the cortex; in roots it is invariably a single (one-cell-thick) layer, though in aerial stems of a few plants it can be multiseriate.

The endodermis forms the boundary between the cortex and the stele (vascular cylinder). Its cells are usually barrel-shaped, arranged compactly without intercellular spaces, and bear a band of suberised/waxy material on their radial and tangential walls called the Casparian strip, which forces water and solutes to cross a living membrane (apoplast-to-symplast switch) before entering the xylem.

Checking each option:

• (a) is wrong, a collenchymatous layer just below the epidermis describes the hypodermis of a dicot stem, not the endodermis.
• (b) is wrong, several layers of parenchymatous cells just internal to the endodermis describes the pericycle, not the endodermis. …

Casparian strips are a waxy (suberin) band found in the radial and transverse walls of endodermal cells in roots.

In the primary structure of a dicot root, the endodermis is a single layer of barrel-shaped cells forming the innermost boundary of the cortex, immediately surrounding the vascular (stele) tissue. Its radial and transverse walls (but not the tangential walls) contain a band of suberin, a waxy, impermeable substance, called the Casparian strip. Because this strip blocks the free (apoplastic) movement of water through the cell w …

Casparian strips are waxy (suberin) bands present in the radial and transverse walls of endodermal cells surrounding the vascular tissue of a root; they are a feature of root anatomy, so the correct answer is Dicot root.

In the primary structure of a root, the innermost layer of the cortex is a single layer of compactly arranged cells called the endodermis, which encircles the vascular bundle (stele). Each endodermal cell wall (on its radial and transverse faces, not the tangential faces) develops a band-like thickening made of suberin, a waterproof fatty substance. This thickened band is called the Casparian strip.

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Pith is the innermost ground tissue of the stem, composed of parenchyma cells, mainly meant for food storage.

In a typical dicot stem cross-section, the tissues from outside to inside are: epidermis, cortex (with hypodermis, general cortex, and endodermis), the ring of vascular bundles, and finally the pith at the very centre. The pith is composed of large, thin-walled, loosely arranged parenchyma cells with intercellular spaces. Its main functions are storage of food materials (starch, and sometimes other reserves) and, because the cells are turgid, it also provides some mechanical support to the young stem. In some plants the pith may break down as the stem matures, leaving a hollow …