Tag: ground tissues

In the stem, the pith and the cortex make up the ground tissue. The pith is located within the cylinder of vascular tissue, where it often exhibits a spongy texture because of the presence of large intercellular air spaces. If the growth of the pith fails to keep up with that of the surrounding tissues, the pith may degenerate, producing a hollow stem. In general, roots lack piths, although there are exceptions to this rule. 

Casparian strip is a band of cell wall material deposited on the radial and transverse walls of the endodermis. It is chemically different from the rest of the cell wall. Casparian strip is made of suberin and sometimes lignin. It blocks the passive flow of materials, such as water and solutes into the stele of a plant. 

In plant anatomy, the Casparian strip is a band of cell wall material deposited on the radial and transverse walls of the endodermis and is chemically different from the rest of the cell wall the cell wall.

Casparian strip is a band of cell wall material deposited on the radial and tangential walls of the endodermis and is chemically different from the rest of the cell wall, the cell wall being made of lignin and without suberin, whereas the Casparian strip is made of suberin and sometimes lignin. It blocks the passive flow of materials such as water and solutes into the stele of a plant. It varies in width and is often much narrower than the wall in which it occurs. It is typically located closer to the inner tangential wall than the outer. 

Passage cells are endodermal cells of older roots, which have retained thin walls and Casparian strips rather than becoming suberized and waterproof like the other cells around them, to continue to allow some symplastic flow to the inside. Passage cells function to allow transfer of solutes, such as calcium and magnesium into the stele, in order to eventually reach the transpiration system. 

In the histogen theory Henstein divided the shoot apex into various zones. Each zone consists of a group of initial cells and called as histogen or a tissue builder.

Epidermis is the part of epidermal tissue system and forms the outer protective covering of primary plant body. 

The endodermis is the central, innermost layer of cortex in some land plants. It is made of compact living cells surrounded by an outer ring of endodermal cells that are impregnated with hydrophobic substances (Casparian Strip) to restrict apoplastic flow of water to the inside. The endodermis is the boundary between the cortex and the stele. In many seedless vascular plants, the endodermis is a distinctly visible layer of cells immediately outside the vascular cylinder (stele) in roots and shoots. In most seed plants, especially woody types, an endodermis is absent from the stems but is present in roots. 

Histogen theory by Hanstein states that shoot apical meristem consists of three distinct zones- 

Protostele is the most primitive type of stele with central xylem surrounded by phloem and pericycle. Pith is absent in them. Medullation (appearance of pith) of a protostele with central pith is called as siphonostele and thus has central pith surrounded by xylem, phloem and pericycle. Separation of vascular strands by parenchyma in siphonostele give rise to eustele. Thus, the correct answer is option B.