Question

Passage cells are characteristic of
A. Primary endodermis of dicots
B. Secondary endodermis of monocots
C. Bundle sheath of leaves
D. All of the above

Answer 1

Hint: The passage cells are situated near the vicinity of the xylem elements in the endodermal area of the roots. They play the same role as the word 'passage' in their name indicates. They are not suberized, remain thin and are found in old plant roots and make symplastic flow, typically found in the root of the plant.

Complete answer: There are some endodermal cells in the roots that are modified to allow water to be transported. They are the opposite cells to the components of the protoxylem. These cells have a thin wall and suberin-like Casparian strips have no deposition. Due to their role of transporting water and mineral salts from the cortex to the xylem components, these cells are known as passage cells. In the endodermis of the older roots of monocots, passage cells are the unthickened cells that are normally located in the monocot root to begin the symplastic movement or flow to the inside. In order to allow the movement of solvents such as calcium and magnesium into the stele, passage cells operate. But most of the endodermal cells, with the exception of the monocot root, prevent water and other solvents from dissolving in water. Water passes in or out of the apoplast component of the xylem.
Hence, the correct answer is option B.

Note: The endodermis helps to prevent embolisms in the water column from occurring. In the form of amyloplasts, endodermal cells can contain starch granules. In certain plants, this can act as food storage and are shown to be involved in gravitropism. The Casparian strip is a band of material from the cell wall accumulated in the endodermis radial and transverse walls. Chemically, it is distinct from the rest of the cell wall.