Question

Passage cells are thin-walled cells found in
A. Phloem elements to serve as entry points.
B. Testa of seeds for the emergence of embryonal axis
C. The central area of style for passage of pollen
D. Endodermis of root to facilitate rapid transport of water from cortex to pericycle.

Answer 1

Hint: Passage cells are also known as transfusion cells. Related to the absorption pathway of water in plants.

Complete answer:
Passage cells are present in the endodermis of the dicot root. Radial and tangential walls of endodermis cell layers have Casparian strips. The Casparian strips contain deposition of suberin, which makes them impermeable to water. These Casparian strips are absent in cells present just in front of the protoxylem and these cells are called passage cells. They are also known as transfusion cells because they help in the movement of water from the cortex to the pericycle.

Additional Information: The anatomy of dicot and monocot root is as follows:
-Epiblema or Rhizodermis layer: It consists of living tubular components and is the outermost part. No cuticle and stomata are present. Root hairs arise from the maturation zone of epiblema. It helps in water absorption from the soil.
-Cortex: The cortex is made up of circular and polygonal parenchymatous cells, intercellular spaces are present.
-Endodermis: This layer is the innermost part and has Casparian strips. It is single-layered.
-Pericycle: It is composed of parenchymatous cells and consists of only one layer. The endogenous origin of roots occurs from the pericycle layer.
-Vascular Bundles: Contains xylem and phloem in radial and exarch fashion in dicots and monocots. In monocots, xylem is polyarch(more than six in number) but the number of xylem bundles ranges from two to six in dicots. A parenchymatous layer is present between xylem and phloem, which is known as conjunctive tissue. The conjunctive tissue produces vascular cambium during secondary growth in dicots but not in monocots.
-Pith: it is present at the center and it is reduced or underdeveloped in dicot root but well developed in monocot root.
So, the correct answer is, "Passage cells are thin-walled cells found in the endodermis of the root to facilitate rapid transport of water from cortex to pericycle."

Note: It should be remembered that Casparian strips are present in the epidermis of both dicot and monocot root. Monocot root anatomy is almost similar to the anatomy of dicot roots. Secondary growth is absent in the monocot roots as no cambium formation occurs.