Question

In Selaginella stem, trabeculae represent modified
A) Phloem cells
B) Endodermal cells
C) Pericycle Cells
D) Cortical cells

Answer 1

Hint: Phloem cells are part of vascular tissue in plants which helps in the transportation and distribution of organic nutrients. Endodermal cells help water and nutrients to get into the plant. The pericycle is a cylindrical structure of sclerenchyma or parenchymal cells. Cortical cells are present in the cortex of the plant.

Complete answer:
Option A: Phloem cells are present inside the stele and they work as vascular tissue while the trabeculae are present outside the stele and present as modified form of endodermal cells. Hence Option A is incorrect.
Option B: Trabeculae in Selaginella stem are a modified form of endodermal cells. Before generation of a gap between stele and cortex, these are known as endodermal cells Hence Option B is correct.
Option C: The trabeculae is present between the stele and cortex while the pericycle is the outermost layer of the stele so it is in contact with trabeculae but it can not be the trabeculae. Hence Option C is incorrect.
Option D: Cortical cells are present in the cortex region of the stem and it is separated by trabeculae from the stele, so cortical cells can not be the trabeculae. Hence Option D is incorrect.

Thus, the correct answer is option (B) Endodermal cells.

Note: Endodermal cells in selaginella made of Casparian strips and as the stem grows these unique cells modify themselves into trabeculae and hold the large air spaces between the stele and cortex.