Question

Endodermis of dicot stem is also called
A. Bundle sheath
B. Starch sheath
C. Mesophyll
D. Water channel

Answer 1

Hint: Endodermis layer present in the cortex. It is the only innermost layer which separates the cortex and vascular bundles. They are compactly arranged and have no intercellular space. Cells are barrel-shaped.

Complete answer:
The vascular system is more complex in dicot plants as compared to the monocots plants. The vascular bundles are arranged in a ring around the pith in the dicot stem. The phloem and xylem are separated by a vascular cambium. The vascular bundle is collateral, open, conjoint and endarch. The following are the parts of primary dicot stem in the plants. They are epidermis, hypodermis, cortex, endodermis, pericycle, vascular strands, medullary/pith rays and pith or medulla.
Above is the general discussion of the dicot stem, now let us discuss the given option one by one:
Option A: Bundle sheath: The movement of substance inside vascular tissue and the parenchyma is regulated by a bundle of sheaths; it also avoids the air exposure of the vascular tissue in plants. This happens because in plants the vascular bundle is covered by a region/layer of compactly arranged cells.
Option B: Starch sheath: The other name for stem endodermis is starch sheath because there is a conspicuous starch grain-like food reserve in the endodermal cells. The thickness of an endodermis is a layer of one cell which is present at the boundary of cortex and has barrel-shaped cells which do not enclose any kind of intercellular spaces as there is an absence of Casparian strips.
Option C: Mesophyll: Mesophyll also known as chlorenchyma cells is a kind of tissue which exists in the inside of leaves which is formed because of photosynthetic (parenchyma) cells. Mesophyll generally consists of big and highly vacuolated cells along with chloroplasts. Spongy Mesophyll and palisade parenchyma are also a part of this tissue.
Option D: Water channel: The bundle of 6 transmembrane a-helices forms Aquaporin proteins which are embedded in the cell membrane and it consists of amino & carboxyl at its end faces inside the cell. It is also known as water channels as it is a protein channel of a major intrinsic protein which forms the pores of a membrane inside a biological cell and helps in transportation of water in between the cells.

Hence, the correct answer is option (B).

Note: The endodermis layer helps to prevent water or any kind of solutes presents water from passing through the endodermis layer via the apoplast pathway. Water can only pass through the endodermis layer twice, once it crosses the membrane of the endodermal cells and second while existing the membrane of the endodermal cells. This layer does not allow the gas bubbles to enter the xylem so as to prevent water columns from embolisms.