Question

Arrange the following structures based on their location from the periphery to centre with respect to the anatomy of a dicotyledonous root.
I. Pericycle
II. Casparian strips
III. Epiblema
IV. Conjunctive tissue

• A. IV, I, II, III
• B. IV, II, III,I
• C. I, II, III, IV
• D. III, II, I, IV

Answer 1

Answer: (D)

The outermost layer is epiblema. Many of the cells of epiblema protrude in the form of unicellular root hairs. The cortex consists of several layers of thin-walled parenchyma cells, with intercellular spaces. The innermost layer of the cortex is called endodermis. It comprises a single layer of barrel-shaped cells without any intercellular spaces. The tangential, as well as radial walls of the endodermal cells, have a deposition of water-impermeable, waxy material suberin in the form of casparian strips. Next to endodermis lies a few layers of thick-walled parenchymatous cells referred to as pericycle. Initiation of lateral roots and vascular cambium during the secondary growth takes place in these cells. The pith is small or inconspicuous. The parenchymatous cells which lie between the xylem and the phloem are called conjunctive tissue.