Anatomy of the Dicotyledonous Root
The dicotyledonous root is one of the clearest places to learn plant anatomy. A transverse section of a mature sunflower root shows concentric layers of tissue, each with a defined role: water and minerals move inward while sugars move outward.
This quiz follows that slice layer by layer — from the epiblema and its unicellular root hairs, through the parenchymatous cortex, past the suberin-lined casparian strips of the endodermis, into the pericycle, the conjunctive tissue, and the alternating xylem and phloem patches, ending at the small pith.
What you will practise
- Identifying each layer and its cellular character
- Explaining the radial arrangement of xylem and phloem
- Locating the origin of lateral roots and the vascular cambium
- Defining the stele as all tissues inside the endodermis
Work carefully: the terminology is cumulative, and each structure earns its place in the sequence.
Q1. In a transverse section of the sunflower root, which tissue forms the outermost layer?
The outermost layer of the dicot root is the epiblema, and many of its cells protrude as unicellular root hairs.
Q2. The root hairs of the dicot root are best described as:
Many cells of the epiblema protrude in the form of unicellular root hairs, which are extensions of individual cells.
Q3. Which feature correctly describes the cortex of the dicotyledonous root?
The cortex consists of several layers of thin-walled parenchyma cells with intercellular spaces.
Q4. The innermost layer of the cortex is called the:
The innermost layer of the cortex is the endodermis, a single layer of barrel-shaped cells without intercellular spaces.
Q5. Which statement about the endodermis of the dicot root is correct?
The endodermis comprises a single layer of barrel-shaped cells without any intercellular spaces.
Q6. The casparian strips of the endodermal cells are formed by deposition of:
The tangential and radial walls of endodermal cells have a deposition of water-impermeable, waxy material suberin in the form of casparian strips.
Q7. On which walls of the endodermal cells are casparian strips deposited?
The tangential as well as radial walls of the endodermal cells bear the suberin deposition forming casparian strips.
Q8. The pericycle of the dicot root is described as:
Next to the endodermis lies a few layers of thick-walled parenchymatous cells referred to as the pericycle.
Q9. Initiation of lateral roots and of the vascular cambium during secondary growth takes place in the:
Initiation of lateral roots and vascular cambium during secondary growth takes place in the pericycle cells.
Q10. The parenchymatous cells lying between the xylem and the phloem in the dicot root are called:
The parenchymatous cells which lie between the xylem and the phloem are called conjunctive tissue.
Q11. How many xylem and phloem patches are usually found in the dicot root?
There are usually two to four xylem and phloem patches in the dicot root.
Q12. In the dicot root, the arrangement in which xylem and phloem lie alternately on different radii is called:
When xylem and phloem within a vascular bundle are arranged alternately along different radii, the arrangement is called radial, as in roots.
Q13. During secondary growth of the dicot root, a cambium ring develops:
Later, a cambium ring develops between the xylem and phloem in the dicot root.
Q14. The stele of the dicot root includes all tissues:
All tissues on the inner side of the endodermis, such as pericycle, vascular bundles and pith, constitute the stele.
Q15. Which of the following is a correct description of the pith in the dicotyledonous root?
In the dicot root the pith is small or inconspicuous, unlike the large, well-developed pith of the monocot root.