A dicot root, from outside to inside, has these layers: epidermis (epiblema), cortex, endodermis, pericycle, then the vascular tissue (xylem and phloem in a radial pattern), with a small pith at the centre. The xylem is exarch (protoxylem faces outward) and there are only two to four xylem groups, so it is diarch to tetrarch. Memory hook: "Every Cell Enjoys Peaceful Vascular Peace" = Epidermis, Cortex, Endodermis, Pericycle, Vascular, Pith.
Transverse section of a dicot root: epidermis, cortex and endodermis surround the pericycle; xylem (red, protoxylem outward = exarch) and phloem (green) alternate radially around a small central pith.
Your doubts, answered
What is the correct order of layers in a dicot root from outside to inside?
Start at the surface and move to the centre: epidermis (also called epiblema, with root hairs), then a wide multi-layered cortex of parenchyma, then a single-layered endodermis with Casparian strips, then the pericycle (a few layers, the seat of lateral roots and vascular cambium). Inside the pericycle sit the vascular tissues arranged radially, and a small pith may lie at the very centre. For NEET, remember the endodermis is the innermost layer of the cortex, and everything inside it (pericycle, vascular bundles, pith) forms the stele.
Is the xylem in a dicot root endarch or exarch?
It is exarch. Exarch means the protoxylem (first-formed, smaller xylem) lies towards the outside (periphery) and the metaxylem (later, larger xylem) lies towards the centre. Roots are exarch; stems are endarch (protoxylem towards the centre). NEET tests this directly, so link 'root = exarch' in your memory.
How many xylem groups does a dicot root have? Is it diarch or tetrarch?
A dicot root usually has two to four xylem groups, so it is described as diarch (2), triarch (3) or tetrarch (4). This is far fewer than a monocot root, which has more than six (polyarch). If a question shows 'polyarch' xylem, the answer is a monocot root, not a dicot root.
What tissue lies between the xylem and phloem in a dicot root?
Parenchyma cells lying between the xylem and phloem are called conjunctive tissue. In a dicot root, xylem and phloem sit on separate radii (radial arrangement), and the conjunctive parenchyma fills the space between them. During secondary growth, part of this conjunctive tissue below the phloem becomes the vascular cambium. This exact match (conjunctive tissue = tissue between xylem and phloem) appeared in NEET 2026.
Does a dicot root have a pith and how is it different from a monocot root?
A dicot root has only a small pith or almost none, because the few xylem groups often meet at the centre. A monocot root has a large, well-developed pith. So 'small or absent pith' points to a dicot root, while 'large pith' points to a monocot root.
⚠️ The NEET trap ✗ The xylem in a dicot root is endarch, like the dicot stem. ✓ The xylem in a dicot root is exarch (protoxylem outside, metaxylem inside). Only stems are endarch. 🧠 Root = exarch, Stem = endarch. NEET 2023 marked the statement 'endarch/exarch describe secondary xylem' as WRONG because these terms describe protoxylem position, and roots are exarch.
Real NEET questions
NEET 2019 (Odisha)
In the dicot root the vascular cambium originates from:
A · Tissue located below the phloem bundles and a portion of pericycle tissue above protoxylem ✓
B · Cortical region
C · Parenchyma between endodermis and pericycle
D · Intrafascicular and interfascicular tissue in a ring
Solution: In a dicot root the vascular cambium is completely secondary. It first appears as strips of conjunctive parenchyma just below (internal to) the phloem; later the pericycle cells above (external to) the protoxylem also become meristematic and join them to complete a wavy cambial ring. The pericycle is the seat of both lateral roots and the vascular cambium. Option D describes the dicot stem, not the root.
NEET 2026
Match List-I with List-II. A. Conjunctive tissue B. Casparian strips C. Subsidiary cells D. Starch sheath | I. Specialised cells near guard cells II. Endodermal cells rich in starch III. Tissue between xylem and phloem IV. Endodermal cells with suberin deposition
A · A-IV, B-III, C-I, D-II
B · A-III, B-IV, C-II, D-I
C · A-III, B-IV, C-I, D-II ✓
D · A-IV, B-III, C-II, D-I
Solution: Conjunctive tissue = parenchyma between xylem and phloem (III), a key dicot-root feature. Casparian strips = suberin deposition on endodermal walls (IV). Subsidiary cells = specialised epidermal cells near guard cells (I). Starch sheath = starch-rich endodermis of the dicot stem (II). This gives A-III, B-IV, C-I, D-II.
NEET 2018
Casparian strips occur in:
A · Cortex
B · Pericycle
C · Epidermis
D · Endodermis ✓
Solution: The endodermis is the innermost cortex layer of the root. Its cells have a band of water-impermeable suberin called the Casparian strip, which blocks the apoplast pathway and forces water through the cell membrane. The cortex, pericycle and epidermis do not have Casparian strips.
Solved Anatomy of Flowering Plants NEET PYQs
Try the real previous-year questions from this chapter — each with the answer and a full solution.
From outside to inside: epidermis (epiblema), cortex, endodermis, pericycle, radial vascular tissue (xylem and phloem), and a small pith at the centre.
Is a dicot root diarch or tetrarch?
A dicot root has two to four xylem groups, so it is diarch, triarch or tetrarch. Fewer than six xylem groups means dicot; more than six (polyarch) means monocot.
Why is dicot root xylem called exarch?
Because the protoxylem (first-formed xylem) lies towards the periphery and the metaxylem lies towards the centre. This outward protoxylem position is called exarch, and it is typical of all roots.
What is conjunctive tissue in a dicot root?
It is the parenchyma that lies between the separate xylem and phloem patches. Part of it later forms the vascular cambium during secondary growth.
Does a dicot root undergo secondary growth?
Yes. Unlike a monocot root, a dicot root forms a vascular cambium from conjunctive tissue and pericycle, allowing it to grow thicker over time.
