Anatomy of Cycas Root and Coralloid Root

Part – 3: Anatomy of Normal and Coralloid Root
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Cycas Anatomy of Tap-Root

Ø  The primary anatomical structure of Cycas tap-root resemble that of dicot root

Ø  The T.S. is circular in outline.

Ø  Anatomically the tap-root is differentiated into FOUR regions.

(1). Epiblema (Epidermis)

Ø  The outermost layer,

Ø  Cells are parenchymatous and single-layered

Ø  Contain plenty of root hairs for the absorption of water and minerals

(2). Cortex

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Ø  Cortex is located inner to the epidermis.

Ø  Composed of multilayered parenchymatous cells.

Ø  Cortical cells are loosely arranged with plenty of intercellular spaces.

Ø  Cell contain plenty of starch grains as deposition

Ø  Few tannins cells are also present in the cortex.

(3). Endodermis and Pericycle

Ø  Endodermis is single-layered and inconspicuous.

Ø  Pericycle usually multilayered.

cycas root record diagram

(4). Central stele

Ø  The stele is located inner to pericycle in the centre.

Ø  Vascular bundles radial and diarch

Ø  Diarch: Two xylem and phloem strands alternatively arranged.

Ø  Xylem is exarch (protoxylem directed towards the exterior)

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Ø  Secondary thickening occurs in the tap-root.

Ø  Secondary thickening is similar to the dicot roots

Ø  A continuous ring of cambium is differentiated it cuts secondary xylem towards the inner side and secondary phloem towards the outer side.

Ø  Periderm formation also occurs in mature tap-root as usual.

Learn more: Difference between Coralloid Root and Tap-Root in Cycas

Anatomy of Coralloid Roots

Ø  Coralloid roots are a special type of negatively geotropic, highly branched and symbiotic root found in Cycas. (See Morphology of Cycas for details.)

Ø  The anatomy of the coralloid root is more or less similar to the normal root (tap-root)

Ø  Anatomically it is differentiated into:

(1). Epiblema

(2). Cortex

(3). Vascular Tissue

(1). Epiblema (Epidermis)

Ø  The outermost layer

Ø  Cells are parenchymatous and single-layered

Ø  Root hairs are ABSENT in the epidermis

(2). Cortex

Ø  Cortex is located inner to the epidermis.

Ø  Cortex is large and differentiated into THREE zones

(a). Outer Corte

(b). Middle Cortex

(c). Inner Cortex

Ø  Cells of the cortex are parenchymatous and loosely packed with plenty of inter-cellular spaces.

Ø  The middle zone of the cortex is called ALGAL Zone.

Ø  In the algal zone, the cortical cells (single layer) are radially elongated.

Ø  Blue-green algae (Anabaena cycadae) occur endophytically in the middle layer of the cortex.

Cycas Coralloid Root Diagram

coralloid root record diagram

Ø  These algae in the algal zone are symbiotic.

Ø  They help in nitrogen fixation.

Ø  The endodermis is single-layered and it separate stele from the cortex.

Ø  Pericycle multilayered and prominent.

(3). Vascular Tissue

Ø  Vascular tissue is located in the central region of the root

Ø  Vascular bundles are Radial and Triach

Ø  Triarch: Three traces of xylem and phloem arranged alternatively

Ø  The xylem exarch (protoxylem is located towards the periphery)

Ø  Pith is usually absent, very small if present.

Ø  Secondary thickening usually absent in coralloid roots.

Learn more: Difference between Coralloid Root and Tap-Root in Cycas

<<< Cycas Part 2: Stem Anatomy          Cycas Part 4: Rachis and Leaf-let Anatomy >>>

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