BY

PRANJAL DHAKA

2042

• Why we need secondary growth?

• Anatomy of dicot roots.

• Process of secondary growth.

• It increases the ability of plants to absorb water and facilitates transport of water and minerals in bulk quantities.

• Helps in mechanical support and anchoring when the tree grows big.

• Epiblema: Consists of the outermost epidermal layer with root hair arising from it.

• Cortex: Thin layer of parenchymatous layer. Main function is storage.

• Endodermis: Barrel shaped, rich in Starch and have radial and tangential thickenings called casparian bands due to lignin depositions.

• Pericycle: Made up of thin walled parenchyma cells. It gives rise to cork cambium, part of vascular cambium and all lateral roots.

• Vascular Strands: They are alternate bands of xylem and phloem. Protoxylem towards the periphery and metaxylemtowards the center.

• Pith: Not very prominent. Bundle of parenchymatous tissue.

• It is wavy in the beginning unlike in dicot stems.

• The cambial ring is completely secondary in origin.

• principle water-conducting tissue

• combination of vessels and tracheids

• primary xylem derived from procambium

• secondary xylem formed by vascular cambium

• wood made of accumulated secondary xylem

• principle food-conducting tissue in vascular plants, located toward the outer part of roots and stems

• carried out through sieve cells and sieve-tube members

• some sieve areas (pores) have larger pores called sieve plates

• each sieve-tube member associated with companion cell

• Roots can also form the exact kind of periderm by the process of seconary growth.

• The cork cambium cuts off the phelloderminside of it, composed of living parenchymatous tissue.

• It cuts off phellem (cork) on the outside of it.