Secondary growth in plant roots

Plant Anatomy, Botany presentation on secondary growth of roots

1. SECONDARY GROWTH IN ROOTS BY PRANJAL DHAKA 2042

2. CONTENT Why we need secondary growth? Anatomy of dicot roots. Process of secondary growth.

3. Why need it? 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.

4. ANATOMY OF DICOT ROOT 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.

5. ANATOMY OF DICOT ROOT 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 metaxylem towards the center. Pith: Not very prominent. B undle of parenchymatous tissue.

6. PROCESS OF SECONDARY GROWTH

7. THE CAMBIAL RING It is wavy in the beginning unlike in dicot stems. The cambial ring is completely secondary in origin.

8. SECONDARY VASCULAR TISSUE

9. FUNCTIONS OF SECONDARY XYLEM 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

10. FUNCTIONS OF SECONDARY PHLOEM 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

11. EXTRA-STELAR SECONDARY GROWTH Roots can also form the exact kind of periderm by the process of seconary growth. The cork cambium cuts off the phelloderm inside of it, composed of living parenchymatous tissue. It cuts off phellem (cork) on the outside of it.

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