T.S in Stem & Root Type of Vascular bundles

Pharmacognosy III

1. T.S in Stem & Root T ype of Vascular bundle Prepared By Mona Ismail Pharmacognosy Department, Faculty of Pharmacy, Beni-Suef University Pharmacognosy III Lab 1

2. Stem Root 1- Epidermis Outer layer of cells (protection) Outer layer of cells (protection), root hair (An extension of specialized root epidermal cells increasing area for absorption of water & minerals) 2- Cortex Region between epidermis & vascular cylinder (supports plant parts & stores food) 3- Endodermis Inner most layer of cortex ( Casperin strip or starch sheath or parenchyma) 4- Pericycle Outer tissue of stele ( pericycle + V.B + Pith) Peri = around, cycle= vascular bundle, it’s tissue outside the vascular bundles (origin of cork & secondary root) Histology

3. Stem Root 5- Phloem Vascular system carrying dissolved sugars & organic compounds (sap conduction) 6- Cambium Meristimatic tissue Disappear in young root . Old root: form continuous stellate ring, it gives 2ry phloem to outside & 2ry xylem to inside 7- Xylem Vascular system carrying water & minerals Vascular system carrying water & minerals (Center) 8- Pith Large central area for storage & support ----------------- V.B

4. Difference between Monocot and Dicot Stems Monocot Dicot 1- No. V.B Large number Limited number 2- V.B arrangement Scattered in the ground tissue Arranged in a ring 3- Cambium Absent Present 4- Cortex & Pith No distinction between cortex & pith The cortex & pith can be clearly distinguished 5- Secondary thickening No secondary thickening Secondary thickening occur 6- Annual rings No annual rings are formed Annual rings are formed due to secondary thickening

5. Monocot stem Dicot stem

6. Difference between Monocot and Dicot Roots Monocot Dicot 1- Type of V.B Radial Radial 2- No. V.B 8 or more ~ 4 3- Cambium Absent Present 4- Pith present Pith present in young root and disappear in old root due to secondary thickening of cambium appearance 5- Secondary thickening No secondary thickening Secondary thickening occur

7. Kinds of Stele: ( Pericycle + V.B + Pith ) 1- Protostele ( monostele ): primitive, simplest form, NO Pith . Stele is formed of xylem surrounded by phloem followed by pericycle surrounded by endodermis. 2- Siphonostele ( medullated protostele ) : Stele is formed of a central pith surrounded by a continuous ring of vascular bundle a. Ectophloic : phloem outside xylem. b. Amphiphloic : phloem on both sides of xylem (from inside- pith - phloem - xylem - phloem - endodermis) c . Dissected siphonostele [ Eustele ] : Siphonostele is broken up to give ring of separate vascular strands. Most common type in dicots . 3- Actatostele : dispersed vascular strands, in Monocots. A B C 3

8. Cambium present Cambium absent Xylem inside Phloem outside Xylem outside Phloem inside Always open

9. Amphicribral ( Vasocentric ) Amphivasal