Subterranean Organs

Pharmacognosy III

1. Subterranean Organs Prepared By Mona Ismail Pharmacognosy Department, Faculty of Pharmacy, Beni-Suef Universuty Pharmacognosy III Lab 1

2. Subterranean Organs Organs that grow under the ground or near the soil. They serve as storage organs for the plant, so they are full of reserved food materials such as starch, inulin and sugars (Carbohydrate). They are devoid of chlorophyll.

3. Subterranean roots Subterranean stems Subterranean Organs Rhizomes Corms Bulb Stem Tuber Root Root Tuber Classification according to their origin

4. A- Subterranean Stems These are characterized by: Externally: 1- Scaly leaves 2- Axillary buds (in the axis of scaly leaves) 3- Adventitious roots 4- A growing point protected by scale leaves forming a bud. Internally: Never having solid central xylem. In dicots there are central parenchymatous pith.

5. B- Subterranean roots The root is that portion of the plant axis which in the seedlings grows vertically downwards in the soil. It doesn’t show nodes and doesn’t bear leaves or buds . Its growing point is covered by a special tissue called ‘root cap’ usually darker in color and slimy to facilitate penetration in the soil . It bears lateral appendages(Secondary root) originated from the pericycle (rootlets) that are similar in structure to the main root but thinner and less strong. (Secondary root)

6. 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

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

8. 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

9. Monocot stem Dicot stem

10. Cambium present Cambium absent Xylem inside Phloem outside Xylem outside Phloem inside

11. Amphicribral ( Vasocentric ) Amphivasal

12. Subterranean roots Subterranean stems Subterranean Organs Rhizomes Corms Bulb Stem Tuber Root Root Tuber Classification according to their origin

13. 1 -Rhizomes: The most important group. Underground stem with nodes and internodes, long or short, terminal buds and aerial shoots. They grow horizontally with roots on the lower side and scale leaves and aerial shoots on the upper side Sometimes grow vertically with the roots and scale leaves all over the surface Lower side Upper side

14. 1.1- Stolon: Underground stem which travels near or above the surface of the soil. Horizontally growing. Produce new shoots and roots New Root New Shoot

15. 1.2- Sucker: A type of rhizome which is a branch of the main stem or top of root Growing under the ground, arising from the stem or from the top of the roots and giving off roots and aerial shoots at the nodes.

16. 2-The Corm: is a shortened swollen erect underground stem, covered with a brown scaly leaves arising at the nodes and having usually a large apical bud and small axillary ones. (e.g. Colchicum, Colcasia ).

17. 3-The Stem Tuber: Swollen underground stem differing from the root tuber in bearing several small scales and buds (called eyes) as well as a terminal bud in the free end (e.g. Potato) . It is full of food material and serve for vegetative propagation. It differ from root tuber in: 1- Bearing small scales and buds forming what is called eyes 2- Terminal buds on the free end as in potato

18. 4 -The Bulb: is an underground stem which is reduced to a small flat disc and is crowned with crowded fleshy scaly leaves or scaly leaf -bases and having adventitious roots arising from the base of the bulb. It may be: -Imbricate-bulb (each leaf base is covered with a scaly sheath, without a complete scaly cover) e.g. Lilium & Garlic. -Tunicate-bulb (with outer scales completely enclosing the inner fleshy ones e.g. Squill & Onion.

19. Internal Structure of stem Stem formed of the following layers:- 1- Epidermis 2- Cortex 3- Cambium 4- Phloem 5- Xylem 6- Pith

20. B- Subterranean roots The root is that portion of the plant axis which in the seedlings grows vertically downwards in the soil. It doesn’t show nodes and doesn’t bear leaves or buds . Its growing point is covered by a special tissue called ‘root cap’ usually darker in color and slimy to facilitate penetration in the soil . It bears lateral appendages(Secondary root) originated from the pericycle (rootlets) that are similar in structure to the main root but thinner and less strong. (Secondary root)

21. Four zones of Roots 1- Growing point covered by root cap & help root to penetrate soil particle. 2- Zone of Elongation is free of any outgrowth increase the length of the root. 3- Zone of Absorption (Zone of root hair). 4- Zone of lateral branches (occupy the majority of the root)

22. Types of Roots 1- Primary Roots: which develop as tap roots 2- Secondary roots: which are the lateral roots

23. 3- Adventitious roots: don’t arise from either the main root or from its branch, arising from the stem (rhizomes) as in Ipecacuanha .

24. 4- Storage roots: any of the previous types if swollen with reserved food material form storage root. Very swollen roots are called Root Tubers ( Jalap, Aconite ). Sweet Potato Carrots

25. Internal Structure of Root 1- Epidermis: Outer layer of cells (protection). 2- Root hair: An extension of specialized root epidermal cells (increasing area for absorption of water & minerals). 3- Cortex: Region between epidermis & vascular cylinder (supports plant parts & stores food). 4- Endodermis: Layer of cell just outside vascular cylinder. 5- Pericycle : Cylindrical layer of cells inside endodermis (origin of cork & secondary root ) .

26. 6- Vascular cylinder : Arrangement of vascular tissues as central cylinder in roots. This is shown as the large circular area in the middle. A- Xylem: Vascular system carrying water & minerals throughout plant. B- Phloem: Vascular system carrying dissolved sugars & organic compounds throughout plant . C- Cambium: Form continuous stellate ring, it gives 2ry phloem to outside & 2ry xylem to inside.

27. Root Diagram