Underground Organs in Plants PDF

# SUBTERRANEAN ORGANS = UNDERGROUND ORGANS - **Definition:** - Subterranean or underground organs are those parts of the plant that grow under the ground. - They are of root or stem origin. - **Stem structures** such as: corms, bulbs, stem-tubers and rhizomes. - **Root structures** such as...

# SUBTERRANEAN ORGANS = UNDERGROUND ORGANS - **Definition:** - Subterranean or underground organs are those parts of the plant that grow under the ground. - They are of root or stem origin. - **Stem structures** such as: corms, bulbs, stem-tubers and rhizomes. - **Root structures** such as: true, adventitious roots, and root-tubers. - **Types of Underground Organs** | Underground stems | Roots | | ------------------------------ | ------------------------ | | Rhizomes | True root | | Corms | Adventitious roots | | Stem tuber | Root tubers | | Bulbs | | | Stolons | | # Characteristics of Underground Organs: - Subterranean organs are characterized by the absence of chlorophyll. - Root and rhizomes superficially are similar in size and appearance, there is no clear division between them. - Commercial rhizomes always contain a considerable proportion of root and similarly, commercial root consists of a rhizome at its upper part. - Subterranean organs which are used in medicine are collected from perennial plants where they serve as storage organs so they are rich in reserve food materials. - They are rich in carbohydrate compounds, for example: - Starch which is abundant and of common occurrence e.g. Ginger and Rhubarb. - Sugars: e.g. in Gentian - Inulin: e.g. family Compositae # Differences between subterranean stems and roots from outside and inside: | Characters | Subterranean stem | Root | | --------------------- | ------------------------------------------------------------ | --------------------------------------- | | Outside | | | | Nodes & internodes | There is nodes & internodes either long or short. | No nodes or internodes. | | Scale leaves & | Scale leaves, axillary buds & adventitious roots (all are | No scale leaves or axillary buds. | | axillary buds | arising at nodes). | | | Wrinkles | Mainly transverse. | Mainly longitudinal. | | Inside | | | | Pith | There is wide pith in the center. | No pith, there is a solid mass of xylem vessels. | | Pericycle | Pericycle is present. | Pericycle is absent. | # THE ROOT ## 1- Definition - The root is that part of the plant axis, which grows vertically downwards into the soil away from light. - It does not show nodes and internodes. - It does not bear leaves or buds. - Its growing point is covered with a special tissue called the root cap. ## 2- Branching - The root bears only one kind of lateral branches which are similar in general characters and in structure to the main root. - The origin of the branches is described as endogenous, because the growing point arises in the outer most layer of the stele, in the pericycle. ## 3- The root system - It develops as a result of the growth of the radicle, producing primary root. - In dicot: Persists and give tape root system. - In monocot: The primary root stops growing and numerous roots arise from the stem producing fibrous root system. ## 4- Composition of the root - The root is generally constructed of four zones: - The growing point - The zone of elongation - The zone of root hairs - The zone of lateral branches # Functions of the root - Absorption of water, soluble minerals and organic compounds from the soil and transformation of them to the stem. - It anchors the plant to the ground. - As a storage organ and for propagation. # Types of the Roots - **Primary roots:** They are developing into tap roots, as in Senega, Belladonna. - **Secondary roots:** They are the lateral roots, as in Krameria. - **Adventitious roots:** They arise from the stem, as in Ipecacuanha. - **Storage roots:** they are the roots of any of the previously mentioned types, which become swollen with reserve food materials, e.g.: - Swollen primary roots: Belladonna - Swollen secondary roots: Asafoetida - Swollen adventitious roots: Calumba - **Tuberous roots:** those which are very swollen, e.g. Jalap. # HISTOLOGY OF THE ROOT (DICOT. PLANTS) ## Histology of the young root (primary root) - The young dicotyledons root is histologically characterized by the following tissues: - **Piliferous layer:** single row of thin walled cells showing no stomata, no cuticle and no intercellular spaces, the cells bear root hairs. - **Cortex:** It is wide and parenchymatous. - **Endodermis:** The inner most layer of cortex is distinct of a single row of small cells. They have either thin outer tangential walls and other thickened ones or lignified. - **Stele:** Is central and formed of a single or many-layered pericycle enclosing the vascular bundles which are radial formed of alternating groups of phloem and xylem. - **There is no cambium at all in the very young root**. - **The pith is lacking in woody dicotyledons**, where the central part is occupied by metaxylem elements, but is **present in monocotyledons**, represented by thickened parenchyma or sclerenchyma. - **The xylem occurs in radial groups or arches with the protoxylem directed outwards**, i.e. exarch # Secondary Thickening in the Dicot root - The root of the monocotyledons usually retain their primary structure, but in the dicotyledons, secondary thickening takes place as follows: - **The cambium originates in the parenchyma below the phloem groups then in the pericycle outside the protoxylem forming stellate or wavy ring.** - **Cambium gives to the inside secondary xyllary tissue and to outside secondary phloem tissue.** - In the later stage the cambium becoming circular in form. - Opposite each protoxylem group, the cambium produces medullary rays. - Phellogen is developed in the pericyclic region giving cork to the outside and phelloderm (secondary cortex) to the inside. # WOOD ## A- Wood Fibres It consists of secondary xylem which enclose in the centre a very small amount of primary xylem. The elements of the wood are: Fibres, tracheids, vessels, tracheidal vessels, wood parenchyma and medullary rays, all have thick wall cells and lignified. - Single, non living, very elongated cell, having very long tapering ends, thick lignified, pitted walls and narrow lumen. - When the fibre being living and retaining some of the cell contents as starch, but with lignified walls called substitute fibre - When the fibre show a partitions at intervals called septate fibre. ## Tracheids and Tracheidal Vessels - **Tracheids:** Water conducting elements and serve for support: It is elongated cell with bluntly tapering but not sharply pointed ends, the walls are lignified thickened, pitted. - **Tracheidal vessels:** Similar to tracheids but the end wall showing one perforation ## Vessels - Conducting tubes, formed from number of cells placed end to end by the partial disintegration of their end walls, showing perforations at both ends. # RADIX GLYCYRRHIZAE (Syn: Liquorice, Glycyrrhizae, Sweet wood, Erqusous) ## ROOTS Official Roots In E.Ρ. - **Origin:** - The dried peeled or unpeeled root and rhizome of Glycyrrhiza glabra variety typica known as Spanish Liquorice. Family Leguminosae - G. sources grow in Spain, France, England, Italy, Germany and USA. # Collection and preparation: - Three years after cultivation: - The underground organs are dug-up, washed and cut into short pieces. - Rootlets and buds are removed. - The roots and rhizomes (stolons) are dried rapidly in the sun and finally in a heated chamber. - **Stolon:** They are horizontal underground stems (run nearer the surface) which can produce new plant from their nodes e.g. in liquorices. The principal root divides into several branches which penetrate the soil to a depth of 1 meter or more. # Spanish liquorice - It consists of stolons with few pieces of roots. - **Shape:** cylindrical in shape, unbranched - **Colour:** the unpeeled is dark brown or reddish- brown. The peeled is yellow. - **Stolon:** bearing small buds, scaly leaves and scars of slender side roots. - **Root:** bearing small rootlet scars. - **The Liquorice has very sweet taste in peeled L. and sweet at first followed by bitterness in unpeeled one. Why?** - **Fracture is fibrous, internally is bright yellow.** # Microscopical characters - Rhizomes and roots of Liquorice have typical structure except: - The absence of pith and pericycle in the root. - the presence of the tetrarch primary xylem in the center of the root. - **A transverse section in the rhizome shows the following layers:** - **Cork:** formed of several layers of brown flattened polygonal, thin-walled cells - **phelloderm:** narrow, formed of parenchyma cells containing isolated prisms of calcium oxalate and simple starch granules - **Pericycle:** it is parenchymatous with small groups of fibres at intervals. - **Phloem:** it is wide, yellow and composed of: - groups of lignified fibres, each group is surrounded by a sheath of parenchymatous cells, each usually contain a prism of calcium oxalate forming a "crystal sheath". - sieve tissue consists of sieve tubes companion cells and phloem parenchyma. The phloem is traversed by numerous wavy funnel-shaped m.r. - **Cambium:** is an incomplete line composed of about 3 layers of flattened cells. - **Secondary xylem:** is composed of vessels, wood fibres and wood parenchyma. - The vessels show reticulate or pitted walls, the pits are bordered with slit-like opening. - wood fibres resembling the phloem fibres in form and in being enclosed in a crystal sheath. The wood parenchyma has lignified pitted walls. - **Medullary rays:** They are 3-5 cells being wide in the xylem and becoming funnel-shaped in the phloem. - **Pith:** present only in the rhizome, dark yellow and parenchymatous. - **Root with 4 arch primary xylem**, but no pith. In the peeled liquorice the cork, cortex and sometimes part of phloem are absent. - **Starch granules** are simple, small, spherical to ovoid, a slit-shaped hilum is visible in some of the larger granules. # Powder - **Light-yellow in colour in the peeled, brownish-yellow in the unpeeled.** - **It has a faint characteristic odour and very sweetish taste.** - **Microscopically**, it is characterised by the following fragments: - **Numerous starch granules, free or in parenchyma cells, mostly simple, oval, rounded, with no striations but occasionally showing a slit-shaped hilum in some of the larger granules.** Compound granules are present with two, three or four components. - **Prismatic crystals of calcium oxalate, free or in cells.** - **Cork cells:** consisting of polygonal thin-walled cells in surface view with brown contents. - **Fibres which occur in groups surrounded by a calcium oxalate prisms sheath.** Individual fibres are very thick-walled, narrow lumen, acute apex with few small pits. - **The vessels, which are found singly or in small groups**, some of the individual vessels are very large and are frequently found fragmented. They are usually bordered pitted. - **Fibres of pericycle, phloem and xylem -vessels - wood parenchyma and medullary ray cells.** # Active constituents - **Triterpenoidal saponins:** glycyrrhizin about 5-7% (saponin like glycoside). It is the potassium and calcium salt of glycyrrhizinic acid, which is 50 times as sweet as sugar. Upon hydrolysis the glycoside loses its sweet taste and is converted to the glycyrrhetic acid plus 2 molecules of glucuronic acid. - **glycyrrhein** (Very sweet taste, Hydrolysis - glycyrrhetic acid (Loss the sweet taste) + 2 molecule of glucuronic acid. _The sweet taste of liquorice is due to --?_ # Uses - **Expectorant:** It is an ingredient in cough medicine (it loosens and thins mucous) [B-well syrup liqu. Thyme], [Broncare liqu. Thyme and fennel] - **Demulcent:** it relives internal inflammation of membranes. - **Antiulcerogenic activity:** used in treatment of stomach and deudenal ulcers. - **Glycyrrhetic acid has deoxycorticosterone effect so it is used in treatment of rheumatoid arthritis**, Some inflammatory conditions and in addison's disease Chronic adrenocortical insufficiency). - **Flavonoid components possesses antimicrobial and antiviral activity (externally in the form Gel).** - **Glycyrrhetic acid has hormonal activity as estrogenic action so used as starting material for semisynthesis of cortisone and sex hormones.** - **Prevent liver toxicity** How? - Protect the liver through its memberane stabilization effect - Stop viral C multiplication inside the liver cells. - Induce the production of self-interferon # There are two types of liquorice: - **"standard" liquorice** - **"De-glycyrrhizinated" liquorice (DGL).** - When glycyrrhizin is removed from liquorice, the product is called deglycyrrhizinated liquorice or DGL. - Each type is suitable for different conditionss # Uses - **Expectorant**: liquorice is effective expectorant, helping to liquefy mucus and facilitate its discharge from the body.It is an ingredient in cough medicine B-well syrup (liquorice, Thyme) Broncare (liquorice, Thyme and fennel) - **Demulcent**: it relives internal inflammation of membranes. - **Hyperacidity**:liquorice is also considered as an excellent remedy for hyperacidity. It removes the irritating effects of acids in a better way than alkalis. # Antiulcerogenic activity: - Deglycyrrhizinated liquorice or DGL. This product is especially useful in treating stomach and deudenal ulcers of the digestive tract because of the flavonoids, which are not harmed by the removal of glycyrrhizin. - The flavonoids have been known to kill Helicobacter pylori, the bacteria that cause most ulcers and inflammations of the stomach. # Deoxycorticosterone effect: - glycyrrhizin Its action is similar to hormones produced in the adrenal cortex, especially desoxycorticosterone, so it is used in treatment of rheumatoid arthritis, some inflammatory conditions and in addison's disease (chronic adrenocortical insufficiency) # Antimicrobial and antiviral activity: - Flavonoid components possesses antimicrobial and antiviral activity (externally in the form Gel). # Side Effects and Contraindications: - **Side Effects:** - Excessive consumption of liquorice and its ingredient glycyrrhizin causes 'mineralocorticoid syndrome'. - Symptoms include: - Water and sodium retention this lead to high blood pressure. - Loss of potassium this lead to heart irregularities - **Contra-indications:** - should not be used in: - Hypertensive patients - Current use of digitalis peparation (lanoxin) - During pregnancy and lactation - During corticosteroid treatment - Liquorice products should not be used for longer than four to six weeks. - **Deglycyrrhizinated extracts are free of adverse mineralocorticoid side effects.**