Lecture 6- Medicinal Plants 2024/2025 (Mansoura National University) PDF

Medicinal plants 2024/2025 Lecture 6 Dr. Amal F. Soliman Dr. Walaa Safwat Associate Professor of Pharmacognosy Lecturer of Pharmacognosy  A B ▪ Which of them (A or B) is the...

Medicinal plants 2024/2025 Lecture 6 Dr. Amal F. Soliman Dr. Walaa Safwat Associate Professor of Pharmacognosy Lecturer of Pharmacognosy  A B ▪ Which of them (A or B) is the dicot stem and which is the monocot stem? Please explain your answer. ▪ In A, why the vascular bundle is composed of phloem and xylem ? And in B, the vascular bundle is composed of phloem, cambium, xylem ? ▪ Is it a dicot leaf or monocot leaf ? Please explain your answer. Today's lecture Secondary thickening/Growth ▪ Occurs in most of the dicot roots & stems. ▪ It increases the diameter of the organs by the activity of the vascular cambium and the cork cambium (Lateral Meristems).  Secondary growth in the stem 1- Formation of interfascicular cambium so cambium has the shape of continuous ring. 2- The cambium produces secondary xylem to the inside and secondary phloem to the outside. These rings of xylem and phloem are traversed by MRs (medullary rays). 3- Periderm usually arises in the subepidermal cortex. Parenchyma cells become meristematic and form a Cork Cambium or Phellogen.This produces Cork Cells or Phellem to the outside. ❑ Periderm consists of three parts: phellogen (cork cambium), the phellem (cork) and the phelloderm (secondary cortex). ❑ Suberin (a wax) is secreted into the walls of the Cork Cells. This makes them waterproof and pathogen-proof. Lenticels o When the epidermis is lost by the formation of periderm, the passage of gases through the stomata can no longer takes place, So the lenticels arise beneath the stomata and at an early stage of development of the periderm.  Short summary  Annual rings ▪ In spring, when a new branches and leaves are being formed, water conducting elements are developed wider than in the following season (early or spring wood). ▪ The wood formed later in the season, in summer or in early autumn is called (late, summer or autumn wood). ▪ No line exits between the two parts of a ring but there is a sharp line between the late wood of one year and the early wood of the next year. ▪ Concentric zones or rings which may be served as a mean for counting the age of plant. ▪ An annual ring therefore consists of two parts, an inner layer is the spring wood and an outer (darker layer) is the summer Wood. ▪ The annual rings can be visible even to naked eye and serve as a mean of counting the age of the plant.  Secondary growth in the dicot root ‫لالطالع فقط‬ 1- The cambium appears at first as a number of disconnected concave arcs. 2- The pericyclic cells become meristematic, thus united the separate arcs of cambium into a continuous band running between the primary xylem and the primary phloem.  ‫لالطالع فقط‬ 3- The concave arcs of cambium move outwards, carrying the phloem with them to form a perfect circle. 4- The cambium divided producing secondary xylem to the inside and secondary phloem to the outside. 5- Formation of cork. ‫لالطالع فقط‬ ‫لالطالع فقط‬  Sapwood and heartwood ▪ In most woody plants, the vessels remain functional only for a few years after their formation, and frequently for one year. This conducting wood is known as sap wood. When conduction ceases, it is termed heart wood. The vessels of heart wood are often filled with substances which render it darker. These substances preserve the wood from decay and make it more resistant to microbial attack than sap wood. Tyloses Tyloses ▪ The cavities of vessels in heart wood are blocked by balloon-like structures from adjacent living wood parenchyma, called tyloses. ▪ Tyloses are the enlarged protrusions of the pit membranes of the half- bordered pits from a living parenchyma cell into a vessel or a tracheid lumen.  ‫أجزاء المنهج‬ ❑ Anatomy (Lectures 1, 2, 3, 4, 5) ❑ Taxonomy ‫احملارضة القادمة ان شاء هللا‬ ❑ Physiology ❑ Dusting powders ❑ Introduction to Pharmacognosy Choose * Xylem and phloem are: a- Ground tissues b- Conducting tissues c- Secretory tissues d- Meristematic tissues * Chloroplasts are responsible for the process: a- Nutrition b- Absorption c- Ion exchange d- Photosynthesis * Xylem arrangement in roots are called: a- Endarch xylem b- Exarch xylem c- Mesoarch xylem d- Proarch xylem * Lenticels are structures formed to replace the function of: a- Cork b- Stomata c- Epidermis d- Hairs * Annual rings can be counted in old stems due to formation of: a- Lenticels b- Spring and summer wood c- Periderm d- Secondary cortex * Casparian strips of the endodermis are found in Monocot. Roots at: a- Radial walls b- Tangential walls c- Radial and inner tangential d- Outer tangential * Piliferous layer of roots are characterized by: a- Presence of stomata b- Absence of root hairs c- Absence of stomata and cuticle d- Presence of cork * Which of the following is a living tissue: a- Sclerides b- Vessels c- Cell wall d- Epidermis *The main function of sap wood is: a- Protection b- Conduction c- Storage d- Support * In Monocot. Leaves Vascular bundles usually are: a- Bicollateral b- Concentric c- Open collateral d- Closed collateral * The following starch is: a- Simple b- Compound c- Semi-compound d- All the previous answers * The main function of heart wood is: a- Support b- Protection c- Conduction d- Transmission * Radial vascular bundles are usually found in: a- Dicot stems b- Monocot leaves c- Dicot leaves d- Roots * Hydathodes are structures found in some plants to: a- Absorb water b- Exchange of gases c- Secret nectar d- Excrete water * The main function of glandular hairs is: a-Support b-Conduction c-Protection d-Secretion ▪ What is the type of this stomata ? ▪ what is the general function of stomata ? ▪ What is the type of starch granules? ▪ Mention the function of starch in plants? ▪ Mention one chemical test? ▪ The shown figure represents ………………………………………………. Give only the term corresponding to the following sentences: - The enlarged protrusions of the pit membranes of the half-bordered pits from a living parenchyma cell into a vessel or a tracheid lumen. A mean of counting the age of the plant. A group of loosely organized bark cells for gaseous exchange.