Lecture 6: Root and Shoot Systems PDF

Faculty of Pharmacy and Biotechnology Pharmaceutical Biology Department Pharmacognosy I (PHBL 303) Lecture 6 Root and Shoot Systems Associate Prof. Heba Handoussa Head of Pharmaceutical Biology Department He...

Faculty of Pharmacy and Biotechnology Pharmaceutical Biology Department Pharmacognosy I (PHBL 303) Lecture 6 Root and Shoot Systems Associate Prof. Heba Handoussa Head of Pharmaceutical Biology Department [email protected] Office: B5.130 Office hrs: Sunday 4th and Monday 2nd slots 1 Intended Learning Outcomes Domain 1: Fundamental Knowledge 1-1 Competency Key Elements 1 Describe the structure and function of the plant cells. 2 Articulate knowledge about the different types of plant tissues, and their functions. Domain 2: Professional & Ethical Practice 1 Competency Key Elements 1 Categorize plant species through describing uses 2 Relate the presence or absence of a certain plant features to the prevalent Environmental conditions. 2 Competency Key Elements 1 Identify the uses of each taxonomical group to which a plant belongs. Domain 3: Pharmaceutical Care 2 Competency Key Elements 1 Relate available information on taxonomical data to the potential presence of natural products. Domain 4: Personal Practice 1 Competency Key Elements 1 Develop the ability to think creatively and understand scientific principles. 2 Competency Key Elements 1 Communicate scientific information in a clear and concise manner both orally and Written. 3 Competency Key Elements 1 Practice independent learning required to build up knowledge base. 2  Root and Shoot Systems A) The plant body: The plant body is composed of 2 main parts (systems): 1 Shoot system (stems, leaves, flowers and fruits): It grows above the ground seeking light and air. 2 Root system (primary root and lateral roots): It grows under the ground. 3 B) The plant organs: The plant body consists of 3 main organs: 1) Root 2) Stem 3) Leaf 4 B) The plant organs: 1) Root: It is the underground part of the plant. It has several functions: 1) Fixing the plant firmly in the soil. 2) Absorbing water and nutrients from the soil. 3) Storage of food material to be used as a reserve (in case of exposure to harsh conditions and to protect them from external predators). 5 B) The plant organs: 2) Stem: It grows usually above the ground. It has several functions: 1) Supporting and holding the leaves. 2) Holding flowers and seeds (used for reproduction). 3) Transporting water and nutrients from root to leaves. 6 B) The plant organs: 3) Leaves (energy factories): They have several functions: Their main role is to use sunlight and carbon dioxide for photosynthesis (producing food for the plant). Transpiration. Gas exchange. 7 C) The plant tissues: Each organ has 3 types of tissues: 1) Boundary/Dermal. 2) Ground. 3) Vascular. 8 C) The plant tissues: 1) Boundary/Dermal (protective tissue): It is the outermost protective layer of the primary plant body. Derma means skin. Function: 1) Protect the internal tissues from mechanical injury and cover the plant. 2) Sometimes covered with a waxy layer called cuticle to protect from water loss. 3) Regulating the exchange of gases (in leaves). 4) Regulates absorption of water (in roots). 9 C) The plant tissues: 1) Boundary/Dermal tissue: A) Epidermis (Epidermal cells): They are irregular flattened polygonal living cells Epidermal cells of the stem have a cutin based covering the entire plant surface. They do not have chloroplasts. outermost layer known as cuticle making it waterproof, it protects the plant from water loss and infection. It has an inner most layer made of cellulose and A middle layer made of a mix of cellulose and cutin. 10 C) The plant tissues: 1) Boundary/Dermal tissue: B) Stomata and guard cells surrounding it: Stomata are very small pores in boundary tissue that open and close frequently. Stomata are highly abundant in leaves and are also found in stems. Function: water and gas exchange. Guard cells: are the pair of kidney-shaped cells surrounding the stomata. Function: they control the opening and closing of the stomata. 11 C) The plant tissues: 1) Boundary/Dermal tissue: C) Trichomes (hairs): Trichomes from the Greek trichoma meaning hair. They are elongated tubular outgrowths or appendages from the boundary tissues surrounding any plant organ (root, stem or leaf). They function differently according to their location in the plant: Trichomes in roots: They increase the surface area for absorption of water and minerals. Root trichomes do not have a waterproof cuticle. 12 C) The plant tissues: 1) Boundary/Dermal tissue: C) Trichomes (hairs): Trichomes in stems: These stem hairs act as a defense mechanism to deter chewing insects. (insects can not easily walk on hairs). They help prevent damage from frost, drought, hot climate and UV light. Trichomes in leaves: They help in modulation of water loss from leaves (prevent water loss during dry or windy conditions). These trichomes act via slowing the movement of air towards the leaf surface. They can be responsible for secretion of 13 essential oils (volatile oils). C) The plant tissues: 1) Boundary/Dermal tissue: C) Trichomes (hairs): Examples: 1) African violet (Saintpaulias sp.) has dense pointed trichomes on the leaf surface. The clear trichomes shown here contain chemicals that absorb UV light and act as a sunscreen. 2) Petunia (Petunia hybrida) has round-tipped trichomes filled with sticky substances that deter insects. 14 C) The plant tissues: 1) Boundary/Dermal tissue: C) Trichomes (hairs): Examples: 3) Sundew (Drosera sp.) are carnivorous plants. The red-tipped trichomes trap insects to the leaves. The sticky trichomes trap the insects and make enzymes that digest them, providing nitrogen to the plant. 15 C) The plant tissues: 1) Boundary/Dermal tissue: C) Trichomes (hairs): Trichomes produce different types of chemicals, often have been useful to humans. The chemicals provide flavors, have medicinal properties, or are used in household items. 16 2- Ground Tissue: It is the major plant tissue "filler" between the dermal tissue on the surface of plants and the vascular tissue in the middle. It is composed of different cell types: a- Parenchyma cells: It is the major plant tissue found in all types of plants. Basic packing tissue Unspecialized living cells Thin walled-plant cells (cellulose) They have large central vacuoles They are rich in chloroplasts Have intercellular spaces. Function: 1) Aid in photosynthesis. 2) Store nutrients and water (large vacuoles). 17 2- Ground Tissue: a. Parenchyma cells: 1) Chlorenchyma: Parenchyma with chlorophyll, tissue which contains chlorophyll pigment (chloroplasts). Helps in photosynthesis. 2) Aerenchyma: Parenchyma tissue with extensive connected air cavities in aquatic plants. Helps in floating and exchange of gases. 18 2- Ground Tissue: b- Collenchyma cells: Living cells Tissue responsible for flexibility in plants. Derived from the Greek kolla means glue. Supporting, strengthening and stretching tissue in young growing organs as stems and leaves. Irregularly thickened at corners, thickened by pectin. Less intercellular spaces. Function: Allows bending of stems, leaves without breaking. Provide mechanical support. 19 2- Ground Tissue: C- Sclerenchyma cells: Non-living cells. Tissue responsible for stiffness in plants. From the Greek word skleros meaning hard. Thickened cell walls made of cellulose impregnated with lignin. Simple pits are present in thickened cell walls. No intercellular spaces. Types of sclerenchyma cells: Fibers Sclereids Fibers: They are long, narrow, spindle-shaped and pitted. They are mainly present in xylem vessels. They have a narrow lumen. 20 2- Ground Tissue: C- Sclerenchyma cells: Sclereids: They are isodiametric, elongated, bone-shaped, star-shaped and stone shaped. Where are they found? Hard covering of seeds and nuts. Veins of leaves. Stem around vascular bundles. Function: Provides strength to plant parts. Provides mechanical support and protection to region that stopped growing and no longer need to be s flexible. 21 2- Ground Tissue: 22 C) The plant tissues: 3) Vascular/Conducting tissues: Vascular tissue is a complex conducting tissue, formed ofmore than one cell type. The primary components of vascular tissue are the xylem and phloem. Xylem and phloem are always found next to each other in a vascular bundle. 23 C) The plant tissues: 3) Vascular/Conducting tissues: A) Xylem: It is the tissue consisting of elongated cells that transports water from the root to other parts of the plant. It also provides strength and structural support to the stem because of their structure which is very thick, have rigid lignified secondary cell walls. Conducting elements present in xylem tissue are vessels and tracheids. There are other elements like xylem fibers and Parenchyma. (for mechanical support and storage). 24 C) The plant tissues: 3) Vascular/Conducting tissues: A) Xylem: Xylem tracheids are pointed, elongated xylem cells, the simplest of which have continuous primary cell walls and lignified secondary wall thickenings in the form of rings, hoops or reticulate networks (narrow and long). Vessels are hollow xylem cells aligned end-to-end, without end walls that are assembled into long continuous tubes (wide). 25 C) The plant tissues: 3) Vascular/Conducting tissues: A) Xylem: 26 C) The plant tissues: 3) Vascular/Conducting tissues: A) Xylem: 27 C) The plant tissues: 3) Vascular/Conducting tissues: B) Phloem: It is a specialized tissue for food conduction in higher plants. Phloem transports food and other organic substances synthesized by the leaves during photosynthesis to all the parts of the plant. It consists of several types of cells: sievetubes, companion cells, phloem parenchyma and phloem fibers. 1) Sieve tube element: They lack nuclei and ribosomes, and their metabolism and functions are regulated by the adjacent nucleated companion cells. Each sieve tube is formed by a series of hollow, cylindrical cells called sieve tube cells arranged one above the other. The sieve cells are separated from each other other 28 C) The plant tissues: 3) Vascular/Conducting tissues: B)Phloem: 2) Companion cells: The companion cells, connected to the sieve tubes via plasmodesmata, are responsible for loading the phloem with sugars. Each companion cell is found attached to any one lateral surface of a sieve cell. The companion cell has cytoplasm, prominent nucleus and one or two small vacuoles. The nucleus of the companion cell is said to be capable of exerting its influence on the adjacent sieve cells. 29 Root system: Root anatomy: The root is divided into 3 main zones: 1) Zone of Maturation (differentiation): Fully functional cells are present. Root hairs develop from epidermal cells to increase the surface area for the absorption of water. Cuticle exists on root but not on root hairs. 2) Zone of Elongation: It is the area where the root cells elongate and increase in length. 3) Zone of Cell Division (meristematic zone): It has cells that are continuously dividing through mitosis to make new cells leading to primary growth of the root (growth point). Protected by a root cap that protects the root as it forces its 30 way through the soil. Root system: Root anatomy: 31 Root system: Root anatomy: 32 Root system: Root anatomy: Monocot root Dicot root Number of xylem Polyarch xylem vessels Oligoarch xylem and phloem (more than 10 in vessels (3-5 in vessels (vascular number) number) bundle) Shape of xylem Circular Angular vessels Pith Wide Narrow or absent 33 Root system: Root anatomy: Dicot roots with narrow pith and absent pith 34 Types of Roots: 1 Fibrous roots (found mainly in Monocot plants): They are a mass of roots of equal size and diameter. They do not penetrate so deep in the soil. They consist of many branching roots that arise from the base of the stem. Examples: Grasses, wheat, rice 2- Taproots (Mainly in Dicot plants): The primary root is tall and thick and grows down from the stem. The secondary lateral roots are thin and small in size and number. It grows deep into the soil. Examples: Carrots, turnip 35 Types of Roots: 36 37