Plant Tissues, Roots, and Stems PDF

Plant tissues, Roots, and Stems Pharmaceutical Botany with Taxonomy (PBOT111) Patrick Joel F. Bicaldo, RPh, MSPharm (cand.) College of Pharmacy, Antipolo City Campus ver. PJFB24-25 1. The use of cellular phones is...

Plant tissues, Roots, and Stems Pharmaceutical Botany with Taxonomy (PBOT111) Patrick Joel F. Bicaldo, RPh, MSPharm (cand.) College of Pharmacy, Antipolo City Campus ver. PJFB24-25 1. The use of cellular phones is prohibited inside the classroom. 2. Taking pictures inside the classroom is not permitted. 3. Observe proper decorum during class discussions and activities. 4. Materials unrelated to the subject or the discussion must be placed inside the bag. LEARNING OBJECTIVES At the end of this module, the students should be able to: 1. Explain the morpho-anatomy of the different plant organs with their development, adaptations, modifications, and pharmaceutical importance 2. Describe features, functions, and composition of plant tissues and cell types. 3. Describe the roots, root system, root anatomy, functions, and importance of roots in the economy. Outline I. Plant Tissues II. Roots I. Internal and external structures II. Other root types and modification III. Stems I. Internal and external structures II. Other stem types and modifications Tillandsia straminea Thick Leaf Air Plant Opuntia spp. Prickly pear Introduction to Tissues and Primary Growth The relationships between plant organs, tissues, and cell types: Introduction to Tissues and Primary Growth Plant Body Organization Plants are multicellular eukaryotes whose bodies are composed of organs, tissues, and cells with highly specialized functions. The stems and leaves together make up the shoot system. Each organ (roots, stems, and leaves) includes all three tissue types (ground, vascular, and dermal). Different cell types comprise each tissue type, and the structure of each cell type influences the function of the tissue it comprises. Introduction to Tissues and Primary Growth Plant Body Organization Vascular plants have two distinct organ systems: Shoot system Generally grows above ground, where it absorbs the light needed for photosynthesis. Root system Which supports the plants and absorbs water and minerals, is usually underground. Plant Tissues Tissues ▪ These groups of cells perform essentially the same function and are commonly of similar structures. Types of Plant Tissues ▪Meristematic tissues ▪Permanent tissues Plant Tissues A. Meristematic tissues CLASSIFICATION ▪ Based on origin ▪ Primary meristems ▪ Secondary meristems ▪ Based on their location within the plant body ▪ Apical meristem ▪ Lateral meristem ▪ Intercalary meristem Plant Tissues MERISTEMATIC TISSUES BASED ON ORIGIN Primary Meristems Secondary Meristems Originates from the Derived from embryo permanent tissues Persists generally throughout the lifetime Examples: of the plant Cork cambium Scar tissues or Callus Examples: Apical meristems Intercalary meristems Cambia Plant Tissues MERISTEMATIC TISSUES BASED ON THEIR LOCATION WITHIN THE PLANT BODY Apical Meristem Lateral Meristem Intercalary (Promeristems) (Cambium) Meristem Found at the tip Found along the It is found at the of the roots and sides of the roots bases of young stems and stems stems and Responsible for Responsible for internodes. the increase in the increase in Responsible for the length of the diameter or the rapid growth roots and the width of the of stems stems. roots and stems. Both in monocot Not present in and dicot plants monocot plants Plant Tissues B. Permanent tissues CLASSIFICATION ▪ They differentiate into three main tissue types: ▪ Dermal tissues ▪ Ground tissue ▪ Vascular tissue Plant Tissues THREE MAIN PERMANENT TISSUE TYPES Dermal Tissue Ground Tissue Vascular Tissue It covers and protects the plant, It carries out different functions It transports water, minerals, and controls gas exchange and based on the cell type and and sugars to different parts of water absorption, in roots. location in the plant. the plant. In stems and leaves, it is covered Specialized conducting tissue by a waxy cuticle that prevents Xylem: transports water and evaporative water loss while the nutrients from the roots to root epidermis is not covered by different parts of the plant, and a waxy cuticle which would also plays a role in structural prevent roots’ absorption of support in the stem. water. Phloem: transports organic compounds from the site of photosynthesis to other parts of the plant. Plant Tissues THREE MAIN PERMANENT TISSUE TYPES Each plant tissue type is comprised of SPECIALIZE CELL TYPES which carry out vastly different functions Dermal Tissue Ground Tissue Vascular Tissue Epidermal cells Parenchyma Tracheid Stomata (guard cells) Collenchyma Vessel elements Trichomes Sclerenchyma Sieve tube cells Companion cells Plant Tissues CELL TYPES IN DERMAL TISSUES Epidermal cells Stomata (guard cells) Trichomes Provide protection Openings that permit gas Hair-like structures on the Absorption of water and exchange for photosynthesis epidermal surface minerals. and respiration. That help to reduce Root hairs increase the surface Guard cells, hence controlling transpiration(the loss of water area of the root, greatly the opening and closing and by above ground plant parts) contributing to the absorption thus regulating the uptake of Increase solar reflectance, and of water and minerals. carbon dioxide and the release store compounds that defend Endodermis which is found only of oxygen and water vapor. the leaves against predation by in the roots and serves as a herbivores. checkpoint for materials entering the root’s vascular system from the environment. Plant Tissues CELL TYPES IN GROUND TISSUES Parenchyma Collenchyma Sclerenchyma Most abundant and versatile Lack secondary cell walls but Have secondary cell walls cell type in plants. have thicker primary cells composed of lignin, a tough They have primary cell walls walls than parenchyma. substance that is the primary which are thin and flexible Long and thin cells that component of wood. Most lack a secondary cell retain the ability to stretch It cannot stretch, and they wall. and elongate; provide important structural Are totipotent: can divide Provide structural support in support in mature stems and differentiate into all cell growing regions of the shoot after growth has ceased. types of the plant system. dead at functional maturity. Responsible for rooting a cut They are highly abundant in stem. elongating stems. The “stringy” bits of celery are primarily collenchyma cells. Plant Tissues CELL TYPES IN GROUND TISSUES Parenchyma Collenchyma Sclerenchyma For photosynthesis in the For shoot support in areas of leaves, and storage in the roots active growth for shoot support in areas TYPES: where growth has ceased. Palisade parenchyma or TYPES: palisade mesophyll has column Fibers shaped, tightly packed cells. long, slender cells, use to make Spongy parenchyma linen and rope. or spongy mesophyll, which are Sclereids smaller-sized, give loosely arranged with air spaces pears their gritty texture, and that allow gaseous exchange are also part of apple cores. between the leaf and the outside atmosphere.  Plant Tissues CELL TYPES IN VASCULAR TISSUES Xylem: transports water and nutrients Phloem: transports organic compounds from the from the roots to different parts of the site of photosynthesis to other parts of the plant plant Tracheids Vessel Elements Sieve Cells Companion Cells Found in all Found only Conduct sugars and other Lie adjacent to types of angiosperms and organic compounds the sieve cells vascular a few other arranged end-to-end with and provide plants specific plants pores metabolic alive at functional support and SIMILARITIES: maturity, but lack a regulation. tubular, elongated cells that conduct nucleus, ribosomes, or water. other cellular structures. arranged end-to-end with perforations They have secondary cell walls hardened with lignin, that provide structural support to the plant. dead at functional maturity Plant Tissues B. Permanent tissues CLASSIFICATION: ▪ Based on origin ▪ Primary permanent tissues ▪ Secondary permanent tissues ▪ Based on the number of cell-type present ▪ Simple permanent tissues ▪ Complex permanent tissues Plant Tissues PERMANENT TISSUES BASED ON ORIGIN PRIMARY PERMANENT TISSUES SECONDARY PERMANENT TISSUES Derived from the apical and intercalary meristems Derived from lateral meristems Plant Tissues PERMANENT TISSUES BASED ON THE NUMBER OF CELL TYPE PRESENT Simple Permanent Complex Tissues Permanent Tissues Composed of only Consists of several one type of cell types of cells Examples: Examples: ▪ Epidermis ▪ Xylem ▪ Parenchyma ▪ Phloem ▪ Collenchyma ▪ Sclerenchyma ▪ Cork Plant Tissues SIMPLE PERMANENT TISSUES Epidermis Parenchyma Collenchyma Sclerenchyma Cork (phellem) An external and An internal tissue An internal tissue An internal tissue An external and protective tissue Consists of living Strengthening Strengthening protective tissue Composed of a cells with and supporting and supporting With cell walls single layer of uniformly thin tissue tissue impregnated thin-walled cells cell walls Composed of Composed of with suberin Some cells are Used for food cells with thick-walled cells modified into manufacturing unevenly guard cells and food storage thickened walls (stomata) Used for food May contain storage cuticle and trichomes Plant Tissues X EPIDERMIS Cuticle Stomata Trichomes Lines the outer waII of the Pores for gas Outgrowth of epidermal ceIIs exchange epidermal Made up of waxy material Present on one cells that protects plants from or both desiccation surfaces of Prevents water loss Ieaves through epidermal cells, it Stomata also prevents the carbon usually close at dioxide required for night. photosynthesis from diffusing from the atmosphere into the leaf or stem. Plant Tissues X SCLERENCHYMA Fibers Sclereids Elongated cells with tapering ends Irregularly shaped cells Elastic, swaying and bending in the Hard surface wind Plant Tissues X COMPLEX PERMANENT TISSUES Xylem Phloem Conducts water and dissolved Conducts food and organic substances substances Plant Tissues X COMPLEX PERMANENT TISSUES Cell Types Xylem Phloem A. CONDUCTING CELLS Vessels: long continuous Sieve tubes : vertically tubes formed by the elongated rows of cylindrical dissolution of the end cells with perforated walls and walls of vertically cytoplasm elongated cells Companion cells: small Tracheids: elongated elongated and nucleated living tapering cells which are cells beside the sieve tubes dead at maturity usually with pitted walls B. STRENGTHENING Xylem fiber: elongated Phloem fibers: thick walls, CELLS pointed cell with very elongated cells thickcell walls Plant Tissues X COMPLEX PERMANENT TISSUES Cell Types Xylem Phloem C. STORAGE CELLS ▪ Xylem parenchyma ▪ Phloem parenchyma D. FUNCTION ▪ Conduction of water and ▪ Conduction of food principally dissolved substances chiefly downward from leaves into stems upward through roots, and roots stems, leaves and flower stalks; also serve as the main strengthening tissue of the plant Plant Tissues X COMPLEX PERMANENT TISSUES Xylem Phloem Made of Dead cells Living cells Cell wall thickness Thick Thin Cell wall materials Lignin Cellulose Permeability Impermeable Permeable Cytoplasm None Cytoplasm lining Transports Water & minerals Food Carried to Leaves Growing parts & storage organs Direction of flow Upwards Up and down Tissue has Fibers Companion cells Roots Roots These cylindrical structures are usually located beneath the soil's surface, through which materials move from the soil to various parts of the plant. Types of Roots Based on Origin 1. Primary root 2. Secondary root 3. Tertiary root 4. Adventitious root Roots TYPES OF ROOTS BASED ON ORIGIN Primary Roots Secondary Roots Tertiary Roots Adventitious Roots The first root formed Roots arising from Roots arising from Roots which arise which is the the primary root. the secondary roots from the plant extension of the whose branches are structures other embryonic root or called rootlets. than roots radicle. Roots Types of Root System ▪ Tap root system ▪ Fibrous or diffuse root system ▪ Some roots are modified to absorb moisture and exchange gases. ▪ Most roots are underground. ▪ Some plants also have adventitious roots, which emerge above the ground from the shoot. TYPES OF ROOT SYSTEM Tap Root System Fibrous or Diffuse Root System Consists of one main stem which arises lateral Consists of several main roots that branch to form roots. a dense mass of intermeshed lateral roots. main root that grows down vertically, and from are located closer to the surface and have a dense which many smaller lateral roots arise. network of roots. It penetrate deep into the soil and are It can help prevent soil erosion. advantageous for plants growing in dry soils are typical of monocots such as grasses. are typical of dicots such as dandelions. Roots Root anatomy ▪ Two regions can be observed: ▪ The root hair zone ▪ The hairless tip ▪ Regions of the root from the tip to the root hair zone ▪ Cross-sectional regions ▪ Groups of tissues that enter to the tissue composition of the old dicot roots. Roots ROOT ANATOMY REGIONS OF THE ROOT FROM THE TIP TO THE ROOT HAIR ZONE Root Cap Region Meristematic or Region of Region of Embryonic Region Elongation or Maturation or Region of Cell Region of Cell Enlargement Differentiation A thimble-shaped Contains the apical Cells increase in Cells have already region that meristem where length which results in attained their final protects the the cells are the growth or structural growing tip of the actively dividing increase in the length characteristics root. and where the of the roots primary meristems are formed: the protoderm, the ground meristem and the procambium. Roots REGIONS OF THE ROOT FROM THE TIP TO THE ROOT HAIR ZONE Region of Maturation or Region of Cell Differentiation Monocots’ subdivision of Dicots’ subdivision of Region of Maturation Region of Maturation Root-hair zone Root-hair zone Zone of primary Zone of primary permanent tissue permanent tissue where all the cells are There are no secondary derives from the apical tissues present because meristem monocots, generally, do Zone of secondary not have cambia where tissues secondary tissues are where tissues derives derived from the cambia either replace or are added to the primary tissue Roots ROOT ANATOMY CROSS SECTIONAL REGIONS Epidermis or Outer Region Cortex or Middle Region Stele or Vascular cylinder or Inner Region usually a single layer of cells the region derived from the ground the region derived from the derived from the protoderm meristem and composed of the procambium and which forms which covers and protects following zones: the central core of the root the inner root Outer zone: a thick layer consisting Regions: of several layers of parenchyma Pericycle Inner zone: consisting of a single Primary xylem layer of thick-walled cells, the Primary phloem endodermis consists of thin-walled Vascular cambium cells with a band-like thickening running around the cells on their radial and transverse walls. This is called the casparian root which contains suberin. Roots Roots CROSS SECTIONAL REGIONS Stele or vascular cylinder or inner region Pericycle Primary xylem Primary phloem Vascular cambium A single layer of A central mass of or Patches of cells Meristematic cells parenchyma which core of xylem between the rays or between the persists as a type of elements with radial arms of the primary xylem and meristematic tissue several radiating primary xylem the primary phloem involved in the arms formation of lateral roots and in some plants, the development of both vascular and cork cambia Roots ROOT ANATOMY GROUPS OF TISSUES THAT ENTER TO THE TISSUE COMPOSITION OF THE OLD DICOT ROOTS Secondary Vascular Tissue Periderm Secondary Xylem: occupies the places formerly Protective tissue that replaces the epidermis occupied by the primary phloem which is pushed after secondary growth is initiated outwardly Phellogen or Cork cambium: cells arising from Secondary phloem: a continuous ring of cells the meristematic activity of the pericycle outer the cambium Phellem or Cork: outer cells produced by the Vascular cambium: meristematic cells between cork cambium the secondary xylem and secondary phloem Phelloderm or Secondary parenchyma: inner cells produced by the cork cambium Once the cork matures, all tissues external to it dies (epidermis and cortex), thus, the covering of an old dicot root is the cork Root adaptation Bulbous roots store starch. Aerial roots and prop roots are two forms of above- ground roots that provide additional support to anchor the plant. Tap roots, such as carrots, turnips, and beets, are adapted for food storage. Epiphytic roots enable a plant to grow on another plant Functions of the Roots Modified or Principal or Economic Specialized Main Function Importance Function Anchorage of the Support Support plant in the soil Food Storage Brace roots Absorption of Photosynthesis Prop roots substances Protection Clinging roots Conduction of Nitrogen fixation Buttresses absorbed Aeration substances Reproduction Functions of the Roots MODIFIED OR SPECIALIZED FUNCTION ▪ Support (Brace roots) ▪ Aerial roots arising from the main stem penetrates the ground Examples: Rubber tree, five-fingers ▪ Support (Prop roots) ▪ Aerial roots arising from the branches which penetrate the ground Examples: Corn, Pandan Functions of the Roots MODIFIED OR SPECIALIZED FUNCTION ▪ Support (Buttresses) ▪ Plant-like extensions from the lower part of the stem Examples: Giant trees ▪ Food storage ▪ Enlarged, fleshy, or succulent roots Examples: Radish, sweet potato, turnips, ube, and beets Functions of the Roots MODIFIED OR SPECIALIZED FUNCTION ▪ Photosynthesis ▪ Green aerial roots Examples: Orchids ▪ Nitrogen fixation ▪ Formation of root nodules containing bacteria in their cells Examples: Soybeans, peanuts, sitaw, bataw, patani Functions of the Roots MODIFIED OR SPECIALIZED FUNCTION ▪ Aeration ▪ With pneumatophores or roots with spongy tissues protruding from the surface of the soil Examples: Mangrove ▪ Reproduction ▪ Development of adventitious buds Examples: Purple yam Functions of the Roots Economic Importance Produces food like carrots, radishes, sweet potatoes, turnips, etc. Aids in digestion and used as laxative(rhubarb); serves as emetic and expectorant (ipecac); while some contain drugs like ginseng. It helps in the production of molasses from sugar beet, which is used in alcoholic beverages Stems Stems Are plant organs which are continuations of the roots usually located above the surface of the soil. The stem with its leaves is called a shoot. All the stems and leaves of a plant constitutes its shoot system. Stems originate from the epicotyl and partly from the hypocotyl of the embryo. Stems FUNCTIONS OF STEM IN PLANTS ▪ It supports buds and leaves and serves as conduits for carrying water, minerals, and food (photosynthates) ▪ It places the leaves in favorable positions for exposure to light ▪ The vascular system inside the stem forms a continuous pathway from the root, through the stem, and finally to the leaves Stems ▪ Generally, it grows above ground, absorbing the light needed for photosynthesis. Related terms ▪ Shoot: a young stem with leaves ▪ Twig: a young stem that is in the dormant winter stage ▪ Branch: A stem that is more than 1 year old, typically, with lateral stems radiating from it. ▪ Trunk: A woody plant’s main stem Stems Classification of Stems ▪ Based on Toughness ▪ Herbaceous stems ▪ Woody stems ▪ Based on Location ▪ Aerial ▪ Underground ▪ Based on Branches ▪ Branched ▪ Unbranced Stems Based on Toughness ▪ Herbaceous stems: ▪ Found in both monocot and dicot plants ▪ Woody stems: ▪ Found only in dicot plants ▪ Some stems are woody only at the base, these are called suffrutescent stems. Stems Based on Toughness Properties Herbaceous Stem Woody Stem Very little or absent and Present, thus are hard 1. Woody tissue thus is generally soft and thick 2. Life span Short-lived Long-lived Very little growth in Increases in diameter 3. Increase in diameter (mainly due to diameter production of wood &cork) 4. Covering Smooth, thin epidermis Rough cork Green Green when young, 5. Color brown when old Present Absent but with 6. Stomata raised areas or lenticels Stems Based on Location (Aerial/epiterranean stems) ▪ Runners or “stolons” ▪ Are fleshy or semiwoody, elongated, horizontal stems that often lie along the soil ▪ Examples: Doob grass, oxalis ▪ Tendrils or “scramblers” ▪ Coil around or thread-like structure which help the plants in climbing ▪ Examples: Grapes, ampalaya, squash Stems Based on Location (Underground/subterranean) ▪ Rhizomes ▪ Underground, horizontal stem which may be swollen due to the presence of stored food ▪ Examples: Ginger, bamboo ▪ Tubers ▪ Short, swollen, terminal portions of an underground stem with the stored food ▪ Examples: Potato ▪ Bulbs ▪ A very small piece of the stem tissue surrounded by numerous fleshly leaves ▪ Examples: Onion, garlic ▪ Corm ▪ Globose, underground stem with papery leaves on its surface ▪ Examples: Gladiolus, Gabi Stems Based on Branching ▪ Unbranched ▪ Stems have a single stem structure ▪ Branched ▪ Stems have divisions and side stems Stem Structure External structures Nodes Internodes Leaf scars Bundle scars Lenticles Buds Internal structures Epidermis Cortex Stele or vascular cylinder External structures of Stem Nodes ▪ Swollen areas where leaves, branches, and buds arise Internodes ▪ Portion between two nodes Leaf Scar ▪ Mark left on the stem by a fallen leaf Bundle Scar ▪ Cut ends of the vascular bundles within each leaf scar Lenticels ▪ Raised pores seen on dicot stems Buds ▪ Undeveloped structures may grow into leaves, shoots, or flowers. External structures of Stem Types of Buds Based on the location or position Based on the presence of the protective coverings Based on the structure which develop from the bud External structures of Stem Based on the Location or Position 1. Terminal or Apical bud - at the end of the stem. 2. Lateral or Axillary Bud - at the upper angle formed by the leaf stalk and the stem called leaf axil. 3. Accessory or Supernumerary bud - beside or above axillary bud 4. Adventitious bud - may develop from roots, a stem internode, the edge of a leaf blade, or callus tissue at the cut end of a stem or root External structures of Stem Based on the Presence of Protective Coverings Protected bud ▪ Covered by a bud scale Naked bud ▪ Not covered by a bud scale External structures of Stem Based on the structures which develop from the bud Vegetative bud or bulbils ▪ It gives rise to leaf and stem Flower buds or floral bud ▪ Gives rise to flower and fruit Internal structures of Stem 1. Like in roots, sections through the apical meristem show three distinct regions of meristematic activity: o The protoderm o The ground meristem o and the procambium 2. From these meristematic tissues will arise the primary tissues of the stem. Internal structures of Stem Epidermis One cell layer derived from the protoderm composed of parenchymatous cells with thick walls and covered by a layer of cuticle (composed of the waxy substance called cutin) Cortex The middle region is composed of an outer zone of collenchyma, an inner zone of parenchyma, and a layer of endodermis consisting of thick-walled cells Stele or Vascular Cylinder It consists of the pericycle, vascular bundle, and pith Internal structures of Stem Young Woody Dicot Stems Young Herbaceous Dicot Stems Old Dicot Stems Herbaceous Monocot Stems Old Woody Stems Internal structures of Stem Young Woody Dicot Stems ▪ Primary vascular tissue is organized in the form of a ring or concentric hollow cylinder. ▪ The primary phloem is generically external to the primary xylem, and a vascular cambium is located between the two. ▪ Entire central portion of the ring constitutes the pith, which is composed of parenchyma Internal structures of Stem Young Herbaceous Dicot Stems ▪ Primary vascular tissue is organized in groups, which are arranged in the form of a broken ring. ▪ Each group is called a vascular bundle or fascicle ▪ The central portion is called the pith, which is made of parenchyma, extending from the pith to the cortex Internal structures of Stem Old Dicot Stems ▪ Group of tissues that enter into the tissue composition of old dicot stems: ▪ Secondary vascular tissues ▪ Periderm Internal structures of Stem Old Dicot Stems Secondary Vascular Tissues Deriving from the vascular cambium, consisting of secondary phloem towards the outside and secondary xylem pushed towards the pith or the center of the stem, obliterating the pith parenchyma to be replaced by the primary xylem forming a solid cylinder of xylem or wood. Internal structures of Stem Old Dicot Stems Periderm Consist of phellem (cork), phellogen (cork cambium) , and phelloderm (secondary parenchyma) Cork cambium originates from the epidermis or a layer of cells in the cortex, which will give rise to the inner phelloderm and outer phellem Internal structures of Stem Herbaceous Monocot Stems Cambium is absent. The greater part of the stem consists of the parenchyma tissue Vascular bundles are surrounded by sclerenchyma and collenchyma cells for support Vascular tissues are scattered bundles of xylem and phloem, numerous at the periphery of the stem Xylem and phloem never form Continuous cylinder tissues: xylem (inner), phloem (outer) Internal structures of Stem Old Woody Stems The cross-section of an old woody stem shows two distinct regions: Bark: all the tissues outside the vascular cambium i.e., secondary phloem, cortex, and the periderm Wood (Xylem) Sapwood (Alburnum): outer part of the wood, which is paler in color Heartwood (Duramen): center part of the wood, which is darker in color Functions of Stem Principal or Main Function Modified or Specialized Functions Economic Importance Functions of Stems PRINCIPAL OR MAIN FUNCTIONS Provides mechanical support for leaves and other plant organs Conduct water, mineral salts and manufactured food Produces new living tissues Functions of Stems MODIFIED OR SPECIALIZED FUNCTIONS Unusual method of support Photosynthesis Absorption of water and mineral salts Uncutinized epidermis Reproduction Storage Protection Functions of Stems Modified or Specialized Functions Modified or Specialized Functions A. Unusual method of support B. Photosynthesis Examples: Examples: ▪ Tendrils: Cadena de amor, ▪ Green stems: Stick plant ampalaya, squash ▪ Phylloclades (dadophylls): Cacti ▪ Twiners: Balloon vine ▪ Root climbers: Creeping Ivy Functions of Stems Modified or Specialized Functions Modified or Specialized Functions C. Absorption of water and mineral D. Uncutinized epidermis salts Examples: ▪ Digman Functions of Stems Modified or Specialized Functions Modified or Specialized Functions E. Reproduction F. Storage ▪ Development of buds in some parts ▪ Fleshy, underground stems of the stem Examples: Ginger, potato, gabi Functions of Stems Economic Importance Sources of lumber, wood pulp for papers, and fibers for linen and rope The bark of the cork oak is used for stoppers, insulation, life preservers, and padding. Quinine, used for the treatment of malaria, is extracted from Cinchona bark Source of rubber Food sources such as the potato tuber Sources of sugar and molasses which come from sugar cane Cinnamon from the bark of cinnamon is used as a food flavoring Tars and wood alcohol are distilled from hardwood trees like oak and hickory Functions of Stems Economic Importance Resin and turpentine are obtained from softwood trees such as yellow pine Cellulose is obtained from plant cell walls of wood, which is used as a base in the manufacture of celluloid, cellophane and rayon, and lacquers (ethyl alcohol) Practical Applications of Knowledge of Stem Structure and Physiology Used in the vegetative propagation of desirable varieties of plants Rooting Grafting Used in horticulture practices Pruning Girdling Practical Applications of Knowledge of Stem Structure and Physiology Used in the vegetative propagation of desirable varieties of plants Rooting: stem cuttings are placed in moist sand or peat mass until adventitious root develop Grafting: freshly cut surfaces of two stems are bound together firmly so that the two cambial layers are at least in partial contact; the basal rooted stem used in a graft is the stock, while the stem piece grafted to the stock is the scion. Practical Applications of Knowledge of Stem Structure and Physiology Purpose of Grafting To propagate a seedless variety of plant To propagate plants whose seeds germinate poorly To ensure more rapid fruiting To check or eliminate parasites which damage the root of the variety from which the scion is taken but to which the array of stock on which the scion was grafted is immune. To acclimate certain plants to the environment in which the stems grow but are unfavorable to the root. Practical Applications of Knowledge of Stem Structure and Physiology Used in the Horticulture Practices Pruning The removal of a diseased, broken, or otherwise undesired branch. Girdling The removal of the complete ring of the bark to shop the downward passage of food that collects above the girdle; the practice is done to produce large fruits, to kill trees in clearing land, and to produce more flowers in the season following girdling. END OF THE LECTURE Reference/s: 1. Guerrero, Jonathan Jaime. General botany with taxonomy : text-workbook.. Educational Pub. (2015) 2. Mauseth, J. D. (2016). Botany. Jones & Bartlett This presentation may not be modified or Publishers. redistributed in whole or in part without permission from Our Lady of Fatima University, College of Pharmacy THIS IS NOT FOR SALE OR DISTRIBUTION