Module 1: Introduction to Pharmaceutical Botany PDF

1 Module 1: INTRODUCTION TO PHARMACEUTICAL BOTANY ⬧ father of plant taxonomy ⬧ swedish botanical taxonomist Lesson 1: Branches of Botany and Early Contributors...

1 Module 1: INTRODUCTION TO PHARMACEUTICAL BOTANY ⬧ father of plant taxonomy ⬧ swedish botanical taxonomist Lesson 1: Branches of Botany and Early Contributors ⬧ the first person to formulate and adhere to a uniform system for defining and naming plants and animal` PLANT ANATOMY ⬧ In 1735 he published Systema Naturae ⬧ In 1753 publication, The Genera of plants and Species study of the internal structure of plants (cells and Plantarum, marked the initial use of the nomenclature for tissues). all flowering plants and ferns – ⬧ In 1758, he applied this system of nomenclature to animals. PLANT MORPHOLOGY PLANT ECOLOGY study of the physical form and external structures of plants study of the interaction of plants with one another and with their environment Philippus Aureolus Theophrastus Bombastus von Hohenheim ERNST HAECKEL ⬧ Father of botany and the real first botanist ⬧ he studied plant morphology, classification and the natural ⬧ german scientist, he coined the word ”ecology” history of plants ETHNOBOTANY Works of Theophrastus: the study of the traditional knowledge and customs of a De Historia Plantarum - (medical use) describes anatomy of people concerning plants and their medicinal, religious, plants and classifies them into structure (trees, shrubs, herbs) and other uses De Causis Plantarum - (economical use) propagation and John W. Harshberger growth of plants that provided guide to farmers and gardeners. ⬧ us botanist, he coined the term “ethnobotany” Robert Hooke Pedanius Dioscorides ⬧ published micrographia in 1665, it was the first important work on microscopy, the study of minute objects through a ⬧ greek physician, pharmacologist and botanist and author of microscope. De Materia Medica — a 5-volume Greek encyclopedia about ⬧ discovered cells in living plant tissue herbal medicine and related medicinal substances; catalog ⬧ used microscope observation to discover plant tissues about medical use of 600 plants ⬧ 3 headings of his book: Aromatic, culinary and medicinal. Marcello Malpighi Shen Nong (500 yrs ago) ⬧ italian doctor, who gave his name to features, like the malpighian tubule system ⬧ Father of Chinese culture ⬧ name means “the divine farmer” ⬧ In 1671, Malpighi’s Anatomy of Plants was published in ⬧ he taught his people how to cultivate grain as food and London by the Royal Society avoding killing animals Nehemiah Grew ⬧ the most well-known work attributed to shen nong is the divine farmers herb-root classic ⬧ Father of Plant Anatomy Huang Di (2679 – 2597 BCE) Grew and Malpighi – founded plant anatomy ⬧ The yellow emperor, founder of Chinese civilization PLANT PHYSIOLOGY ⬧ his classic of internal medicine is important in understanding the basic ideas of traditional chinese herbal study of plant functions science, acupuncture and moxibustion Yin and yang, the Five Phases of Evolutive Change and meridian theory Jan Baptist Van Helmont Louis Lewin (1850 – 1929) ⬧ a Flemish physician and chemist ⬧ the first to demonstrate that plants do not have the same ⬧ german toxicologist first to study psychoactive plants nutritional needs as animals. systematically ⬧ book “phantastica” Joseph Priestly – The Bell Jar Experiment Lewin’s most enduring task was to create a system of classifications 1771, he accidentally discovered that plant releases of psychoactive drugs and plants based on their actions. His original oxygen categories were: put a candle in a glass jar with a plant and in ten days the candle was able to combust. 1. Inebriantia (Inebriants such as alcohol) 2. Exitantia (Stimulants such as Khat or Amphetamine) PLANT TAXONOMY 3. Euphorica (Euphoriants and Narcotics such as Heroin) 4. Hypnotica (Tranquilizers such as Kava) the study that identifies, describes, names, and classifies 5. Phantastica (Hallucinogens or Entheogens such as Peyote plants. or Ayahuasca) PLANT GEOGRAPHY the study of the geographic distribution of plant species and their influence on the earth’s surface Alexander Von Humboldt father of phytogeography he advocated a quantitative approach to phytogeography that has characterized modern plant geography Genetics - study of heredity PLANT SYSTEMATICS Genomics - study of genes and their functions, and related the science of developing methods for grouping techniques organism Gregor Johann Mendel CAROLUS LINNAEUS (1707 – 1778) founder of genetics 2 showed that the inheritance of these traits follows laws TEMPERATE GRASSLAND "PRAIRIE" ADAPTATIONS later named after him ♦ Prairie grasses have narrow leaves - loss less water EVOLUTION ♦ Grasses grow from near their base, not from tip ♦ Grasses are wind pollinated Botany derives components from each of the four big ideas in biology: ♦ Soft stems – bend Big Idea 1: The process of evolution drives the diversity TEMPERATE GRASSLAND "PRAIRIE" ADAPTATIONS Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce, & to maintain dynamic homeostasis. Big Idea 3: Living systems store, retrieve, transmit, and respon to information essential to life processes. Big Idea 4: Biological systems interact, and these system? their interactions possess complex properties. Soft stems enable prairie grasses Many grasses are wind pollinated Charles Darwin to bend in the wind. Narrow leaves and are well-suited to the exposed, minimize water loss. windy conditions of the grassland. ⬧ a british naturalist, proposed the theory of biological evolution by natural selection ⬧ suggested mechanism for evolution : natural selection TROPICAL RAINFOREST ADAPTATIONS Darwin’s concept of natural selection was based on several key ♦ is hot and it rains a lot. ♦ Abundance of water problems: observations: - Harm to plants due to growth of bacteria and fungi. - Risk of flooding. Soil erosion and rapid lost of nutrients from traits are often heritable the soil. more offspring are produced than can survive ♦ the tropical rainforest is very thick, and not much sunlight is able offspring vary in their heritable traits to penetrate to the forest floor. ADAPTATIONS adjustment or changes in behavior, physiology, and structure TROPICAL RAINFOREST ADAPTATIONS of an organism to become more suited to an environment 1. Drip tips and waxy surfaces - water run off plants have different adaptations to help them survive (live and 2. Buttresses and prop and stilt roots grow) in different areas 3. Some plants climb on other plants 4. Flowers on the forest floor are designed to lure animal pollinators due to no wind LESSON 2: BIOMES AND PLANT ADAPTATIONS TROPICAL RAINFOREST ADAPTATIONS BIOMES 1. Smooth bark and smooth or waxy flowers speed the run off of Terrestrial biotic communities considered on a global or at least water on a continental scale 2. Plants have shallow roots - capture nutrients Each biome has a characteristic mix of plants and animals 3. Many bromeliads are epiphytes (plants that live on other plants) adapted to that region’s environment. 4. Epiphytic orchids have aerial roots 5. Epiphyte roots are not parasitic and have no contact with the PLANT ADAPTATIONS: Desert ground. 1. Very dry and often hot TROPICAL RAINFOREST ADAPTATIONS 2. Rain often comes all at the same time. 3. The rest of the year is very dry. 4. Lots of direct sunlight shining on the plants. 5. Soil is often sandy or rocky and unable to hold much water. 6. Winds are often strong and dry out plants. 7. Plants are exposed to extreme temperatures and drought conditions. 8. Plants must cope with extensive water loss. DESERT PLANT ADAPTATIONS Drip-tips on leaves Prop roots help Some plants collect help shed excess support plants in rainwater into a ♦ Some plants, called succulents water. the shallow soil. central reservoir. ♦ Some plants have no leaves or small seasonal leaves that only grow after it rains. ♦ Long root systems spread out wide or go deep into the ground to TEMPERATE RAINFOREST ADAPTATIONS absorb water ♦ Some plants have a short life cycle, germinating in response to ♦ The temperate rain forest features minimal seasonal fluctuation rain, growing, flowering, and dying within one year. of temperature: the winters are mild and the summers cool. ♦ Condensation from coastal fogs also add to the dampness. SOIL EROSION ♦ The soil is poor in nutrients. ♦ A nurse log is a fallen tree which, as it decays, provides ecological Leaching – wash out minerals and organic nutrients from the soil. facilitation to seedlings. PLANT ADAPTATIONS: Temperate Grassland TEMPERATE RAINFOREST ADAPTATIONS 1. called prairie, feature with hot summers and cold winters. 1. Epiphytes such as mosses and ferns grow atop other plants to 2. Rainfall is uncertain and drought is common. reach light. 3. The soil is extremely rich in organic material because the 2. Cool temperatures lead to slow decomposition, but seedlings above-ground portions of grasses die off annually, enriching the grow on "nurse logs" to take advantage of the nutrients from the soil. decomposing fallen logs. 4. The area is well-suited to agriculture, and few original prairies 3. Trees can grow very tall due to amount of precipitation. survive today. TEMPERATE RAINFOREST ADAPTATIONS TEMPERATE GRASSLAND "PRAIRIE" ADAPTATIONS ♦ During a fire - the root portions survive to sprout again - Some prairie trees have thick bark - Prairie shrubs readily resprout after fire ♦ Roots of prairie grasses extend deep into the ground ♦ Extensive root systems - prevent animals from pulling them 3 Epiphytes live on other Trees can grow very tall in In floating plants, chlorophyll is restricted Aquatic plants must be plants to reach the sunlight. this very moist environment. to the upper surface. Note: the green color flexible to withstand the on the top of the leaves and the reddish pressures of moving underside of the of the overturned leaf. water. THE TEMPERATE DECIDUOUS FOREST ♦ temperature varies from hot in the summer to below freezing in Module 2: SIGNIFICANCE OF BOTANY IN PHARMACY the winter. ♦ Rain is plentiful, PHARMACOGNOSY ♦ Made up of layers of plants ♦ The tallest trees make up the forest canopy ♦ Beneath the canopy, the understory derived from Greek pharmakon, ‘remedy’, and gignosco, ♦ Below the understory is a shrub layer. ‘knowledge’. ♦ Carpeting the forest floor is the herb layer made up of wildflowers mosses, and ferns. the science of biogenic or nature-derived pharmaceuticals and poisons. TEMPERATE DECIDUOUS FOREST ADAPTATIONS TYPES OF DRUGS DERIVED FROM PLANTS: 1. Wildflowers grow on forest floor early in the spring before tree Herbal drugs derived from specific parts of a medicinal plant leaf-out and shade the forest floor 2. Many trees are deciduous Leaves 3. Most deciduous trees have thin, broad, lightweight leaves 4. When the weather gets cooler, the broad leaves cause too much Roots water loss and can be weighed down by too much snow Stem/Bark 5. Trees have thick bark to protect against cold winters Flowers THE TAIGA PLANT Seeds ♦ Also known as boreal forests, ♦ the taiga is dominated by conifers and, most of which are Natural products or compounds isolated from nature evergreen ♦ The taiga has cold winters and warm summers. Extracted >> Isolate Nutraceuticals or ‘functional foods’ TAIGA OR BOREAL FORESTS ADAPTATIONS 1. Many trees are evergreen 2. Many trees have needle-like leaves which shape loses less water Herbal remedies or phytomedicines derived from specific parts of a and sheds snow more easily than broad leaves medicinal plant include: 3. Waxy coating on needles prevent evaporation 1. Herb of St John’s Wort (Hypericum perforatum) – depression/ 4. Needles are dark in color allowing more solar heat to be absorbed used in the treatment of mood disorder. 5. Many trees have branches that droop downward to help shed excess snow to keep the branches from breaking 2. Leaves of Ginkgo biloba - used for cognitive deficiencies (often THE TUNDRA in the elderly), including impairment of memory and affective symptom such as anxiety ♦ cold year-round --it has short cool summers and long, severe winters. 3. Flower heads of Chamomile (Chamomilla recutita) - mild ♦ has a permanently frozen sublayer of soil called permafrost. gastrointestinal complaints and as an anti-inflammatory agent ♦ drainage is poor due to the permafrost and because of the cold, evaporation is slow. 4. Leaves and pods of Senna (Cassia spp.) – for constipation ♦ The tundra receives little precipitation, and is usually in the form Natural products or compounds isolated from nature: of snow or ice Opium Poppy (Papaver somniferum) – Morphine used as an TUNDRA ADAPTATIONS analgesic ⬧ Tundra plants are small (usually less than 12 inches tall) and low-growing due to lack of nutrients Purple Foxglove (Digitalis purpurea) - as a source of digoxin ⬧ Plants are dark in color (treatment for cardiac problems) ⬧ Some plants are covered with hair which helps keep them warm. ⬧ Some plants grow in clumps Pacific yew (Taxus brevifolia) - as a source of taxol (treatment ⬧ Some plants have dish-like flowers that follow the sun for cancer) Cinchona tree (Cinchona spp; Cinchona pubescens) - it is used for the primary treatment for malaria. PLANT ADAPTATIONS IN WATER Galanthus and Leucojum species (Galanthamine) used in ⬧ Underwater leaves and stems are flexible cognitive disorders. ⬧ Some plants have air spaces in their stems ⬧ Submerged plants absorb water, nutrients, and dissolved gases Meadowsweet (Filipendula ulmaria)- aspirin (acetylsalicylic through the leaves directly from the water. acid) which has an anti-inflammatory and analgesic property ⬧ Roots and root hairs reduced or absent ⬧ Some plants have leaves that float atop the water Willow (Salix Purpurea) bark - as a source of Salicin and ⬧ In floating plants chlorophyll is restricted to upper surface of derivatives (model for aspirin), use chronic and acute leaves (part that the sunlight will hit) inflammatory conditions ⬧ Some plants produce seeds that can float Periwinkle (Catharanthus roseus) - where vincristine and vinblastine was isolated which is used as antitumor drug PLANT ADAPTATIONS IN WATER Coffee (Coffea arabica) and tea (Camellia sinensis) - as sources of caffeine (stimulant) Nutraceuticals or ‘functional foods’ 4 Many foods are known to have beneficial effects on health. 9. TSAANG GUBAT Examples include: Common Name: Wild Tea garlic, ginger, turmeric and many other herbs and spices Anthocyanin- or flavonoid-containing plants such as Scientific Name: Carmona retusa bilberries, cocoa and red wine Family Name: Boraginaceae Carotenoid- containing plants such as tomatoes, carrots and many other vegetables. Therapeutic Use/s: used as a mouthwash DOH TOP 10 HALAMANG GAMOT 10. SAMBONG Common Name: Ngai Camphor or Blumea Camphor 1. BAWANG Scientific Name: Blumea balsamifera Common Name: Garlic Family Name: Asteraceae Scientific Name: Allium sativum Therapeutic Use/s: used to treat kidney stones or antiurolithiasis Family Name: Amaryllidaceae Module 3: PLANT CELL Therapeutic Use/s: anti-cholesterol CELLS 2. AKAPULKO ⬧ smallest living unit Common Name: Ringworm bush, schrub, and “Acapulco” ⬧ discovery was made in 1665 by Robert Hooke, used a primitive Scientific Name: Cassia alata microscope to examine thin slices of cork found in stoppered wine bottles Family Name: Leguminosae ⬧ Eukaryotic Cell : cells with nuclei (“eu” – well or good, “karyon” – Therapeutic Use/s: anti-fungal nucleus) ⬧ Prokaryotic Cell : cells without nuclei (“pro” – before, “karyon” – 3. BAYABAS nucleus) Common Name: Guava CELL THEORY Scientific Name: Psidium guajava ⬧ all biological organism are composed of cells Family Name: Myrtaceae ⬧ cells are the unit of life ⬧ all life comes from preexisting life Therapeutic Use/s: oral/ skin antiseptic DEVELOPERS OF CELL THEORY: 4. YERBA BUENA Matthias Schleiden ⬧ 1838 Common Name: Peppermint ⬧ stated all plants composed of cells Scientific Name: Mentha arvensis ⬧ observed a smaller body within the nucleus that he called “nucleolus” Family Name: Lamiaceae Theodor Schwann Therapeutic Use/s: analgesic/antipyretic ⬧ 1839 ⬧ stated all animals also composed of cells – thus claimed all living things is composed of cells Rudolf Virchow 5. PANSIT-PANSITAN ⬧ 1858 Common Name: Ulasimang-bato ⬧ all cells come from pre-existing cells Scientific Name: Peperomia pellucida CYTOLOGY Family Name: Piperaceae ⬧ Robert Hooke – Father of Cytology Therapeutic Use/s: treatment of arthritis and gout ⬧ the study of the structure and the function of cells. ⬧ The two primary kinds of cells are: 1. Prokaryotic 6. LAGUNDI 2. Eukaryotic – true nucleus Common Name: 5-leaved chaste tree PLANT CELL Scientific Name: Vitex negundo ⬧ basic building block of plant life and they carry out all the functions necessary for survival. Family Nam: Verbenaceae ⬧ they are eukaryotic cells, which have a true nucleus along with Therapeutic Use/s: for cough and asthma specialized structures called organelles that carry out different functions. 7. AMPALAYA CELL WALL Common Name: Bitter Melon or Bitter Gourd ⬧ outermost part of the plant cell ⬧ it is composed of cellulose (main component) and other Scientific Name: Momordica charantia substance like lignin, suberin and cutin. Family Name: Cucurbitaceae ⬧ Cellulose is a structural carbohydrate and considered a complex sugar because it is used in both protection and structure. Therapeutic Use/s: lowering blood sugar and diabetes ⬧ Contains a sub-organelle called "plasmodesmata" 8. NIYOG-NIYOGAN CYTOPLASM ⬧ “Cell Jello” Common Name: Chinese Honey Suckle ⬧ it is present within the cell membrane of all cell types and Scientific Name: Quisqualis indica contains all organelles and cell parts. ⬧ cytoplasm is responsible for giving a cell its shape and most Family Name: Combretaceae chemical. processes take place here. Therapeutic Use/s: used to eliminate intestinal parasites (antihelminthic) CYTOSKELETON “Framework” 5 ⬧ involved in the movement within the cell. A. Chloroplast (proplastid) Green plastids Functions: maintains cell shape and help in internal movement and B. Leucoplast motility Colorless plastids Some are involved in the storage of starch (amyloplast) MICROTUBULES - made up of protein tubulin If oil (elaioplast) MICROFILAMENTS - made from G-actin protein If air storage of proteins (aleuroplast) Example: Tubers / Roots 7 Stems of plants MICROTUBULES C. Chromoplast ⬧ these are large tubular structures composed of the protein Plastids with red and yellow pigments called Carotenoids tubulin. ⬧ move chromosomes during cell division. (spindle fibers) GOLGI BODIES “dictyosomes” ⬧ part of the structure of cilia & flagella ⬧ composed of circular, flattened vesicles of cisternae aligned in stacks. ⬧ "Packaging of proteins" areas, transport of substances to and MICROBODIES from the cell. ⬧ small, spherical organelles with specialized enzymes & are bound ⬧ named after Camilo Golgi (discoverer, 1898) by single membrane. Peroxisome CELL MEMBRANE / PLASMA MEMBRANE Glyoxisome ⬧ also calles as “plasmalemma” ⬧ selectively permeable which regulates the entrance and exit of Lysosomes substances in a cell. ⬧ its basic function is to protect the cell from its surroundings. LYSOSOME ⬧ it is an organelles that contain digestive enzymes. PLASMODESMA ⬧ only in ANIMAL cells ⬧ holes all over the cell wall which allows the nutrients to enter the cell and also allows the waste to exit the cell. PEROXISOME ⬧ tiny strands of cytoplasm thread that connects and extends between cell openings ⬧ it is a membrane-bound packets of oxidative enzyme ⬧ Chemical communication ⬧ Contain enzymes needed by plants to survive during hot conditions, process is called PHOTORESPIRATION STRUCTURES OF NUCLEUS GLYOXISOME NUCLEUS ⬧ it converts the fatty acids to sugar as fuel for respiration ⬧ structure that stores DNA and acts as a cell's command center. ⬧ eg. seed germination ⬧ it is surrounded by the nuclear envelope and is filled with nucleoplasm. ⬧ the nuclear envelope contains nuclear pore which allow CYTOPLASMIC STRUCTURES molecules with the appropriate nuclear import and export signals in and out of the nucleus. ENDOPLASMIC RETICULUM ⬧ CONTROL CENTER OF THE CELL ⬧ system of membrane-bound channels visible only under the electron microscope NUCLEAR ENVELOPE ⬧ the membrane that surrounds the nucleus ⬧ transport of material within the cell ⬧ a semi-permeable membrane that regulates the passage of ⬧ connected with the outer membrane of the nucleus substance into and out of the nucleus ⬧ modification of proteins ⬧ acts like the “cell membrane” of the nucleus NUCLEUSPASM Smooth Endoplasmic Reticulum ⬧ or Nuclear sap ▪ ribosomes aren’t attached. ⬧ the fluid portion of the nucleus ▪ Lipid + phospholipid are synthesized CHROMATIN ▪ Function: Synthesis, storage, or secretion of lipids ⬧ darkly staining material suspended within the nucleoplasm ⬧ portion of the chromosome visible only when the cell is Rough Endoplasmic Reticulum dividing. ▪ ribosomes are attached. ▪ Synthesis of protein CHROMOSOMES ▪ Function: Synthesis, storage, or secretion of proteins. ⬧ condensed chromatin strands ⬧ contains the "genes" that determines the hereditary characteristics of the cell. RIBOSOMES ⬧ controls the activity of the cell. ⬧ these are dense granules present in the cytoplasm involved in protein synthesis. NUCLEOLUS ⬧ it may be free or attached to the endoplasmic reticulum. ⬧ its primary function is to assemble ribosomes, is the largest structure in the cell nucleus. MITOCHONDRIA ⬧ the nucleolus organizes regions of chromosomes which harbour the genes for pre-rRNA, are the foundation for the ⬧ double layered organelle of the plant cell. nucleolus. CRISTAE - inside folds ⬧ its main function is to perform cellular respiration and to INCLUSION BODIES regulate cellular metabolism. ⬧ responsible for generating energy in the cell by converting VACUOLE - vacuus (empty) glucose and oxygen to ATP. ⬧ filled with aqueous solutions containing various dissolved ⬧ "powerhouse of the cell” substances ⬧ bound by VACUOLAR MEMBRANES (tonoplast) similar function ATP- Adenosine Triphosphate with plasma membrane Functions: PLASTIDS Useful for maintaining cell structure and water balance ⬧ they occur in a variety of shapes and sizes (with the chloroplast) Used for the storage of waste and food ⬧ for higher plants, the chloroplast resemble 2 frisbees glued together. Higher plants have more chloroplast. CELL SAP ⬧ fluid portion of the vacuole ⬧ Grana found within the chloroplast formed from membranes like ⬧ slightly acidic, vacuole also contains sugar, organic acids, and a stack of coins soluble proteins ⬧ Thylakoids stacks of 2-100 found in each granum; it contains green chlorophyll pigments; where the 1st steps of Rhoeo Discolor photosynthesis happen. - bangka-bangkaan Monocot: dumbbell ⬧ Rounded, oval, or irregularly shaped protoplasmic bodies which Dicot: kidney-shaped are three main types: 6 STOMATA - are dotted tiny opening or pore that is used for gas Metaphase -chromosomes are lined up precisely on the metaphase exchange. They are mostly found on the under-surface of plant plate, or middle of the cell. leaves (or sometimes upper) which allows entry of CO2 and the diffusion of 02. Anaphase - spindle pulls sister chromatids apart. Telophase - chromatids begin to decondense and become GUARD CELLS - controls water loss when the guard cells inflate or chromatin. Spindle disappears. deflate, by opening or closing of pores Cytokinesis Chlorophyll - chloroplast: The green color of the upper surface is due - divide cell and organelles. Actin ring, or cleavage furrow splits cell. to the chloroplasts and chlorophyll that is present in the mesophyll cells near the upper epidermis. - the division of the cytoplasm to form two new cells, overlaps with the final stages of mitosis. Anthocyanin- vacuole: The cells of the lower epidermis of Rhoeo discolor contain this pigment that is dissolved in the - cell plate forms down the middle of the cell, splitting it into two cytoplasm. daughter cells separated by a new wall. MEIOSIS Enumerate the Plant Cell Structures: ⬧ type of cell division in sexually reproducing organisms that reduces CELL WALL the number of chromosomes in gametes CYTOPLASM MICROTUBULES THE STAGES OF MEIOSIS I AND II MICROBODIES (LYSOSOMES / PEROXISOME / GLYOXISOME) Enumerate the Cytoplasmic Structures ER RIBOSOMES GOLGI BODIES PLASTIDS CELL MEMBRANE PLASMODESMA Enumerate the Structures of Nucleus NUCLEAR ENVELOPE NUCLEAR SAP CHROMATIN CHROMOSOMES NUCLEOLUS GROWTH AND DIVISION OF THE CELL CELL DIVISION ⬧ Cell division is the process in which one cell, called the parent cell, divides to form two new cells, referred to as daughter cells. Module 4: PLANT HISTOLOGY ⬧ Cell division is simpler in prokaryotes than eukaryotes because prokaryotic cells themselves are simpler. study of tissues (structure) ⬧ Prokaryotic cells have a single circular chromosome, no histos - tissue logia -study of nucleus, and few other organelles. ⬧ Eukaryotic cells, in contrast, have multiple chromosomes PLANT TISSUE contained within a nucleus. a group of closely associated cells that perform related functions and are similar in structure. CELL CYCLE or Tissue – a group of cells performing a common function ⬧ An orderly series of events where cells divide ⬧ 2 divisions: 1. INTERPHASE a period in which chromosomes are NOT visible with light microscope living cells are NOT dividing 3 INTERVALS: I. G1 - (growth or gap one) lengthy period after the nucleus divides; RNA are ribosomes are produced & cell increase in size PLANT TISSUE SYSTEMS: II. S- synthesis - DNA replication takes place functional unit of plant tissues III. G2- (growth or gap two) mitochondria & other organelles Has three types/ tissue system: Dermal, Ground and divide; microtubules are produced; coiling & condensation Vascular of chromosomes begin 2. MITOSIS 2 Types of Plant Tissues: where one cell divides into two and each of the two cells to produce two more daughter cells. 1. Meristematic Tissues Location: MERISTEM (found in roots and stem tips) ▪ site of cell division ▪ Simple Tissues – only one type of cell CYTOKINESIS- normally comes with mitosis; division of the ▪ Complex Tissues – more than one type of cell remainder of the cell 2. Permanent Tissues The daughter cells have the exact number of chromosomes as ▪ Tissues do not undergo cell division the parent cell MITOSIS MERISTEMATIC TISSUE/ MERISTEM Prophase -nuclear envelope breakdown, chromosome regions where cell division produce plant growth condensation, spindle formation. where tissues originate 7 has two types: the epidermis is usually one cell thick, but a few plants produce aerial roots called velamen roots. o SAM - Shoot Apical Meristem: upper part of the plant; produces leaves, stems, and flowers Most epidermal cells secrete a fatty substance called cutin within and on the surface of the outer walls. o RAM – Root Apical Meristem: underground part; produces roots forms a protective layer called the cuticle. Lenticels – gas exchange PERIDERM The periderm constitutes the outer bark and is primarily composed of somewhat rectangular and boxlike cork cells, which are dead at maturity. it secretes a fatty substance, suberin. waterproofing to protect the phloem and other tissues from drying out and mechanical injury. MESOPHYLL 3 Primary Meristem: interior form PROTODERM – outermost and form epidermis location where most of the photosynthesis takes place GROUND MERISTEM - ground tissue (cortex and pith) PALISADE MESOPHYLL- upper region with compactly stacked barrel PROCAMBIUM – innermost – where primary vascular tissues is shaped or post shaped parenchyma cells in two rows; with 80% of found leaf chloroplast SPONGY MESOPHYLL- lower region containing loosely arranged 3 primary kinds of meristems: parenchyma cells with lots of air spaces between them, with cells APICAL MERISTEMS having-numerous chloroplasts. NOT IN MONOCOTS meristematic tissues found at the tip of roots and shoots, which increase in length as it produces new cells. responsible for primary growth. B. GROUND TISSUE (simple tissues) ▪ these tissues are involved in photosynthesis, storage, LATERAL MERISTEMS regeneration, support, and protection. increase width of stems and roots ▪ the three types of ground tissue include parenchyma, collenchyma, and sclerenchyma. responsible for secondary growth 2 types of lateral meristems: The 3 Basic Types Of Plant Tissue: Simple Tissues ▪ vascular cambium – produces vascular/secondary tissues, for PARENCHYMA support and conduction have thin cell walls and large vacuoles and are most abundant of ▪ cork cambium – runs the length of roots and stems of woody all the cells. plants. It lies outside the vascular cambium. intercellular space is found. Main function: to perform photosynthesis and store protein INTERCALARY MERISTEMS and starch. grasses and related plants - neither vascular / cork cambium have apical meristems in the vicinity of nodes (these are leaf COLLENCHYMA attachment areas) composed of elongated cells and have thick cell walls. develops at intervals along stems, where, like the tissues no intercellular space. produced by apical meristems, their tissues add to stem length. Main function: to provide support for growing tissues, like stem. TISSUES PRODUCED BY MERISTEMS ❖ Simple Tissues – composed of one cell type SCHLERENCHYMA ❖ Complex Tissues – composed of two or more cell types dead at maturity composed of narrow dead thick-walled cells, impregnated with lignin. A. DERMAL TISSUE (complex tissues) Main function: to provide support for the plant. ▪ it protects the soft tissues of plants and controls interactions with the plants surroundings. ▪ the epidermis is a dermal tissue that is usually a single layer of C. VASCULAR TISSUE (complex tissues) cells covering the younger parts of a plant. It secretes a waxy ▪ composed of xylem and phloem, which function in the layer called the cuticle that inhibits water loss. transport of water and dissolved substances. ▪ Functions: transports material between the root and the shoot of the plant. LEAF - Internal Anatomy/Structure 3 regions: Epidermis, Mesophyll, Veins EPIDERMIS: A Complex Plant Tissue covers and protects plant surfaces secretes a waxy and waterproof cuticle In plants with secondary growth, periderm (woody plants) replaces epidermis (young plants). 8 Pits- are depressions in cell walls where the secondary walls does not form. Hairs of a different nature occur on the epidermis of aboveground parts of plants. These hairs, also referred to as trichomes, form outgrowths consisting of one to several cells. Leaves also have numerous small pores, the stomata, bordered by pairs of specialized epidermal cells called guard cells. Guard cells differ in shape from other epidermal cells; they also differ in that chloroplasts are present within them. Some epidermal cells may be modified as glands that secrete protective or other substances, or modified as hairs that XYLEM either reduce water loss or repel insects and animals that might a.k.a. conducting sclerenchyma otherwise consume them. conducted water and dissolved minerals conducting cells are dead and hollow at maturity consists of a combination of parenchyma cells, fibers, vessels, tracheids, and ray cells(lateral (sideway) conduction). Vessels are long tubes composed of individual cells, called Module 5: ROOTS vessel elements. Tracheids - are dead at maturity and have relatively thick secondary cell walls, are tapered at each end, the ends overlapping with those of other tracheids. (no openings and are usually pairs of pits present wherever two tracheids are in contact with one another) PHLOEM conducts dissolved food materials (primarily sugars) produced by photosynthesis throughout the plant. main conducting cells are sieve-tube members. companion cells assist in the loading of sugars Vegetative: Non-sexual/non-reproductive parts of plant. Reproductive: Sexual/reproductive parts of plants FUNCTIONS OF ROOTS ❖ Anchorage of the plant in the soil ❖ Absorption of water and minerals ❖ Conduction of water and minerals upward to the stem ❖ Reproduction in the form of plant propagation ❖ Storage of food HOW ROOTS DEVELOP? When a seed germinates, the radicle, a part of the embryo (immature plantlet) within it, grows out and develops the first root. Above the radicle is the embryonic stem called hypocotyl supporting the cotyledon(1st leaf). Radicle emerge from the seed through micropyle (seed scar) while the shoot emerge from the plumule (shoot – above ground part of plant). TWO MAIN TYPES OF ROOT SYSTEMS Тар Root System - primary root Fibrous Root System - web off in many directions Pith – soft central portion and its central portion is surrounded by vascular bundles Endodermis- layer of cell between cortex and vascular tissue in roots (help to regulate water loss) Pericycle – In dicot roots, the pericycle strengthens the roots and provides protection for the vascular bundles. 9 2. Secondary roots - from primary 3. Tertiary roots - grows in various directions INTERNAL ROOT STRUCTURE Four Regions of a Typical Root: 1. Root cap - thimble-shaped 2. Region of Cell division -meristematic region 3. Region/Area of elongation -root lengthening 4. Region/Area of maturation - fully develop i. ROOT CAP 1. Location: tip of the root 2. Tissue: Parenchyma cell that is produced by Calyptrogen 3. Shape >> thimble 4. Functions: TAPROOT SYSTEM Protection from damage of root tip Mucilage – slimy substance- smoothly ⬧ found in dicot plants Gravitropism – helps roots grow towards the sunlight ⬧ the primary root grows longer and thicker than the secondary Amyloplast – “statoliths” that store starch roots Advantage of Taproots: ii. REGION OF CELL DIVISION ⬧ cells are composed of apical meristems Anchors plant deeply, helping to prevent the wind from blowing ⬧ Apical meristem - cells divide once or twice per day. them over ⬧ The transitional meristems arise from the tips of roots and Food storage. shoots. These are subdivided into 3 meristematic areas: Drought tolerance. a. The Protoderm: outermost; forms the epidermis b. The Ground Meristem: forms the ground tissue (cortex and pith) ⬧ The main roots of a plant, generally grows straight down from c. The Procambium: forms the vascular tissues the stem. i. It is often used for human or animal consumption. (carrot, yam, radish, turnips, & sweet potato) iii. REGION OF ELONGATION ii. Taproot swollen: a single, large taproot extending from stem. ⬧ cells become several times longer and wider iii. Taproot primary. Larger than average root going deeper into the ⬧ tissues have no specific functions yet soil. iv. Taproot even: a number of large, equal-sized taproots. iv. REGION OF MATURATION OR DIFFERENTIATION COMPARISON OF TAPROOT SYSTEMS ⬧ specialized function ⬧ inside of the root >> xylem /phloem ⬧ outside the root >> epidermis ROOT HAIR - increase absorptivity capacity ⬧ It is a tubular outgrowth of a hair-forming cell on the epidermis of a plant root. ⬧ Cuticle exists on root but not on root hairs. ⬧ FUNCTION: Increase the surface area for the absorption of water and minerals nutrients. Epidermis - outer layer FIBROUS ROOT SYSTEM Cortex - lying between the epidermis and inner tissues ⬧ found in monocot plants Endodermis – area between the cortext and vascular bundlers → lignin & ⬧ the secondary roots continue to grow & eventually all the roots suberin are of equal or nearly equal size ⬧ hair-like Casparian Strip: Wax (suberin) around endodermis ▪ Function: It regulates water and mineral uptake and Advantages of Fibrous Root: transport by the roots Absorbs water and nutrients quickly Vascular Cylinder Helps prevent soil erosion as they anchor plants to the top layers also called as "stele" of soil. Ex. Grass contains xylem, phloem, and pericycle. COMPARISON OF TAPROOT SYSTEMS Pericycle: outer layer of vascular cylinder; composed of parenchyma cells that divide to produce lateral roots (secondary roots). Can be found inside the endodermis Shape: o Monocot: Circular-shaped; with pith in the center o Dicot: X-shaped SECONDARY GROWTH IN DICOT ROOTS Many roots have secondary growth when lateral meristems are produced. ROOT STRUCTURE 1. In woody dicots and conifers, parts of the pericycle and the ⬧ root growth begins with seed germination. parenchyma cells around the primary xylem and phloem become a ⬧ primary root growth is controlled by apical meristem ⬧ secondary growth is controlled by lateral meristem vascular cambium EXTERNAL STRUCTURE OF A ROOT 2. The cells of the root vascular cambium divide to produce secondary phloem to the outside of the root and secondary xylem to the inside. 1. Primary root - 1st root 10 3. The patches of new secondary vascular tissue merge together with the The contractile roots continually pull the plants deeper into the primary vascular tissue, forming a circular ring of vascular tissue. soil as the stem elongates. The pericycle also gives rise to a cork cambium in the roots. The cork Example: Lily (Lilium spp.), Dandelion (Taraxacum officinale), and hyacinth cambium produces cork which becomes part of the bark of the root. (Hyacinthus orientalis) DICOT ROOT VS. MONOCOT ROOT BUTTRESS ROOTS Parts Dicot Root Monocot Root Large roots on all sides of a tall or shallowly rooted tree. It gives rise to lateral roots, The pericycle present Provide support and stability to a tree. cork cambium, only only produces the Pericycle and the part of the lateral roots Example: Fig tree and other tropical trees lateral roots vascular cambium PARASITIC ROOTS Xylem & Limited in numbers Numerous in numbers Phloem They parasitize their host plants via peg-like projections called Pith Absent Pith is large and well haustoria, which develop along the stem in contact with the developed host. Saprophyte – organisms that lack chlorophyll and obtain The secondary growth occurs in the dicot root while it is absent in nutrients from organic matter. monocot root. AERIAL ROOTS Orchids produce velamen roots, corn plants have prop roots, ivies have adventitious roots and vanilla orchids have photosynthetic roots. They can facilitate climbing and support to the plant. SYMBIOTIC ROOTS Mycorrhizae form a mutualistic association with plant roots. Mutualism between a plant and bacterium which allows for the fixation of atmospheric nitrogen (photosynthesis purposes). SPECIALIZED ROOTS Root + fungi = mychorrhiza (better absorption of phosphorus from the soil) FOOD - STORAGE ROOTS 2 types of Mycorrhizas: ▪ Ectomycorrhizae - fungi grow in the outermost layers of the Roots are enlarged and store large quantities of starch and cortex cells of the root (trees) other carbohydrates, which may later be used for extensive ▪ Endomycorrhiza - fungi penetrates the cortex cells, all the way growth. to the endodermis (woody and herbaceous plants) Example: sweet potatoes (Ipomoea batatas), yams (Dioscorea alata), and Root + bacteria (another exp of mycorrhizas) = rhizobia (nitrogen fixation, cassava (Manihot esculenta) convert N2 to NH3 to use by plant for protein synthesis) ▪ The bacterium is rewarded with food and a place to live. WATER - STORAGE ROOTS Plants that grow in arid regions are known for growing structures MECHANISM OF WATER AND NUTRIENT ABSORPTION used to retain water & used these water supply when the supply ⬧ The absorption of water and dissolved minerals occurs through in the soil is inadequate. the epidermis Example: pumpkin (Cucurbita maxima), manroots (Marah oreganus), ⬧ The absorption of water is chiefly via osmosis, which occurs because: calabazilla (Cucurbita perennis), and watermelon (Citrullus lanatus) 1. Water is present in higher concentrations in the soil than within the PROPAGATIVE ROOTS epidermal cells Produces adventitious buds (buds appearing in places other 2. Epidermal cells is permeable to water than stem) along the roots that grow near the surface of the ground. The buds develop into aerial stems (suckers). The rooted Water Absorption in Plants suckers can be separated from the original root & grow individually. Example: Cherries (Prunus avium), Apple (Malus domestica), and Pear (Pyrus communis) Rice-paper plants – Tetrapanax papyrifera Tree-of-heaven – Ailanthus altissima Horseradish- Rorippa armoracia Canada Thistle - Cirsium arvense PNEUMATOPHORES Breathing roots to help plants that grow in very wet areas like PHARMACEUTICAL AND PHARMACOLOGICAL IMPORTANCE OF swamps to get enough oxygen. These roots act like snorkel ROOTS tubes for plants, rising up above the surface of the water so that the plant can get oxygen. Herbal Drugs obtained from roots and underground parts: Example: black mangrove (Avicennia germinans) and yellow water weed (Ludwigia repens) GABI Colocasia esculenta CONTRACTILE ROOTS Tubers yield amino acids. Tubers are digestive, laxative, diuretic, lactagogue (increase lactation), and styptic (stop bleeding). 11 SUPPORT MAKAHIYA offer physical support for the leaves Mimosa pudica CONDUCTION Roots yield flavonoids, phytosterol, alkaloids, amino acids, tannins, glycoside, fatty acids. stems contain vascular tissue Roots are bitter, astringent, acrid, alexipharmic, antispasmodic, GROWTH aphrodisiac, constipating, cooling, diuretic, emetic, febrifuge (reduce fever), resolvent, vulnerary (remedy). cell division and elongation STORAGE ANIS (LICORICE) modified to store food and (or) water. STEM AS FOOD - asparagus, broccoli, potato, cauliflower Glycyrrhiza glabra Roots yield starches (30%), pectins, simple sugars, gums, mucilage (rhizome), polysaccharides, amino acids, triterpene STEM TERMINOLOGY saponin, flavonoids. Sweet root is said to contain a glycyrrhizin, a saponin glycoside, 1. SHOOT – a young stem (1 year old or less) with leaves that is roughly 50 times sweeter than cane sugar. Demulcent, emollient, expectorant, anti-inflammatory, 2. TWIG – a young stem (1 year old or less) that is in the dormant antispasmodic, alterative, diuretic and laxative. winter stage (no leaves) 3. BRANCH – a stem that is more that 1 year old typically with BIGA lateral stems radiating from it Alocasia macrorrhizos 4. TRUNK – a woody plant’s main stem Rhizomes contain phytosterols, alkaloids, glucose and fructose. Rootstock considered laxative, diuretic. TYPES OF STEM BAYABANG HERBACEOUS STEMS - thin, soft, and green in color except those that Nephrolepis cordifolia grow underground. Tubers were found to contain high amounts of moisture, fat, carbohydrate, and calcium; protein was maximum in the rhizome WOODY STEMS - taller, thicker, and harder than herbaceous part. EXTERNAL PARTS OF STEM BEGONIA 1. BUD - stem's primary growing point. Begonia coccinea Roots of the juice used for conjunctivitis. 2. TERMINAL BUD - single bud found at the apex of the stem Tuberous roots and fruits are anodyne, antiphlogistic and antispasmodic. 3. BUD SCALES - protect lateral and terminal bud SPIDER PLANT 4. TERMINAL BUD SCALE SCARS - marks left on the stem from the previous years which serve as external measure of annual Chlorophytum comosum growth Root tubers have yielded sapogenins and saponins. 5. LATERAL BUDS/AXILLARY BUDS - buds that occur in the leaf Studies have suggest antitumor axils on the side of a stem. antiproliferative, indoor air-purifying, phytoremediative, burn wound healing properties. 6. LEAF SCAR - mark that leaves on the stem after the leaf falls KOGON 7. PETIOLE - stalk that extends from the stem to the base of the leaf Imperata cylindrical Considered antifebrile, anthelmintic, antibacterial, diuretic, 8. LENTICEL - pores that allow for gas exchange febrifuge, restorative, styptic, tonic 9. NODE - segment of stem where leaves and lateral buds are attached. (Above or below ground) TALAHIB 10. INTERNODE - section of a stem between two nodes. Saccharum spontaneum Various root extracts yielded terpenoids, steroids, glycosides, 11. BUNDLE SCAR -used in the identification of the woody plants tannins, flavonoids, carbohydrates roots are considered sweet, and it is a mark left in the leaf scar from the vascular tissue astringent, emollient, refrigerant, diuretic, lithotriptic, purgative, attachment. tonic, aphrodisiac. Bundle scar - tiny bumps in leaf scar where vascular tissue enter the leaf from the stem. Module 6: stems bundle scars because they mark the places where bundles of vascular STEM tissue were located. ⬧ the stem is the aerial part of the plant. ⬧ mechanical support ⬧ it is the site where leaves and reproductive shoots get attached. ⬧ a stem exposes the leaves for photosynthesis and positions the reproductive shoots for optimal access to pollinators and dispersal agents. ⬧ it also conducts water and minerals from roots to the leaves and solutes from leaves to storage and use sites. STEM FUNCTIONS Stems have the following 4 functions or jobs: 12 TWO TYPES OF GROWTH IN STEMS Primary growth increases length of the stem Herbaceous plants mostly undergo primary growth Secondary growth increases thickness of the stem Secondary growth builds woody stem ORIGIN AND DEVELOPMENT OF STEMS HERBACEOUS DICOT AND MONOCOT STEMS Primary Growth - Shoot Apical Meristem (SAM) The apical meristem is located in a bud called a terminal bud, at the Dicot Stem Monocot Stem tip of the stem. Epidermis ⬧ Protoderm to Epidermis A. Trichomes Present Absent B. Cuticle Present Present ⬧ Procambium to Primary Xylem and Primary Phloem Hypodermis Made up of the Made up of the ⬧ Ground Meristem to Pith and Cortex collenchyma sclerenchyma ⬧ Primordium – developing leaves that can be seen in the apex Vascular Bundle Arranged in the Scattered across (terminal bud) of the stem Arrangement form of one or the stem two broken rings Bundle Sheath Absent Present Secondary Growth - Lateral Meristems Cortex & Pith Present Absent Lateral meristems are located in axillary buds Vascular cambium to Secondary Xylem and Secondary Phloem (same WOODY DICOT STEMS function as your primary xylem and phloem) Cork cambium (Phellogen) ⬧ In the early stages of development, the primary tissues of stems of young herbaceous dicots, woody dicots, and cone-bearing trees are all ⬧ Produces Phelloderm (inside) and Phellem (outside) arranged in a similar fashion. ⬧ Cork cells are impregnated with suberin >> protection ⬧ In woody plants, however, obvious differences begin to appear as soon as the vascular cambium and the cork cambium develop. ⬧ Cork cells - Epidermis to Periderm > outer bark ⬧ The most conspicuous differences involve the secondary xylem, or ⬧ Lenticels develop beneath the stomata wood. ⬧ In trees of temperate climates, virtually all growth takes place during the spring and summer and then ceases until the following spring. Woody Dicot Stems Vascular cambium active during the spring produces a xylem called Remember! Annual plants don't do secondary growth, while SPRING WOOD Perennial plants do secondary growth. SUMMER WOOD - xylem with smaller or fewer vessel elements & Annual plants, which complete their entire life cycle from germination large number of the spring to produced after to death within one year. Perennial plants, which live multiple years ANNUAL RINGS - indicates the age of the tree; but it also denotes the climate. TISSUE PATTERNS IN STEMS One year growth of xylem is called an annual ring. STELES – Vascular Cylinder VASCULAR RAYS - lighter streaks seen on transverse or cross section composed of primary xylem, primary phloem, and the pith of tree trunk PROTOSTELE consist of parenchyma cells that may be alive >10 years the simplest form of stele Functions by lateral conduction of nutrients & water from the stele consists of a solid core of conducting tissues in which the phloem (thru xylem & phloem) to the cortex usually surrounds the xylem. Woody Dicot Stems SIPHONOSTELES ⬧ As a tree ages: which are tubular with pith in the center, common in ferns. The protoplasts (cell w/o cell wall) of some of the parenchyma cells that surround the vessels and tracheids grow through the pits in EUSTELES the walls. As the protoplasm continues to expand, much of the cavity of the most present-day flowering plants and conifers have this vessel or tracheid becomes filled. the primary xylem and primary phloem are in discrete vascular ⬧ TYLOSIS (tyloses) - protrusions filled with resins, gums or tannins; bundles that prevent conduction of water & dissolved substance. Results to accumulation of resins, gums and tannins as well as Remember! Vascular cambium and cork cambium both develop from pigments that darken the color of the wood. primary tissue in the stem as a stem enters into secondary growth. Woody Dicot Stems SUMMARY OF PRIMARY AND SECONDARY GROWTH IN A WOODY HEARTWOOD older darker wood at the center. No longer conducts STEM materials. It helps strengthen the tree. not of much use to the tree A tree may live and function perfectly well after the heartwood has rotted away and left the interior hollow. SAPWOOD - lighter; still functioning. xylem closest to the cambium. 13 ⬧ Photosynthesis ⬧ Store water ⬧ prickly pear cactus PHYLLOCLADES (filokleyd) are flattened stems that resemble leaves that can continue growing indeterminately (scale-Iike leaves) SOFTWOOD- no fibers or vessel elements; only tracheids. softer and TUBERS pines and cone-bearing trees swollen, fleshy, underground stem HARDWOOD - wood of woody dicots tuber body is comprised of many parenchyma cells that contain amyloplasts with starch. Store food BULBS underground, consist of basal plate, growing points, flower primordia, and fleshy scales BARK - all tissues outside the vascular cambium, including the found in monocots phloem Two different kinds: 1. INNER BARK - consist of primary and secondary phloem ⬧ Tunicate bulbs have a papery outer covering. Example: onion, tulips, daffodils. 2. OUTER BARK (periderm)- consist of cork tissue and cork cambium protection from digging and drying out. ⬧ Nontunicate / Scaly bulbs lack a papery outer covering. Example: Lily LACTICIFIERS bulbs. susceptible to damage and drying ⬧ Specialized cells or ducts ⬧ Form extensive branched networks of latex-secreting cells ⬧ Found in woody flowering plants BULBLETS ⬧ Most common in the phloem but present throughout all parts of plant a small or secondary bulb that forms in the angle between a leaf and LATEX stem or in place of flowers on certain plants ⬧ a thick fluid that is white, yellow, orange, or red in color and consists THORNS of gums, proteins, sugars, oils, salts, alkaloidal drugs, enzymes, and other substances. are sharp-pointed modified stems ⬧ Function: aids in closing wounds ⬧ Opium poppy – morphine Example: honey locust RHIZOMES SPINES an underground stem. are sharp-pointed modified leaf or stipule (twigs). usually grows horizontally. it helps reduce water loss. capable of producing new shoots and roots. for example, at the base of the petiole of most leaves of the black