Botany PDF

LESSON 1: INTRODUCTION OF BOTANY APPLIED PLANT BIOLOGY  Agronomy – deals with field crops and soils WHAT IS BOTANY?  Horticulture – deals with ornamental plants  Or Plant Biolo...

LESSON 1: INTRODUCTION OF BOTANY APPLIED PLANT BIOLOGY  Agronomy – deals with field crops and soils WHAT IS BOTANY?  Horticulture – deals with ornamental plants  Or Plant Biology and fruit and vegetable crops  Branch of Biology  Forestry – deals with forest conservation and  Scientific study of plants forest products such as lumber  Encompasses growth, structure, physiology,  Economic Botany – deals with plants with reproduction, pathology as well as their commercial importance. economic use and cultivation by humans. CHARACTERISTICS OF PLANT Historical Development of Botany  Plants are highly organized. Like all living things, plants have a complex organization.  Botany involve much more than just Cell - the basic unit of structure and understanding how plants harness energy from function of all living things the Sun. Tissue - group of cells of the same kind;  Humans have been studying plants for as long organ is a structure composed of one or as there have been humans. more types of tissues which work together  Historical studies and developments regarding to perform a specific function organ plants have their roots in agriculture and system, a group of organs that work herbalism when our ancestors learned which together to perform a certain function. plants were useful for nutritional and Organism - an individual living thing that medicinal purposes. may be made up of one or more organ  It was only much later that the field grew to systems. become what we know of as botany, Population - organisms of the same sometimes also referred to as Phytology, when species that live in the same area. people became more interested in Plant Community - comprises all of the Taxonomy, or the description of plant species populations that live in the same area. and their classification into different groups of Ecosystem consists of all living things relatedness. (biotic factors) in a given area, together with the non-living environment (abiotic SUB-DISCIPLINE OF BOTANY factors). Biome - a group of similar ecosystems with  Plant Molecular Biology – study of the the same general type of physical structures and functions of important biological environment. molecules such as proteins and nucleic acids Biosphere - the part of Earth where all live  Plant Biochemistry – study of the chemical exists, including all the land, water and air interactions within plants, including the variety where living things can be found. of chemicals that plants produce.  Plants take in and use energy. All organisms  Plant Cell Biology – encompasses structuresm require energy for their activities, their functions, and life processes of plant cells metabolic activities, which include growth,  Plant Anatomy – study of microscopic plant repair, reproduction, and maintenance. The two structures most important energy related activities in the  Plant Morphology – refers to the structures of living world are photosynthesis and cellular plant parts such as leaves, roots, and stems, respiration. including their evolution and development  Plants respond to stimuli. Plants and other  Plant Physiology – study such processes as organisms respond to stimuli, changes in their photosynthesis and mineral nutrition to environment. Stimuli to which plants respond understand how plants function. include change in the direction, color, or  Plant Genetics – specialized on plant heredity luminosity or light; in temperature or in the and variation orientation toward gravity; and in the chemical  Plant Ecology – study of the interrelationships composition of the surrounding soil, air or among plants and between plants and their water. environment  Plants grow and develop. Growth is an increase  Plant systematics - encompasses the in the size and mass of an organism. In plants, evolutionary relationships among different plant growth results from both an increase in the groups number of cells and an increase in the size of  Plant Taxonomy – a sub-discipline of cells. Growth is part of development, which systematics, deals with the description, naming includes all the changes in a plant or other and classification of plants organism from the start of its life through its  Paleobotany – study of the biology and the immature stage, through its mature stage, to it evolution of plants in the geologic past. death or senescence.  Plants reproduce. Reproduction, the formation  Provide a source of energy. Healthy plants also of a new individual by sexual or asexual means, provide humans with a source of energy and is the most distinctive characteristic of life. food. Plants play an essential part in our Reproduction enables an organism to environment and our diet. They provide us with perpetuate its traits beyond an individual’s own the nutrients, vitamins, minerals, and fiber we death, need to survive. We also need plants to feed  Plant DNA transmits information from one farm animals, which we utilize as source of meat generation to the next. The characteristics of an and dairy products. Planting trees near buildings organism are encoded in its genes, which are decrease the sun’s effect on the outer walls and the units of hereditary information. Genes are roof temperature, which means that heating composed of DNA, the organism molecule that and cooling your home will require less energy, stores and carries important genetic reduce the environmental impact, and save your information in cells. Information encoded in money in the long run. genes that is, in the DNA that composes genes is  Reduce the effects of climate change. One of transmitted from one generation to another. the most significant natural issues today is climate change and the burning of fossil fuels. Importance of Plants Burning fossils results in high levels of carbon  Clean air. Majority of the oxygen we breathe dioxide in the atmosphere and the air we comes from plants. This is because plants use breathe. But, this is when plants come into play. sunlight, water and carbon dioxide to convert On earth terrestrial and oceanic plants store energy into a form that other living things can carbon dioxide from the air to decrease the use, oxygen and power in the form of sugar. number of polluted gases in the environment. One of the biggest threats to the Earth is the Biological Diversity high amount of carbon within the atmosphere Taxonomy – is a methodology that involves from fossil fuels and manufacturing. But systematically classifying elements in a defined through photosynthesis, plants help reduce the hierarchical form. amount of carbon in the atmosphere by storing - used to classify organisms and using it. That means, plants are natural air - tells us how to sort organisms into taxa and purifiers. The more prominent and leafier the taxa into more inclusive taxa. plant is, the better it absorbs carbon dioxide and Six-Kingdom Classification produces more oxygen.  Regulate water resources. The water cycle Archaea – no cell nucleus or any other membrane- keeps water moving above and below the bound organelles within their cells, most but not all surface of the Earth, and plants help regulate have a cell wall. Reproduce asexually by binary or the rainwater runoff. Plants and trees absorb multiple fission, fragmentation or budding; meiosis water after a heavy rain, saving cities money does not occur. from maintaining and pumping out of excessive runoff. Increased vegetation leverage the Eubacteria – prokaryotic, unicellular organisms; capabilities of soil to infiltrate, redistribute reproduce asexually by binary fission rainwater volume, with the potential to fulfill additional environmental, social, and economic Protista – unicellular organisms, reproduce benefits. In addition, vegetation returns water asexually by binary fission and sexually by into the atmosphere through the soil. As a conjugation when two individuals join and exchange result, around 10% of water in the form of genetic material in the nucleus water vapor goes back into the atmosphere, regulating and replenishing the Earth’s stock of Fungi – multicellular with a cell wall, organelles water for the next rainfall and keeping energy including a nucleus, but no chloroplasts; they have running naturally. no mechanisms for locomotion. Nutrients are  Cultivate biodiversity. Creating a secure place acquired by absorption, for the most part, from for animals to live is crucial to sustaining decaying materials. Reproduce via sexual and asexual biodiversity. Unfortunately, urbanization has reproduction. impacted our ecosystem by disturbing animal populations. The most effective way not to Plantae – Multicellular form with specialized disturb animal populations is by giving wildlife a eukaryotic cells, do not have their own means of natural refuge. Creating green spaces even locomotion. Autotrophic, reproduce sexually which around cities is an effective way to wildlife to involves the male pollen grains traveling to the succeed despite living in disturbed territory. stigma of a flower and asexually by the production of Parks and other green habitats illuminate a new plant without the use of flowers. potential synergies among food production and conservation of biodiversity. Animalia – multicellular form with specialized eukaryotic cells; have their own means of locomotion; Heterotrophic; reproduce asexually and sexually by fertilization. Binomial System of Nomenclature  Carolus Linnaeus  Two-part name (genus name and specific epithet)  The first word designates the genus to which the organism is assigned, and the second word is a specific epithet, that is a descriptive word that characterizes the organism.  Genus is capitalized; specific epithet is usually non capitalized; both names are italicized.  Example, the white oak (Quercus alba, sometimes abbreviated Q. alba) and the red oak (Quercus rubra) belong to the same genus, Cell wall - It is a rigid layer which is composed of Quercus polysaccharides cellulose, pectin and hemicellulose. It is located outside the cell membrane. It also LESSON 2: PLANT CELL AND TISSUES comprises glycoproteins and polymers such as lignin, cutin, or suberin. The primary function of the cell The Cell Theory wall is to protect and provide structural support to The development and refinement of magnifying the cell. The plant cell wall is also involved in lenses and light microscopes made the observation protecting the cell against mechanical stress and and description of microscopic organisms and living providing form and structure to the cell. It also filters cells possible the molecules passing in and out of it. The formation of the cell wall is guided by microtubules. It consists  The cell is the basic unit of life of three layers, namely, primary, secondary and the  All living things are made of cells middle lamella. The primary cell wall is formed by  Cells come from pre-existing cells cellulose laid down by enzymes. Botanist Matthaist Schleiden and zoologist Theodor Cell Membrane - It is the semi-permeable Schwann were studying tissues and proposed the membrane that is present within the cell wall. It is unified cell theory that states that all living things are composed of a thin layer of protein and fat. The cell composed of one or more cells; the cell is the basic membrane plays an important role in regulating the unit of life and with Rudolf Virchow, with his studies, entry and exit of specific substances within the cell. concluded that all cells come from preexisting cells For instance, cell membrane keeps toxins from entering inside, while nutrients and essential minerals are transported across. Nucleus - The nucleus is a membrane-bound structure that is present only in eukaryotic cells. The vital function of a nucleus is to store DNA or hereditary information required for cell division, metabolism and growth. Nucleolus: It manufactures cells’ protein- producing structures and ribosomes. Nucleopore: Nuclear membrane is perforated with holes called nucleopore that allow proteins and nucleic acids to pass Plant cells have cell walls, chloroplasts, through. plasmodesmata and plastids, and a large central Plastids - They are membrane-bound organelles that vacuole, whereas animals cells do not. have their own DNA. They are necessary to store starch and to carry out the process of Animal cell is small and irregular or round in shape. photosynthesis. It is also used in the synthesis of cell wall is absent. the nucleus lies in the center. many molecules, which form the building blocks of mitochondria are present in large numbers. plastids the cell. Some of the vital types of plastids and their like the chloroplasts are absent. centrosomes are functions are stated below: present. many small vacuoles are present. Leucoplasts - They are found in the non- photosynthetic tissue of plants. They are used for the storage of protein, lipid and starch. Chloroplasts - It is an elongated organelle enclosed by phospholipid membrane. The chloroplast is shaped like a disc and the stroma is the fluid within the chloroplast that comprises a circular DNA. Each chloroplast contains a green coloured pigment called chlorophyll required for the process of photosynthesis. The chlorophyll absorbs light energy from the sun and uses it to transform carbon dioxide and water into glucose. Chromoplasts - They are heterogeneous, coloured Collenchyma Cells plastid which is responsible for pigment synthesis and They are hard or rigid cells, which play a primary role for storage in photosynthetic eukaryotic organisms. in providing support to the plants when there is Chromoplasts have red, orange and yellow coloured restraining growth in a plant due to lack of pigments which provide colour to all ripe fruits and hardening agent in primary walls flowers.  back-up system of plants Central Vacuole - It occupies around 30% of the  can perform some photosynthesis cell’s volume in a mature plant cell. Tonoplast is a  offer nutrient storage membrane that surrounds the central vacuole. The  provide flexible structure vital function of the central vacuole apart from  can keep leaves from tearing storage is to sustain turgor pressure against the cell  can allow petioles to bend in the wind wall. The central vacuole consists of cell sap. It is a  can give the plant some room to stretch without mixture of salts, enzymes and other substances. breaking Ribosomes - They are the smallest membrane-bound Sclerenchyma Cells organelles which comprise RNA and protein. They These cells are more rigid compared to collenchyma are the sites for protein synthesis, hence, also cells and this is because of the presence of a referred to as the protein factories of the cell. hardening agent. These cells are usually found in all plant roots and mainly involved in providing support Mitochondria - They are the double-membraned to the plants. organelles found in the cytoplasm of all eukaryotic cells. They provide energy by breaking down  dead and found in parts of the plant that are no carbohydrate and sugar molecules, hence they are longer growing also referred to as the “Powerhouse of the cell.”  provide the most support for the plant by creating woody tissue in stems and trunks Lysosome - Lysosomes are called suicidal bags as  contain lots of cellulose and lignin which are they hold digestive enzymes in an enclosed both complex biopolymers that are difficult to membrane. They perform the function of cellular break down, so they last a long time. waste disposal by digesting worn-out organelles,  sclerenchyma fibers are stretched lengthwise in food particles and foreign bodies in the cell. In plants, a plant stem and provide most of a plant’s the role of lysosomes is undertaken by the vacuoles. support  ex. sclereids cells that make up the shells of Plant Cell Types nuts, the hard coatings of seeds like those found Cells of a matured and higher plant become in peaches, plums, and other parts of plants. specialised to perform certain vital functions that are essential for their survival. Few plant cells are Xylem Cells involved in the transportation of nutrients and water, Xylem cells are the transport cells in vascular plants. while others for storing food. They help in the transport of water and minerals from the roots to the leaves and other parts of the The specialised plant cells include parenchyma cells, plants. transports and stores water and water- sclerenchyma cells, collenchyma cells, xylem cells and soluble nutrients in vascular plants phloem cells. Following are some of the different types of plant Phloem Cells cells: Phloem cells are other transport cells in vascular plants. They transport food prepared by the leaves Parenchyma Cells to different parts of the plants. Responsible for Parenchyma cells play a significant role in all plants. transporting sugars, proteins, and other organic They are the living cells of plants, which are involved molecules in plants in the production of leaves. They are also involved in the exchange of gases, production of food, storage Meristematic cells of organic products and cell metabolism. These cells  cells plants use to grow are typically more flexible than others because they  undifferentiated cells are thinner.  can be found in the tips of roots and shoots  do most of the work for the plants (apical meristems)  general-use cell  can be found in the lateral or side position  perform most of the photosynthesis within the vascular systems (lateral meristems)  offer energy and nutrient storage  can be found in the intercalary position where  perform nutrient transport branches intersect and where leaves attach to  have thin cell walls, no specialized structures, branches (intercalary meristems) and come in a variety of shapes to support their diverse functions.  PLANT TISSUE COMPLEX TISSUE  Ground tissue system is the most extensive, at Complex Tissues least in leaves and young green stems (the pith Xylem - Vessel member, tracheid, fiber, and cortex). parenchyma cell  Vascular tissue system contains two types of Phloem - Sieve-tube member, sieve cell, conducting tissues that distribute water and companion cell, albuminous cell, fiber, sclereid, solutes (xylem) and sugars (phloem) through the parenchyma cell plant body.  Dermal tissue system covers and protects the Epidermis - Guard cell, epidermal cell, subsidiary plant surface (epidermis and periderm). cell, trichome (hair) Periderm - Phellem (cork) cell, phelloderm cell Some of the tissues are composed mostly of a single Secretory structures - Trichome, laticifer cell types and these are called simple tissues. tissues made from aggregates of different cell types are The xylem is a complex tissue made up of different called complex tissues. Tissues, simple or complex, kinds of cells that work together to transport water act together as a unit to accomplish a collective and dissolved minerals. the cell types found in xylem function and are derived from mersitems. are the water-conducting cells - tracheids and vessel members; the vessel members are joined together Plants consist of many different types of cells that are end to end to make vessels; fibers, for strength and organized into aggregates called tissues. support; and parenchyma cells, which help load minerals in and out of the vessel members and Simple and Complex Tissue tracheids SIMPLE TISSUE Simple Tissues Phloem is the tissue that transports sugar through Parenchyma tissue - Parenchyma cell the plant. primary phloem occurs in vascular bundles Collenchyma tissue - Collenchyma cell near the primary xylem in young stems and leaves Sclerenchym tissue - Fiber and in the vascular cylinder in roots. secondary Sclereid phloem occurs outside the secondary xylem in older stems and roots, usually in plants that live longer Parenchyma cells are usually somewhat spherical or than 1 year. elongated, but they may have diverse shapes. they usually have a thin primary cell wall, but they may Epidermis is a complex tissue composed of have a secondary wall, which is sometimes lignified. epidermal cells, guard cells, and trichomes of Lignin is a polymer that is embedded various types. the epidermis is usually one layer of between the cell wall cellulose. cells, but may be as many as five or six layers in the it renders the wall impermeable to water, leaves of some succulent plants and in the aerial so that water movement occurs only roots of certain orchids. the epidermis protects the through openings in the cell wall called inner tissues from drying and from infection by some pits. pathogens. it also regulates the movement of water lignin is also quite hard and strong, making and gases out of and into the plant. lignified cells rigid and supportive even Epidermal cells are the main cell type when the cells are dead. making up the epidermis. Living parenchyma cells found in all plant Young stems, leaves, flower parts, and organs perform the basic metabolic even some roots in exceptional instances functions of cells: respiration, have specialized epidermal cells called photosynthesis, storage, and secretion. guard cells. Trichomes are epidermal outgrowths and Collenchyma is a tissue specialized to support young may be a single cell or multicellular. stems and leaf petioles. its cells often are the The periderm is a protective layer that forms in outermost cells of the cortex, being just inside the older stems and roots after those organs expand epidermis in young stems and the petioles of leaves. and the epidermis splits and is lost. it is a secondary collenchyma cells are elongated, often contain tissue. this tissue is several cell layers deep and is chloroplasts, and are living at maturity. composed of phellem (cork) cells on the outside, a layer of dividing cells (phellogen or cork cambium), Sclerenchyma tissue is composed of cells with rigid and the phelloderm toward the inside. Phellem cells cell walls and they function to support the weight of are dead at maturity and have a waxy substnace a plant organ. there are two types of sclerenchyma (suberin) embedded in their cell walls. cells - fibers and sclereids. these cells tend to have Phelloderm cells live longer than phellem cells and are parenchymalike. thick, lignified secondary cell walls, they are dead at Secretory tissues produce and secrete materials maturity. Secretory structures occur primarily in leaves and stems.  fibers can occur in aggregates forming a continuous cylinder around stems, they may connect end to end to these may be composed of single secretory cells or form multicellular strands acting like strengtheing cables complex multicellular structures. some trichomes, for exactly like re-bar in concrete, or they sometimes appear example, may secrete materials out of the plant to attract as individual cells or small groups of cells as a component insect pollinators. they may also form inside the plant body of vascular tissues. they are long, narrow cells with thick and secrete materials within the plant; cells called laticifers, pitted walls and tapered ends. Fibers are sometimes elastic for example, secrete latex, which discourages herbivores and can be stretched to a degree, but they will snap back from eating the plant. they also form complex ducts inside to their original lengths. wood of trees.  Meristems LESSON 3: The Root System “to divide” Functions of the roots - site in theplant body where new cells form  Absorption of water and nutrients - initiate growth and differentiation  Conduction of absorbed materials into the plant body Growth - irreversible increase in size that comes from cell  Anchorage of the plant in the soil or to a surface division and cell enlargement. Cell differentiation - refers to the changes that a cell  Storage of food undergoes structurally and biochemically so that it can performa specialized function. Types of root system  Tap root system have a main central root upon A meristem is a site in the plant body where new which, small, lateral roots called root hairs are cells form and the complex processes of growth and attached. Carrot, china rose, hibiscus and all differentiation are initiated. growth means the dicots are examples of taproot system. irreversible increase in size that comes from cell divisionand cell enlargement. cell differentiation  Fibrous roots are bushy roots in which thin refers to the changes that a cell undergoes moderately branching roots grow from the structurally and biochemically so that it can perform stem. Rice, wheat, maize, banana and all a specialized function. because cells and tissues are monocots are examples of the fibrous root derived from meristems, we do not consider system. meristems themselves to be tissues, although they Adventitious roots - Plant roots that form from non- are sometimes referred to as meristematic cells and root tissue and are produced both during normal tissues. development and in response to stress conditions, Types of meristems such as flooding, nutrient deprivation, and wounding. What are the categories of meristems, and how do they  Unique category of roots that develop from differ? sources other than the radicle. that is from non- root tissue and are produced both during Root Apical Meristem (RAM) - found at the tip of each root normal development and in response to stress Shoot Apical Meristem (SAM) - found at the tip of each conditions, such as flooding, nutrient branch deprivation, and wounding. Most adventitious - these two apical meristems are the sites of the formation roots arise from stem tissues, but they can also of new cells by cell division. develop from leaves. - called the primary meristems - two roles: form the primary tissues and to elongate the  They are specially numerous on underground root and shoot stems, such as rhizomes, corms, and tubers and are common in most monocotyledons. Primary meristems - originate in apical meristems and Adventitious roots from stem or leaf cuttings differentiate into the primary tissues. The primary make it possible to asexually propagate a wide meristems near the tips of the roots and shoots are the site of most elongation. they produce new cells, which then variety of horticultural plants enlarge primarily by elongation.  Protoderm - epidermis Types of adventitious root  Procambium - primary xylem and primary phloem  Rhizome  Ground meristem - pith and cortex of stems and  Corms roots and the mesophyll of leaves  Tubers  Prop roots or stilt Secondary Meristems - produce the secondary tissues.  Nodular roots The secondary meristems are responsible for cell division,  Haustorium initiation of cell differentiation and growth in a lateral direction, thereby increasing the thickness and  Pneumatophores circumference of stems and roots. The two secondary  Aerial roots meristems: Vascular cambium - differentiates into secondary xylem Development of roots and secondary phloem  Region of cell division (root apical meristem) Cork cambium - differentiates into the periderm  Region of elongation  Region of maturation Other Meristem  regulate elongation The root has an outer layer of cells called the  regulate leaf shape epidermis, which surrounds areas of ground tissues  involved in forming buds and roots in unusual and vascular tissue. The epidermis provides places protection and helps in absorption. root hairs, which  repair of wounds are extensions of root epidermal cells, increase the  ex. intercalary meristem - found at the base of surface area of the root, greatly contributing to the grass leves which allows the leaf to continue to absorption of water and minerals. grow after being grazed or mowed. Inside the root, the ground tissue forms two regions: Vascular cylinder the cortex and little pith. Both regions include cells  Cells of the vascular cylinder were differentiated that store photosynthetic products. the cortex is from the procambium cells. between the epidermis and the vascular tissue,  Entire central cylinder of roots whereas the pith lies between the vascular tissue and the center of the root. Root of a dicot and a monocot The vascular tissue in the root is arranged in the inner portion of the root, which is called the stele. A layer of cells known as the endodermis separates the stele from the ground tissue in the outer portion of the root. the endodermis exclusive to roots, and serves as a checkpoint for materials entering the root’s vascular system. a waxy substance called suberin is present on the walls of the endodermal Protoxylem is capable of transporting water while cells. this waxy region, known as the Casparian strip, the root is elongating, which requires both the forces water and solutes to cross the plasma strength to withstand the forces that move water membranes of the endodermal cells instead of and still be flexible enough to stretch as the root slipping between the cells. this ensures that only elongates. materials required by the root pass through the endodermins, while toxic substances and pathogens Metaxylem cells mature in regions of the root are generally exluded. The outermost cell layer of the where elongation has been completed. because they root’s vascular tissue is the pericycle, an area that are no longer required to elongate, they form thick can give rise to lateral roots. secondary cell walls with pits through which lateral exchange of water and minerals may take place. The Root Cap protoxylem cells often become crushed after the  A group of small, regularly shaped cells metaxylem develop, but by then these cells are not  Actively dividing needed.  Protects the RAM (root apical meristem)  Site for the synthesis of plant hormones Phloem cells form in the areas between the important for controlling root development protoxylem arms. the protophloem is acually the first  Site of gravity perception, which controls the part of the vascular system to vecome functiona. direction of root growth these cells form at the periphery of the phloem and function primarily during root elongation. The Structure of Roots metaphloem develops toward the inside and  Epidermis functions during the plant’s adult life. Phloem of  Cortex roots may consist of parenchyma, fibers, sieve tube  Vascular cylinder members, and companion cells. Epidermis  Differentiated from the protoderm cells  Composed primarily of long epidermal cells  Some develop into root hairs Cortex  Derived from ground meristem  Composed primarily of parenchyma cells  Where the endodermis lies: Endodermis control the movement of nutrient into the xylem Casparian strip Lateral roots ↓ In long-lived dicot plants, the older regions of roots The distribution of the primary vascular bundles form secondary vascular tissues by activating a depends on the position of leaves secondary vascular tissues by activating a secondary meristem, the vascular cambium. Secondary growth Number of vascular bundles in cylinder and number is initiated by the division of pericycle cells and also of leaf traces some leftover or residual procambium cells located  Varies by species between the arcs of xylem and phloem. Residual  Dependent on number and arrangement of procambium cells are actually procambial cells that leaves did not develop into primary xylem or primary phloem. They are now induced to divide, and they Phyllotaxis - phyllo – “leaf”; taxis – “arrangement” form secondary xylem to the inside and phloem to the outside. LESSON 4: The Shoot System The shoot system is the aerial part of the plants. It consists of the branches, leaves as photosynthetic organs, flowers as reproductive organs, and fruits as the carrier of seeds. Modules  Repeating units of the stem  Consists of internode plus the leaf and bud attached to the stem Node - Point of attachment. Functions of Shoot system  Provide axis for attachment of leaves, buds, flowers  To produce new cells, tissues, leaves, and buds  Provide pathways for movement of water and dissolved minerals from roots to leaves  Provide pathways for food synthesized in leaves to move into roots  May be modified for different functions such as water storage Two groups of Flowering Plants  Dicotyledonous plants (dicots) – two cotyledons  Monocotyledonous plants (monocots) – one cotyledon The shoot apical meristem Primary Growth differs in monocot and dicot stems  Vascular bundles in monocot stems are scattered while in dicot stems vb are arranged in rings.  Monocot stem has the same diameter from tip to tip PRIMARY THICKENING MERISTEM (PTM) is unique in contributing to both elongation and lateral growth, a characteristic resulting from its umbrella-like shape. The SAM and the primary meristems are also present in these tips.  Protoderm to epidermis Secondary growth  Ground meristem to pith and cortex  Most monocots show little or no secondary  Procambium to primary xylem and phloem growth Herbaceous (nonwoody) plants The distribution of the primary vascular in dicot Normally complete life cycle in one plants growing season  In vascular cylinder  Dicots and gymnosperms  Leaf traces Display secondary growth starting first year  Bundles that network into attached leaves of growth  Organization of bundles in stems depends on Woody plants  Number and distribution of leaves  Number of traces that branch into leaves into buds Formation of Secondary xylem and phloem Sapwood  Dividing residual procambium between  Lighter wood near periphery bundles called interfascicular cambium  Secondary xylem  Fascicular cambium + interfascicular cambium Has functional xylem cells vascular cambium  Where actual transport of water and dissolved materials takes place Vascular cambium Gymnosperm structure  Only one or two cells thick  Wood – simpler structure  Divide in two directions  Mostly tracheids in axial system and simple  Cells formed to outside form secondary rays phloem  May have resin ducts  Cells formed to inside form secondary xylem Secretory structures that produce and  Typically produces more xylem than phloem transport resin cells Resin  Fusiform initials  Synthesized and secreted by lining of epithelial Cambium cells cells Form into cells of axial system  Sap - Resin flowing through resin ducts to Transport water longitudinally outside of stem  Ray initials  Rosin - Hardened resin Form cells of ray system  Amber - Fossilized rosin Rays composed of ray parenchyma cells and ray tracheids Bark Ray system transports water and minerals Protective covering over wood of tree laterally  Everything between vascular cambium and Wood outside of woody stem  Composed of secondary xylem  composition varies, depending on age of tree  Planes of view Young tree - Secondary phloem, few cortex Tangential section – end view of rays cells, 1 or 2 increments of periderm Radial section – side view of rays Old tree - Layers of secondary phloem and Transverse section – end view of cells of several layers of periderm axial system Annual rings Secondary phloem  Concentric rings of cells of secondary xylem  Forms to outside of vascular cambium  In temperate zones  Cell types One ring/growing season Sieve-tube members, companion cells, determine age of tree by counting rings phloem, parenchyma, phloem fibers,  In tropical rain forests sclereids in axial system, ray parenchyma Irregular growth rings in ray system Growth occurs year round  Cannot count phloem rings to determine age of  Oldest known trees tree Redwoods (Sequioa sempervirens)  Phloem rays Bristlecone pines (Pinus longaeva) Phloem ray parenchyma cells Annual ring components  Springwood or earlywood Periderm Cells in inner part of annual ring  Made up of Cells larger in diameter Phellem cells Formed during first growth spurt of new Cork cambium season Phelloderm cells  Summerwood or latewood  Functions Cells smaller in diameter Inhibits water evaporation Formed later in growing season Protects against insect and pathogen  Ring porous invasion Large diameter vessels mainly in  Cork cambium (phellogen) springwood  New cork cambium usually produced each  Diffuse porous spring Large diameter vessel members uniformly Divides in two directions to produce distributed throughout springwood and  Phellem cells (cork cells) summerwood  Produced toward the outside Heartwood  Phelloderm cells  Darker wood in center  Produced toward the inside  Cells blocked with resins and other materials Phellem cells  No longer functions in transport  Regular rows  Vessel members may be blocked by tyloses  Cell walls contain suberin Form when cell wall of parenchyma cell  Usually dead by time periderm is functional grows through pit and into vessel member Phelloderm cells  Form regular rows  Cells live longer and resemble parenchyma cells Lenticels Stem modifications  In bark of young, woody tree branches  Rhizomes  Loosely packed parenchyma cells Underground stem  Provide area for gas exchange Internodes and nodes Sometimes small, scale-like leaves Girdling  Leaves do not grow  Removal of continuous strip around tree  Leaves are not photosynthetic circumference kills tree Buds in axils of scale leaves elongate,  Nutrient transporting secondary phloem produce new branches which form new severed in process plants Types of bark  Tubers Enlarged terminal portion of underground rhizome Example: potato plant Eyes of tuber – lateral buds  Corms and bulbs Corm  Short, thickened underground stem with thin papery leaves  The ring bark of paper birch trees, forms in  Central portion accumulates stored continuous rings. food to be used at time of flowering  Scale bark, which is characteristic of pine trees,  New corms can form from lateral forms as small overlapping scales. buds on main corm  Shag bark, such as that found in Eucalyptus, has  Example: Gladiolus, Taro long overlapping thin sheets. There are also Bulbs intermediate forms that are useful for tree  Small stem portion identification.  At least one terminal bud (produces Buds new, upright leafy stem)  Short, compressed branches  Lateral bud (produces new bulb)  Covered with hard, modified leaves called bud  Stores food in specialized fleshy scales leaves  Types of buds  Food used during initial growth  Terminal bud spurt At end of branch  Example: Allium cepa  Lateral bud At base of petioles of leaves on side of a  Cladophylls branch Also called cladodes  Flower bud Flattened, photosynthetic stems that Produces flower parts function as and resemble leaves  Bud scale scar Develop from buds in axils of small, scale-  Leaf scar like leaves  Bundle scar  Thorns  Can identify plants in winter by Originate from axils of leaves Structure of leaf scar Help protect plant from predators Number and distribution pattern of bundle May have leaves growing on them scars Spines and prickles Secondary growth in monocot stems  Not modified stems  Most monocots do not form secondary xylem  Spines and secondary phloem  Modified leaves  Palm trees Prickles Exhibit diffuse secondary growth  Modified clusters of epidermal Some thickening of stem from division hairs and enlargement of parenchyma cells  Stolons Not true secondary growth because Also known as runners cambium is lacking Grows horizontally along the ground  Some monocots exhibit true secondary growth Give rise to roots and aerial branches at  Examples – Yucca, Agave (century plant), specialized points called nodes Dracaena (dragon’s blood tree) Forests  Produce stems that are thin at top, thick at  Home to many plants and animals base  Source of raw materials for many useful  Cambium primarily forms parenchyma cells products  Xylem surrounds phloem in vascular bundle  Purify air  Keep soil from washing away  Affect weather patterns Economic value of woody stems Compound leaves  Blade divided into leaflets  Renewable resources  Two types Harvesting of product from plant without  Palmately compound destroying plant Leaflets diverge from a single point Natural rubber, chewing gum, turpentine Example: poison ivy  Nonrenewable resources  Pinnately compound Actual harvesting and use of entire plant Leaflets arranged along an axis  Recycling Examples: coconut leaf, neem leaf Example: recycling paper products  Advantages of compound leaves Helps preserve natural tree resources Spaces between leaflets allow better air flow over surface LESSON 5: The Shoot System II: The Form and  May help cool leaf Structure of Leaves  May improve carbon dioxide uptake Petiole Functions of Leaves  Narrow base of most dicot leaves  Photosynthesis  Leaf without petiole – sessile Release oxygen, synthesize sugars  Vary in shape  Transpiration  Improves photosynthesis Evaporation of water from leaf surface Reduces extent to which leaf is shaded by  Specialized functions other leaves Water storage Allows blade to move in response to air Protection currents Comparison of Monocot and Dicot Leaves Sheath  Formed by monocot leaf base wrapping around blade – portion of leaf that absorbs light energy stem Leaf Blade  Ligule  Broad, flat surface for capturing light and Keeps water and dirt from getting carbon dioxide between stem and leaf sheath  Two types of leaves  Auricles Simple leaves In some grass species Compound leaves Two flaps of leaf tissue Extend around stem at juncture of sheath and blade Why does grass need mowing so often?  Grass grows from base to sheath  Intercalary meristem  Allows for continues growth of mature leaf  Stops dividing when leaf reaches certain age or length Leaf Veins - Vascular bundles composed of xylem and phloem Simple leaves  Leaves with a single blade  Examples Maple Epidermis - Covers entire surface of blade, petiole, Apple and leaf sheath; Continuous with stem Jackfruit epidermis;Usually a single layer of cells. Cell types  Epidermal cells  Guard cells Epidermal cells Formation of New Leaves  Appear flattened in cross-sectional view  Originate from meristems  Outer cell wall somewhat thickened  Leaf primordia – early stages of development  Covered by waxy cuticle  Steps in leaf formation Inhibits evaporation through outer Initiated by chemical signal epidermal cell wall Location in leaf depends on plant’s Stomatal Apparatus phyllotaxis  Cuticle blocks most evaporation Cells at location begin dividing  Opening needed in epidermis for controlled gas  Becomes leaf primordium exchange Shape of new leaf determined by how  Two guard cells + pore → stoma cells in primordium divide and enlarge  Subsidiary cells Leaf form and specialized leaves Surround guard cells May play role in opening and closing pore  Seed leaves (cotyledons)  Guard cells + subsidiary cells stomatal Primarily storage organs apparatus Slightly flattened, often oval shaped  Functions of stoma Usually wither and die during seedling Allows entry of CO2 for photosynthesis growth Allows loss of water vapor by  Cotyledons enlarge and conduct transpiration photosynthesis  Cools leaf by evaporation Heterophylly  Pulls water up from roots  Stomata usually more numerous on bottom of  Different leaf shapes on a single plant leaf  Types of heterophylly  Stomata also found in Related to age of plant Epidermis of young stem Example: Ivy (Hedera helix) Some flower parts  Juvenile ivy leaves – three lobes to leaves Trichomes  Adult ivy leaves – leaves are not  Secretory lobed Stalk with multicellular or secretory head  Environment to which shoot apex is exposed Secretion often designed to attract during leaf development pollinators to flowers Example: marsh plants  Short hairs  Water leaves Hairs store water, reflect sunlight,  Leaves developing underwater insulate leaf against extreme desert heat are thin with deep lobes  Mat of branched hairs  Air leaves Act as heat insulators  Shoot tip above water in Example: olive tree summertime develops thicker  Specialized trichomes leaves with reduced lobing. Leaves modified to eat insects as food  Position of leaf on tree Shade leaves Mesophyll  Develop on bottom branches of tree  Two distinct regions in dicot leaf  Mainly exposed to shade Palisade mesophyll  Leaves are thin with large surface Spongy mesophyll area  Substomatal chamber  Sun leaves Air space just under stomata  Develop near top of same tree  Exposed to more direct sunlight  Leaves are thicker and smaller  Xerophytes Grow in dry climates Leaves designed to conserve water, store water, insulate against heat  Sunken stomata  Thick cuticle  Sometimes multiple layers to Veins epidermis  Dicot midrib (midvein) Abundance of fibers in leaves Xylem in upper part of bundle  Help support leaves Phloem in lower part of bundle  Help leaf hold shape when it dries  Bundle sheath Examples: Single layer of cells surrounding vascular  Oleander (Nerium oleander) bundle  Fig (Ficus) Loads sugars into phloem  Jade plant (Crassula argentes) Unloads water and minerals out of xylem  Mesophytes Grow in moderate climate Leaf Modifications LESSON 6: Plant Growth Regulators  Spines Cells with hard cell wall Hormones Pointed and dangerous to potential  Greek horman = to stimulate predators  A chemical secreted from one organ in the  Tendrils body that influences another organ in specific Modified leaflets ways. Wrap around things and support shoot  often influence the same cells that produce  Bulbs them (as well as others) Thick leaves sometimes referred to as bulb  sometimes called growth regulators scales  Store food and water Plant growth regulators Modified branches with short, thick stem  Auxins and short, thick storage leaves The first plant hormone discovered  Plantlets Auxin is a general term used to indicate Leaves have notches along margins substance that promotes elongation of Meristem develops in bottom of each tissues notch that produce a new plantlet Stimulates internode elongation Plantlet falls off leaf and roots in soil Stimulates initiation of vascular tissue, Form of vegetative (asexual) reproduction fruit growth Example: air-plant (Kalanchoe pinnata) Inhibition of root growth Differentiation of vascular tissue is Leaf Abscission stimulated by IAA  Abscission – separation Auxin stimulates root initiation on stem  Result of differentiation and specialization at cuttings region at base of petiole called abscission zone Stimulates lateral root development in  Weak are due to tissue culture Parenchyma cells in abscission zone are Mediates the tropic response of bending smaller and may lack lignin in cell walls to gravity and light Xylem and phloem cells are shorter in Indoleacetic acid (IAA) vascular bundles at base of petiole  First purified from urine Fibers often absent in abscission zone  A portion of tryptophan is  Abscission zone weakens metabolized to indoleacetic acid and  Cells in vascular bundles become plugged excreted in urine, which is simple a  Leaf falls off waste product. Later the same Scar that remains when leaf falls off substance was found in plant Sealed over with waxy materials which extracts. block entrance of pathogens  Gibberellins  Stimulate the elongation of stem  Abscisic acid internodes. Promoted abscission of cotyledon petioles  Discovered in Japan by studying a disease from their stem. of rice caused by a fungus (Gibberella It inhibits the gibberellins induced fujikuroi) synthesis of amylase and other hydrolytic  Dwarf plants do not make enough active enzymes forms of GA Accumulates in many seeds and helps in  Control flowering in biennial plants seed dormancy  Breaks seed dormancy May prevent transpiration by closing the  Stimulates germination of pollen and stomata, when applied to leaves growth of pollen tubes  Ethylene  Can cause parthenocarpic fruit It is a simple organic molecule present in development or increase the size of the form of volatile gas – in ripening fruits, seedless fruit (grapes) flowers, stems, roots, tubers, seeds.  Cytokinins Present in very small quantity, but its  Modified form of adenine quantity increases during the time of  Found in solutions of boiled DNA and in growth and development coconut milk (liquid endosperm) Responsible for fruit ripening, leaf  Allow cells to divide and grow rapidly as it abscission, stem swelling, leaf bending, stimulates cell division flower petal discoloration and inhibition of  Stimulate growth of lateral roots stem and root growth.  Stimulate leaf expansion resulting from Commercially used for promotion of cell enlargement flowering and fruit ripening, and  May enhance stomatal opening in some stimulation of latex flow in rubber trees. species  Promotes some stages of root development  Delays senescence PLANT PIGMENT  Or biological pigments can be defined as Anthocyanins the biochromes or pigments  Major class of red to blue flavonoid pigments  Substances produced by living organisms  Water soluble and are found in the vacuoles of and have color which results from plant cells absorption techniques.  Used as pH indicators  Set of compounds that have an intense Red in acid, purple/violet in neutral, blue color in alkaline solution  Insoluble substances  Accumulation of anthocyanin attract  Plant pigments give color to leaves, pollinators, and in fruits aid in seed dispersal flowers, and fruits  Protective role against extreme temperatures  Also important in controlling  May protect leaves from attacks by herbivores photosynthesis, growth and development. that may be attracted to green color Four groups of pigments in plants Betalains  Class of red and yellow tyrosine-derived Chlorophyll pigments found in plants of the Caryophyllales  Used to drive photosynthesis (cacti, carnations, amaranths) where they  Most important pigments replace anthocyanin pigments.  Occur in plants, algae, and photosynthetic  Most noticeable in the petals of flowers, but bacteria may color the fruits, leaves, stems and roots of  Different kinds of chlorophyll: a, b, c, d, p plants that contain them.  Beneficial health properties Carotenoids  Two categories of betalains  Yellow, orange, or red pigments Betacyanins – red-colored synthesized by many plants, fungi, and Betaxanthins – yellow-colored bacteria  Can occur in roots, stems, leaves, flowers, Value added products from plant pigment and fruits.  Found in the membrane of plastids  Chlorophyll can be used to color variety of  Beta-carotene and lycopene foods and beverages green such as pasta and  Types of carotenoids spirits Carotenoids with molecules  Betanin is commercially used as a natural food containing oxygen, such as lutein and dye zeaxanthin, are known as  Products of carotenoid degradation such as xanthophylls. ionones, damascones and damascenones are The unoxygenated (oxygen free) also important fragrance chemicals that are carotenoids such as ⍺ -carotene, β- used extensively in the perfumes and fragrance carotene, and lycopene, are known as industry carotenes. Carotenes typically  Dried carrots have the highest amount of contain only carbon and hydrogen carotene which is used as edible product  Anthocyanins from various fruits and vegetables used as food additives  Anthocyanin influences autumn leaf color in many plants which they can used in flower arrangements and dry flower products. IV.H.