Basics of Plant Science PDF

10/8/2023 Basics of Plant Science Dr. Eman Tawfik Associate Professor of Genetics and Genetic Engineering Faculty of Science – Helwan University 1 10/8/2023 2  10/8/2023 The Plan...

10/8/2023 Basics of Plant Science Dr. Eman Tawfik Associate Professor of Genetics and Genetic Engineering Faculty of Science – Helwan University 1 10/8/2023 2  10/8/2023 The Plant Kingdom The concept of plant life The importance of plant science Application of Plants Problems in plants Basic ideas of agronomy, horticulture, pomology, olericulture, …. etc. Classification of plant kingdom 3  10/8/2023 The concept of plant life PLANT PLANT SCIENCE (BOTANY) VEGETATION Types of Plants Herbs, Shrubs, Trees, Climbers, and Creepers. 4 10/8/2023 5 10/8/2023 6 10/8/2023 7  10/8/2023 Importance of Plants 8  10/8/2023 Problems and Disadvantages of plants 9  10/8/2023 Carnivorous plants 10  10/15/2023 Basics of Plant Science Dr. Eman Tawfik Associate Professor of Genetics and Genetic Engineering Faculty of Science – Helwan University Plant Kingdom Includes all the plants Eukaryotic Multicellular Autotrophic organisms Surrounded by rigid cell wall Plants have chloroplast and chlorophyll pigment Photosynthesis 1  10/15/2023 Characteristics of Kingdom Plantae 1. They are non-motile. 2. They make their own food and hence are called autotrophs. 3. They reproduce asexually by vegetative propagation or sexually. 4. These are multicellular eukaryotes. The plant cell contains the outer cell wall and a large central vacuole. 5. Plants contain photosynthetic pigments called chlorophyll present in the plastids. 6. They have different organelles for anchorage, reproduction, support and photosynthesis. 2  10/15/2023 Classification of Kingdom Plantae Classification based on Vascular Seed Plant body system formation Classification of Kingdom Plantae 3  10/15/2023 Cryptogams and Phanerogams The plant kingdom is also classified into two groups: ❑Cryptogams – Non-flowering and non-seed bearing plants. E.g. Thallophyta, Bryophyta, Pteridophyta. ❑Phanerogams – Flowering and seed-bearing plants. E.g. Gymnosperms, Angiosperms. Thallophyta Thallophytes lack a well-differentiated body structure and the plant body is thallus like. They may be filamentous, colonial, branched or unbranched. 4  10/15/2023 Bryophyta do not have vascular tissues. The plant body has root-like, stemlike and leaf-like structures. Ex: Riccia, Marchantia, Funaria, Sphagnum Pteridophyta Pteridophytes have a well-differentiated plant body into root, stem and leaves. They have a vascular system for the conduction of water and other substances. Some of the common examples are Selaginella, Equisetum 5  10/15/2023 Gymnosperms Gymnosperms have a well-differentiated plant body and vascular tissues. They bear naked seeds, i.e. seeds are not enclosed within a fruit. Some of the common examples of gymnosperms are Cycas, Pinus, Ephedra 6  10/15/2023 Angiosperms Angiosperms are seed-bearing vascular plants with a well- differentiated plant body. The seeds of angiosperms are enclosed within the fruits. Angiosperms are widely distributed and vary greatly in size, Angiosperms are divided into monocotyledons and dicotyledons according to the number of cotyledons present in the seeds. Some of the common examples are mango, rose, tomato, onion, wheat, maize 7 10/15/2023 8  10/15/2023 Plant Morphology Plant morphology or phytomorphology: It is the study of the physical form and external structure of plants. In the flowering plants, a plant has two systems Root system & Shoot system. The underground part is called the root while the one above is named the shoot. 9  10/15/2023 Root System The root is o brown, o nongreen and o underground part of a plant. Root with their branches is collectively called a root system. Functions of Root General functions of a root include: ❑Storage. ❑Anchorage. ❑Absorption of water and minerals. ❑Translocation of water and minerals 10  10/15/2023 Shoot System It is the aerial part of the plant, It developed from the plumule of an embryo or the germinating seeds The structure of stem: o branches, o Buds, o leaves, o flowers, o fruits It helps in the conduction of water and minerals. 11  10/15/2023 Function of stem The primary functions of the stem are to support the leaves; conduct water and minerals to the leaves, where they can be converted into usable products by photosynthesis; transport these products from the leaves to other parts of the plant, including the roots. support and elevation of leaves, fruits, and flowers. Plants originated from seeds 12  10/15/2023 Seeds The seed is the beginning and the end of the life cycle of many higher plants A seed is a mature ovule that comprises an embryo or a miniature undeveloped plant and food reserves, all enclosed within a protective seed coat. Seeds are a way of reproduction for all flowering plants. Seed Formation 13  10/15/2023 Seed Dispersal Seed Structure 1. Seed Coat 2. Endosperm 3. Embryo 14  10/15/2023 Types of Seeds 15  10/15/2023 Seed Function They help in germination of the new plant. The seeds contain food reservoirs in the form of cotyledons and endosperm. The seed coat is protective in nature which protects the embryo inside Seed germination 16  10/15/2023 Next Seed germination in details 17  10/23/2023 Basics of plant science Plant Morphology Dr. Eman Tawfik Associate professor of Genetics and Genetic Engineering Seed germination may be defined as the:- fundamental process by which Seed different plant species grow from Germination a single seed into a plant. This process influences both crop yield and quality. 1  10/23/2023 The Process of Seed Germination 2  10/23/2023 The Process of Seed Germination Stage 1: Imbibition The seeds take up water rapidly and this results in swelling and softening of the seed coat at an optimum temperature. Activation of enzymes and internal physiological processes. Stage 2: Emergence By rupturing of the seed coat, radicle emerges to form a primary root. The seed starts absorbing underground water. After the emerging of the radicle and the plumule, shoot starts growing upwards. Stage 3: Elongation In the final stage of seed germination, the cell of the seeds become metabolically active, elongates and divides to give rise to the seedling Types of Seed Epigeal Germination Hypogeal Germination Germination 3  10/23/2023 What is Epigeal Germination? In seeds with epigeal germination, the cotyledons are brought above the soil due to elongation of the hypocotyl. Here the cotyledons, besides food storage, also perform photosynthesis till the seedling becomes independent. Ex.: castor, cotton, papay, onion, beans. Pros and Cons of Epigeal Germination Young leaves are protected by the cotyledons. Advantages Opportunity for early photosynthesis The cotyledons turn green and manufacture additional food for are: the seedling. The plant establishes itself quickly due to initial rapid growth. Disadvantages The plant can be grazed early and die. are:- 4  10/23/2023 What is Hypogeal Germination? Hypogeal germination is a type of seed germination, which is typical for both the monocot and dicot seeds, where the cotyledons remain inside the soil. Ex: maize, pea, and coconut. Pros and Cons of Hypogeal Germination Advantages The plant or the seedlings are protected from early grazing and the are: drawback Disadvantages The plant cannot begin to synthesize its own food or photosynthesize until the are:- true leaves have completely appeared 5  10/23/2023 Factors Affecting Seed Germination External factors Water (moisture) Temperature Oxygen Light Salinity Pathogens Internal factors Seed dormancy Seed Dormancy Seed dormancy is defined as the inability of a viable seed to germinate under conditions favorable for germination. These conditions are the combination of light, water, oxygen, temperature, humidity, gases, mechanical restrictions such as types of the seed coat and hormones. The period of seed dormancy may vary from days to months and even years. 6  10/23/2023 Plant Morphology – Plant Body Root System Roots are the important underground part of all vascular plants. Function of roots:- Anchoring plant down into the ground and Absorbing the essential mineral elements, nutrients, and water from the soil. Translocation of these nutrients to other plant parts It is also used to store food Phytohormones secretion Reproduction: Even though roots are not the reproductive part of plants, they are vegetative parts. In some plants, the roots are a means of reproduction. For instance, new plants arise from creeping horizontal stems called runners (stolons) in jasmine, grass, etc. This type of reproduction is called vegetative propagation. 7  10/23/2023 Parts of Roots Types of Roots Tap roots Advantageous roots Normal Fibrous Storage Proper Fusiform Storage Napiform Aerial Conical Respiratory Haustorial Contractile 8  10/23/2023 Shoot System Shoot system is an aerial and erect part of plant body which grows upwards. It is usually above the soil and develops from plumule of the embryo. It consists of: stem, bud, branches, leaves, flowers, fruits and seeds. Characteristics of Stem Arises as a prolongation of plumule (one end of an embryo). Grows and bends towards light (positively phototropic) and away from gravity (negatively geotropic). Divided into nodes (point of attachment of leaf) and internodes (regions between two nodes). Bears leaves, branches and flowers on nodes. Bears vegetative buds which could be terminal (apical bud) for plant to grow upwards or axillary (bud in the axil of leaf) which give rise to lateral branches. Bears floral buds (terminal or axillary) that grow into flowers. Sometimes make photosynthesis 9  10/23/2023 Stem It functions as a skeleton by constituting a major part of the shoot system and firmly supports the other components like leaves, buds, flowers and fruits. The main stem originates through the direct prolongation of the embryo and gives rise to the lateral stems, leafy appendages, buds etc. Stem Structure 10  10/23/2023 Types of Stem in Plants (i) aerial (erect, rigid, strong and upright as in herbs, shrubs and trees) (ii) sub aerial (weak, unable to stay upright and trail on ground as creepers or climb up as climbers) or (iii) underground (buried in soil and produces aerial branches under favorable conditions only). Stem modification Aerial o Cladode (photosynthesis) o Phylloclade (photosynthesis) o Tendrils (support) o Spines (protection) Underground o Rhizome o Tuber o Corms o Bulb 11  10/23/2023 Leaves These are the flattened structures responsible mainly for photosynthesis. It hits the node of the main stem and the region in the middle of two nodes or internode. The angle forming between the leaf at the node section and the vertical stem commonly refers to the “Leaf axil” 12  10/23/2023 Leaf Structure Leaf base: It fixes the leaf to the stem’s node. Petiole: It is a stalk-like appendage that joins a leaf base to the leaf lamina. Leaf lamina: It is the leaf blade that comprises the midrib, veins and veinlets Types of Leaves Simple Lopped Compound 13 10/23/2023 14  10/23/2023 Buds A bud is meristematic tissue which occurs on the tip of a branch or at a stem node at the axil of a leaf where it will develop into a new shoot or flower. Types of Buds According to position o Apical (Terminal) o Lateral (Axillary) o Adventitious Bud According to season o Winter o Summer According to Function o Vegetative Bud o Reproductive Bud o Mixed Bud 15  10/23/2023 Flower Flower Structure Calyx o Sepals Corolla o Petals Androecium o Stamen ▪ Anther ▪ Filament Gynoecium o Carpel ▪ Stigma ▪ Style ▪ Ovary 16  10/23/2023 Fruits A fruit is a mature fertilized ovary and its associated parts. It usually contains seeds, which have developed from the enclosed ovule after fertilization. 17 10/23/2023 18  10/29/2023 Plant Anatomy “Plant Cell” Dr. Eman Tawfik Associate professor of Genetics and Genetic Engineering Plant Anatomy Plant anatomy is the study of the tissue and cell structure of plant organs. The term anatomy, as applied to plants, generally deals with structures that are observed under a high- powered light microscope or electron microscope. 1  10/29/2023 Plant Organization Cells serve as the fundamental building block of plants. Cells are organized into tissues, which are then organized into organs. Plant organs differ from one another in terms of their internal structure. 2  10/29/2023 Plant Cell Structure The plant cell is the basic building unit in plant Plant cell structure Cell wall Protoplast o Protoplasmic (Living) components ❑ Cytoplasm ❑ Nucleus ❑ Plastids ❑ Mitochondria ❑ Golgi apparatus o Non-protoplasmic (Non-living) components ❑ Vacuoles ❑ Ergastic substances ✓ Carbohydrates (Starch) ✓ Protein ✓ Fatty acids ✓ Enzymes ✓ Phytohormones ❑ Minerals ❑ Ca. Carbonates ✓ Cystolith ❑ Ca. oxalates ✓ Solitary ✓ Raphides ✓ Druses 3  10/29/2023 Cell Wall It is a rigid layer which is composed of polysaccharides cellulose, pectin and hemicellulose. It is located outside the cell membrane. It also comprises glycoproteins and polymers such as lignin, cutin, or suberin. The primary function of the cell wall is to protect and provide structural support to the cell. The plant cell wall is also involved in protecting the cell against mechanical stress and providing form and structure to the cell. It also filters the molecules passing in and out of it. The formation of the cell wall is guided by microtubules. It consists of three layers, namely, primary, secondary and the middle lamella. The primary cell wall is formed by cellulose laid down by enzymes. 4  10/29/2023 The function of the plant cell wall I- Rigid structure that defines shape of cell. 2- Provides rigidity and strength to plants. 3- Allows plants to grow tall and withstand forces such as wind& gravity 4- Allows cells to build up internal (turgor) pressure which adds stiffness to cell/plant 5  10/29/2023 Cell membrane (Plasma membrane) It is the semi-permeable membrane that is present within the cell wall. It is composed of a thin layer of protein and fat. The cell membrane plays an important role in regulating the entry and exit of specific substances within the cell. For instance, cell membrane keeps toxins from entering inside, while nutrients and essential minerals are transported across. 6  10/29/2023 Functions of the plant cell (plasma) membrane In-plant cells the cell membrane separated the cytoplasm from the cell wall. It has a selective permeability hence it regulates the contents that move in and out of the cell. It also protects the cell from external damage and provides support and stability to the cell. It has embedded proteins which are conjugated with lipids and carbohydrates, along the membrane, used to transport cellular molecules. Protoplasmic (living) components 7  10/29/2023 Cytoplasm This is a gel-like matrix lying just below the cell membrane, housing most of the cell organelles. It is made up of water, enzymes, salts, organelles, and various organic molecules. Function: a physical medium for holding and housing most of the complex cell’s interior organelles and being a medium for transporting and processing cell molecules for maintaining cell life. The cytoplasm of the plant houses several organelles including Plastids, Mitochondria, Central vacuoles, Endoplasmic reticulum, Golgi bodies, Storage granules, lysosomes. Plastids Plastid is a double membrane-bound organelle involved in the synthesis and storage of food, commonly found within the cells of photosynthetic plants. They are necessary for essential life processes, like photosynthesis and food storage. A plastid containing green pigment (chlorophyll) is called chloroplast whereas a plastid containing pigments apart from green is called a chromoplast. A plastid that lacks pigments is called a leucoplast and is involved mainly in food storage. 8 10/29/2023 9  10/29/2023 General functions of plastids They are actively involved in manufacturing food for the plant by photosynthesis due to the presence of chlorophyll pigment in the chloroplast. They also store food in the form of starch. They have the ability to synthesize fatty acids and terpenes that produces energy for the cell’s mechanisms. Palmitic acid, a component synthesized by chloroplasts is used in manufacturing the plant cuticle and waxy materials. Mitochondria They are the double-membraned organelles found in the cytoplasm of all eukaryotic cells. They provide energy by breaking down carbohydrate and sugar molecules, hence they are also referred to as the “Powerhouse of the cell.” The mitochondria convert stored nutrients by the help of oxygen to produce energy in for of (ATP )Adenosine TriPhosphate, hence they are the site for non-photosynthetic energy transduction. 10  10/29/2023 Endoplasmic reticulum (ER) It is made up of two regions known as the rough endoplasmic reticulum (they have ribosomes attached to their surface membrane) and the smooth endoplasmic reticulum (they lack ribosomal attachment). The endoplasmic reticulum known for its high dynamics functions in eukaryotic cells, play major roles in synthesizing, processing, transporting and storing proteins, lipids, and chemical elements. These elements are used by the plant cell and other organelles such as the vacuoles and the apoplast (Plasma membrane). The primary role of the Rough ER in synthesizing proteins, which are transported from the cell to the Golgi bodies, which carry them to other parts of the plant to help in its growth. 11  10/29/2023 Ribosomes This is the organelle responsible for protein synthesis of the cell. Its found in the cell cytoplasm in large numbers and a few of them called functional ribosomes can be found in the nucleus, mitochondria, and the cell chloroplast. Its made up of ribosomal DNA (rDNA) and cell proteins The process of protein synthesis by the ribosomes is known as translation, by using the messenger RNA, which delivers the nucleotides to the ribosomes. The ribosomes then guide and translate the message in the form of nucleotides, contained by the mRNA. 12  10/29/2023 Golgi bodies Golgi bodies are maintained together by cytoplasmic microtubules and clasped by a protein matrix They are made up of flattened stacked pouches known as cisternae. Plant cells have a few hundreds of the Golgi bodies moving along the cell’s cytoskeleton, over the endoplasmic reticulum as compared to the very few found in animal cells The Golgi bodies have several functions linked to them, from being an adjacent organelle to the endoplasmic reticulum to where they deliver the cell products to. 13  10/29/2023 Golgi Apparatus They are found in all eukaryotic cells, which are involved in distributing synthesized macromolecules to various parts of the cell. 14  10/29/2023 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 through 15  10/29/2023 Non-protoplasmic (Non-living) components Plant Vacuoles Plant cells have large vacuoles as compared to animal cells. The central vacuoles are found in the cytoplasmic layer of cells of a variety of different organisms, but larger in the plant cells. 16  10/29/2023 Function of Vacuoles The vital function of the central vacuole apart from storage is to sustain turgor pressure against the cell wall. The central vacuole consists of cell sap. It is a mixture of salts, enzymes and other substances. Macromolecules in plant cell ❑Biological macromolecules are important cellular components and perform a wide array of functions necessary for the survival and growth of living organisms. The four major classes of biological macromolecules are carbohydrates, lipids, proteins, and nucleic acids. Proteins o Amino acids Carbohydrates o Monosaccharides (Glucose) o Disaccharides (Sucrose) o Polysaccharides (Starch) Lipids o Fatty acids Nucleic acids o DNA o RNA 17  10/29/2023 Minerals in plant cells ❑Minerals in plants: can be divided into macro- and micro-elements Nine macro-elements: ✓Carbon (C), Oxygen (O), Hydrogen (H), Nitrogen (N), Phosphate (P), Potassium (K), Calcium (Ca), Magnesium (Mg), and Sulfur (S), and eight micro-elements: ✓Iron (Fe), Manganese (Mn), Copper (Cu), Borium (B), Zinc (Zn), Molybdenum (Mo), Chlorine (Cl) and Nickel (Ni) although Ni is only required in low amount and not all plants need Ni. Cells are divided according to Age Position Function 18  10/29/2023 Plant Cell Types Meristematic cells Permanent cells o Simple cells ✓ Parenchyma ✓ Collenchyma ✓ Sclerenchyma o Compound cells ✓ Epidermal ✓ Xylem ✓ Phloem 19  10/29/2023 Meristematic cells They are responsible for the root and shoot growth of plants. These cells have the ability to divide and increase in number and increase the length as well as the girth of the stem and root. Meristematic cells are found in many locations, including near the tips of roots and stems (apical meristems), in the buds and nodes of stems, in the cambium between the xylem and phloem in dicotyledonous trees and shrubs, under the epidermis of dicotyledonous trees and shrubs (cork cambium), and in the pericycle Parenchyma Cells Parenchyma cells play a significant role in all plants. They are the living cells of plants, which are involved in the production of leaves. They are also involved in the exchange of gases, production of food, storage of organic products and cell metabolism. These cells are typically more flexible than others because they are thinner. 20  10/29/2023 Collenchyma Cells They are hard or rigid cells, which play a primary role in providing support to the plants when there is restraining growth in a plant due to lack of hardening agent in primary walls. 21  10/29/2023 Sclerenchyma Cells These cells are more rigid compared to collenchyma cells and this is because of the presence of a hardening agent. These cells are usually found in all plant roots and mainly involved in providing support to the plants. Parenchyma: living cells, non-lignified. Collenchyma: living, lignified (external lignification). Sclerenchyma: non-living, lignified (internal and external lignification) 22  10/29/2023 Xylem and Phloem Xylem: water and minerals translocation Phloem: carbohydrate translocation 23 10/29/2023 24  11/2/2024 Cell Division and Organization Dr. Eman Tawfik Associate professor of Genetics and Genetic Engineering 1 Nucleus 2 1  11/2/2024 Typically, it is the most evident organelle in the cell. The nucleus is completely bound by membranes. It is engirdled by a structure referred to as the nuclear Structure envelope. Of Nucleus The membrane distinguishes the cytoplasm from the contents of the nucleus The cell’s chromosomes are also confined within it. DNA is present in the Chromosomes, and they provide the genetic information required for the creation of different cell components in addition to the reproduction of life. 3 Nucleus Function It contains the cell’s hereditary information and controls the cell’s growth and reproduction. The nucleus has been clearly explained as a membrane-bound structure that comprises the genetic material of a cell. It is not just a storage compartment for DNA, but also happens to be the home of some important cellular processes. First and foremost, it is possible to duplicate one’s DNA in the nucleus. This process has been named DNA Replication and produces an identical copy of the DNA. Producing two identical copies of the body or host is the first step in cell division, where every new cell will get its own set of instructions. Secondly, the nucleus is the site of transcription. Transcription creates different types of RNA from DNA. Transcription would be a lot like creating copies of individual pages of the human body’s instructions which may be moved out and read by the rest of the cell. The central rule of biology states that DNA is copied into RNA, and then proteins. 4 2  11/2/2024 Nucleus = Nucleolus + Chromatin Chromatin = DNA + Histones DNA (polymer): Nucleotide is the monomer unit Nucleotide = Pentose sugar + PO4-3 + N. bases Nitrogen bases = Purine (A & G) and Pyrimidine (C, T, U) Pairing : A=T , CⱻG 5 6 3  11/2/2024 7 8 4  11/2/2024 Nucleolus Contained within the nucleus is a dense, membrane- less structure composed of RNA and proteins called the nucleolus. Some of the eukaryotic organisms have a nucleus that contains up to four nucleoli. The nucleolus contains nucleolar organizers, which are parts of chromosomes with the genes for ribosome synthesis on them. The nucleolus helps to synthesize ribosomes by transcribing and assembling ribosomal RNA subunits. These subunits join together to form a ribosome during protein synthesis. The nucleolus disappears when a cell undergoes division and is reformed after the completion of cell division. 9 Functions of chromatin 1. Packaging of large sized DNA into small volume nucleus. 2. Strengthening of DNA for mitosis and meiosis. 3. Protects DNA from damage. 4. Control of gene expression. 10 5  11/2/2024 11 12 6  11/2/2024 13 Chromosomes The nucleus is the organelle that houses chromosomes. Chromosomes consist of DNA, which contains heredity information and instructions for cell growth, development, and reproduction. Chromosomes are present in the form of strings of DNA and histones (protein molecules) called chromatin. When a cell is “resting” i.e. not dividing, the chromosomes are organized into long entangled structures called chromatin. The chromatin is further classified into heterochromatin and euchromatin based on the functions. The former type is a highly condensed, transcriptionally inactive form, mostly present adjacent to the nuclear membrane. On the other hand, euchromatin is a delicate, less condensed organization of chromatin, which is found abundantly in a transcribing cell. 14 7  11/2/2024 8 Regions of chromosome Chromatid Centromere Satellite Pellicle Matrix Chromonemata Centromere Telomer 15 Chromatid It is one half of the replicated or duplicated chromosome or one of the two identical halves of a replicated or duplicated chromosome. A replicated chromosome has a duplicated copy attached to itself. So, a duplicated chromosome has two chromatids which are attached at their centromere and are known as sister chromatids, which are genetically identical. 16 8  11/2/2024 Centromere It is also called the primary constriction. It is the point where sister chromatids are attached. It is the constricted region from where chromosome's arms (chromatids) originate; a short arm (p arm) and a long arm (q arm). It is the link between two sister chromatids. Centromere gives the chromosome its unique shape that helps understand its structure and location of genes. The position of centromere also helps categorize chromosomes into different types. 17 Secondary constriction It is the constricted region on the chromosome other than the primary constriction or centromere. It can be located at any point of the chromosome. It marks the location where nucleoli are assembled and reorganization or formation of nucleolus takes place in the interphase of a cell cycle at the end of the cell division. So, it is also known as nucleolar organizing region (NOR). The nucleolus is formed around the NOR region. 18 9  11/2/2024 Satellite It is a knob-like structure at the end of a chromosome It is between the secondary It is also called Trabant or that is present beyond the constriction and the satellite body. secondary constriction or telomere. distal to it. It also helps identify a The chromosomes with Its size may vary as per the chromosome from a set of satellite are also called position of the secondary chromosomes as its position satellite or sat- constriction. remains the same for a chromosomes. particular chromosome. 19 It is the membrane that encloses the chromosomes. Each chromosome is bounded by a pellicle, which is very thin and is made up of achromatic (non- genetic) material. Pellicle 20 10  11/2/2024 It is the jelly-like ground substance of chromosomes that is enclosed by pellicle. It is an achromatic (non- genetic) material and contains the chromonemata. Matrix 21 (singular-chromonema): They are the spirally coiled central filaments embedded in the matrix of the chromosome. Along its length, the chromomeres are aligned. The Chromonemata chromonemata are so tightly packed that they look like a single filament or thread with a thickness of around 800 Angstrom. 22 11  11/2/2024 It is one of the serially arranged beads or granules aligned along the chromonemata. It is a dense mass of coiled chromatin located Chromomere at fixed intervals along the length of chromonema thread. Chromomeres on a chromonema look like beads on a string. 23 It is the tip or terminal end of the chromosome. It is different in structure and composition from the rest of the chromosome. It prevents the end of a chromosome from sticking to the Telomere ends of other chromosomes. However, it is a modified part of the chromosome that attaches to the nuclear membrane. They are made of the same sequence of bases which is repeated again and again. The telomere sequence in humans is TTAGGG. 24 12  11/2/2024 i) Chromosome types based on the number of centromeres present on a chromosome: Monocentric: This type of chromosome has only one centromere. Dicentric: It has two centromeres. Types of Polycentric: It has more than two centromeres. chromosomes Acentric: It does not have any centromere. Such chromosomes are freshly broken segments of chromosomes that do not survive for long. Diffused or non-located: It does not have distinct centromere. Its centromere is diffused throughout the length of the chromosomes. 25 ii) Chromosomes types based on the location of the centromere on a chromosome: 26 13  11/2/2024 Autosomes: In a human cell out of the 46 chromosomes (23 pairs), 44 chromosomes (22 pairs) are autosomes. They control the iii) Types of somatic characteristics of an organism such as Chromosomes body weight, height, colour, etc. They play no role in determining the sex of an individual. based on their function: Sex chromosomes: One out of the 23 pairs of the chromosomes or the last pair of the chromosomes in a human cell, which help in determining the sex of an individual, is called sex chromosomes. If the pair has identical chromosomes (XX), the individual is a female. 27 Cell division happens when a parent cell divides into two or more cells called daughter cells. Cell Division In other words, such cycles of growth and division allow a single cell to form a structure consisting of millions of cells. 28 14  11/2/2024 Mitosis: The process cells use to make exact replicas of themselves. Mitosis is observed in almost all the body’s cells (somatic cells), including eyes, skin, hair, and muscle cells. Types of Cell Meiosis: In this type of cell division, sperm or egg cells are produced instead of identical Division daughter cells as in mitosis. Occurs in gonads cells. Binary Fission (Amitosis): Single-celled organisms like bacteria replicate themselves for reproduction. 29 Types of cell division Amitosis Direct Division Mitosis In Direct Division Meiosis Reduction Division 30 15  11/2/2024 Amitosis Cell division by simple cleavage of the nucleus and division of the cytoplasm without spindle formation or appearance of chromosomes. 31 Mitosis is a process of cell duplication, in which one cell divides into two genetically identical daughter cells. In the various stages of mitosis, the What is mitosis? cell's chromosomes are copied and then distributed equally between the two new nuclei of the daughter cells. 32 16  11/2/2024 Features of Mitosis In each cycle of cell division, two daughter cells are formed from the parent cell. The cell is also known as equational cell division because the chromosome number in the parent cell and daughter cell is the same. In plants, mitosis leads to the growth of vegetative parts of the plant like root tip, stem tip, etc. Segregation and combination do not occur in this process. 33 Interphase Prophase Stages of Metaphase Mitosis Anaphase Telophase 34 17  11/2/2024 Interphase Before entering mitosis, a cell spends a period of its G1 Phase: This is the period growth under interphase. It before the synthesis of DNA. undergoes the following phases when in interphase: G2 Phase: This is the phase S Phase: This is the phase between the end of DNA during which DNA synthesis synthesis and the beginning takes place. of the prophase. 35 36 18  11/2/2024 Prophase immediately follows the S and G2 phases of the cycle and is marked by condensation of the genetic material to form compact mitotic chromosomes composed of two chromatids attached at the Prophase centromere. The completion of the prophase is characterized by the initiation of the assembly of the mitotic spindle, the microtubules and the proteinaceous components of the cytoplasm that help in the process. The nuclear envelope starts disintegrating. 37 At this stage, the microtubules start pulling the chromosomes Metaphase with equal force and the chromosome ends up in the middle of the cell. This region is known as the metaphase plate. Thus, each cell gets an entire functioning genome. 38 19  11/2/2024 The splitting of the sister chromatids marks the onset of anaphase. These sister chromatids become the chromosome of the daughter nuclei. The chromosomes are then pulled towards the pole by the fibres attached to Anaphase the kinetochores of each chromosome. The centromere of each chromosome leads at the edge while the arms trail behind it. 39 The chromosomes that cluster at the two poles start coalescing Telophase into an undifferentiated mass, as the nuclear envelope starts forming around it. The nucleolus, Golgi bodies and ER complex, which had disappeared after prophase start to reappear. 40 20  11/2/2024 Functions of Mitosis Following are the two important functions of mitosis: Mitosis helps in the development of an organism. In single-celled organisms, mitosis is the process of asexual reproduction. Mitosis helps in the replacement of damaged tissues. The cells near the damaged cells begin mitosis when they do not sense the neighboring cells. The dividing cells reach each other and cover the damaged cells. 41 42 21  11/2/2024 43 44 22  11/2/2024 Meiosis Meiosis is sometimes called Meiosis is a type of cell division "reduction division" because it in sexually reproducing reduces the number of organisms that reduces the chromosomes to half the normal number of chromosomes in number so that, when fusion of gametes (the sex cells, or egg and pollen grain and egg occurs, baby pollen grain). will have the correct number. 45 The main function of the What is meiotic division is the meiosis production of gametes function? (egg cells or pollen grain cells) or spores. 46 23  11/2/2024 What are the stages of meiosis in order? The major phases of meiosis including: Meiosis I interphase, prophase I, metaphase I, anaphase I, telophase I & cytokinesis, Meiosis II interphase II, metaphase II, anaphase II, and telophase II. cytokinesis 47 Meiosis I The first meiotic division is a reduction division (diploid → haploid) in which homologous chromosomes are separated P-I: Chromosomes condense, nuclear membrane dissolves, homologous chromosomes form bivalents, crossing over occurs M-I: Spindle fibers from opposing centrosomes connect to bivalents (at centromeres) and align them along the middle of the cell A-I: Spindle fibers contract and split the bivalent, homologous chromosomes move to opposite poles of the cell T-I: Chromosomes decondense, nuclear membrane may reform, cell divides (cytokinesis) to form two haploid daughter cells 48 24  11/2/2024 Meiosis II The second division separates sister chromatids (these chromatids may not be identical due to crossing over in prophase I) P-II: Chromosomes condense, nuclear membrane dissolves, centrosomes move to opposite poles (perpendicular to before) M-II: Spindle fibers from opposing centrosomes attach to chromosomes (at centromere) and align them along the cell equator A-II: Spindle fibers contract and separate the sister chromatids, chromatids (now called chromosomes) move to opposite poles T-II: Chromosomes decondense, nuclear membrane reforms, cells divide (cytokinesis) to form four haploid daughter cells The final outcome of meiosis is the production of four haploid daughter cells These cells may all be genetically distinct if crossing over occurs in prophase I (causes recombination of sister chromatids) 49 50 25  11/2/2024 51 In prophase I, homologous chromosomes undergo a process called synapsis, whereby they pair up to form a bivalent (or tetrad) Crossing over The homologous chromosomes are held together at points called (Synapsis) chiasmata (singular: chiasma) Crossing over of genetic material between non-sister chromatids can occur at these chiasmata As a result of this exchange of genetic material, new gene combinations are formed on chromatids (recombination) Once chiasmata are formed, the homologous chromosomes condense as bivalents and then are separated in meiosis If crossing over occurs then all four haploid daughter cells will be genetically distinct (sister chromatids are no longer identical) 52 26  11/2/2024 53 Cytokinesis is the physical process of cell division, which divides the cytoplasm of a parental cell into two daughter cells. It occurs concurrently with two types of nuclear division called mitosis and meiosis. Cytokinesis What is the simple definition of cytokinesis? cytokinesis, in biology, the process by which one cell physically divides into two cells. 54 27  11/2/2024 55 56 28  11/2/2024 https://www.youtube.com/watch?v=5bq1To_RKEo https://www.youtube.com/watch?v=kQu6Yfrr6j0 https://www.youtube.com/watch?v=5bq1To_RKEo Essential https://www.youtube.com/watch?v=-PfVNZedmGA Links https://www.youtube.com/watch?v=kQu6Yfrr6j0 https://www.youtube.com/watch?v=Gq2SQMkg4w4 https://www.youtube.com/watch?v=-PfVNZedmGA https://www.youtube.com/watch?v=QRZsBANBUpk https://www.youtube.com/watch?v=Gq2SQMkg4w4 57 Thank you 58 29  11/26/2023 Plant permanent tissues DR. EMAN TAWFIK ASSOCIATE PROFESSOR OF GENETICS AND GENETIC ENGINEERING FACULTY OF SCIENCE – HELWAN UNIVERSITY 1 2 1  11/26/2023 3 Plant Tissue System A tissue is a cluster of cells, that are alike in configuration and work together to attain a specific function. Different types of plant tissues include permanent and meristematic tissues. 4 2  11/26/2023 Meristematic tissue: These tissues have the capability to develop by swift division. They assist in the major growth of the vegetation. Growth in length and growth in diameter of the plant is carried about by these cells. The Meristematic cells are cubical, living cells with a big nucleus. These cells are meticulously crammed with no intercellular spaces. Depending on the section where the meristematic tissues are existing, they are categorized as intercalary, lateral and apical meristems. Apical meristem is existent at the growing tips or apical of stems and roots. Apical meristem upsurges the length of the plant. Lateral meristem is existent in the radial portion of the stem or root. Lateral meristem upsurges the thickness of the plant. Intercalary meristem is found at the internodes or at the base of the leaves. Intercalary meristem upsurges the size of the internode. 5 Permanent tissues: These cells have lost their ability to distribute but are specialised to offer elasticity, flexibility and strength to the plant. These tissues can be additionally categorized into: 1. Simple Permanent Tissue: They can be classified into sclerenchyma, collenchyma and parenchyma based on their purpose. 2.Complex Permanent Tissue: These tissues include phloem and xylem. Xylem is valuable for the transportation of water and solvable constituents. It is made up of xylem parenchyma, fibres, vessels and tracheids. Phloem is valuable in the transportation of food particles. Phloem consists of phloem parenchyma, phloem fibres, companion cells, sieve cells and sieve tubes. 6 3  11/26/2023 Parenchyma These are alive, polygonal cells with a big central vacuole, and have intercellular spaces amidst them. Parenchymatous cells create ground tissue and pith. 1. Parenchyma consisting of chloroplasts are termed as chlorenchyma. The chlorenchyma helps in photosynthesis. 2. Parenchyma which consists of big air voids is called aerenchyma. Buoyancy is the main purpose the aerenchyma. 3. Some parenchymatous cells perform as storage chambers for starch in vegetable and fruits. 4. Living and non-lignified 7 Types of parenchyma cells 8 4  11/26/2023 Collenchyma These are stretched out, living cells with minute intercellular gaps. Their cell walls are made up of pectin and cellulose. Collenchyma is found in the marginal regions of leaves and stems and offers flexibility with the structural framework and mechanical support to plants. Living – Lignified (external lignification). 9 Sclerenchyma These are elongated, dead cells with lignin deposits in their cell wall. They have no intercellular gaps. Sclerenchyma is found in the covering of seeds and nuts, around the vascular tissues in stems and the veins of leaves. Sclerenchyma provides strength to the plant. Non-living – external and internal lignification 10 5  11/26/2023 11 Types of Xylem lignification 12 6  11/26/2023 Dermal Tissues (The epidermis) It is the outer protective layer of the primary plant body (the roots, stems, leaves, flowers, fruits, and seeds). The epidermis is usually one cell layer thick, and its cells lack chloroplasts 13 Protective tissues (Dermal Tissue) These provide fortification to the plant. They include the cork and epidermis. 1. Epidermis – It is a layer of cell that makes up an outer casing of all the structures in the plant. The stomata perforates the epidermis at certain places. The stomata help in loss of water and gaseous exchange. 2.Cork – This is the external protective tissue, which substitutes the epidermal cells in mature stems and roots. Cork cells are lifeless and lack intercellular gaps. Their cell walls are coagulated by suberin, which makes them impervious to gas and Water Molecules. 14 7  11/26/2023 15 16 8  11/26/2023 17 18 9  11/26/2023 19 20 10  11/26/2023 Types of Stomata Kidney-shaped stomata ❑ Kidney shaped guard cells are present in dicot plants inner wall of guard cells are boundaries an outer wall inner wall is thicker than the outer wall. Dumbell-shaped stomata ❑ In monocot plants dumbbell-shaped stomata are present but in case of Cyperus, both kidney and dumbbell-shaped guard cells are present. 21 22 11  11/26/2023 Functions of Stomata Gaseous exchange- Stomatal opening and It helps in transpiration and The main functions of closure help in the gaseous removal of excess water in stomata are: exchange between the plant the form of water vapour. and surrounding. It maintains the moisture Stomata facilitate carbon Stomatal closure at night balance according to dioxide uptake and release prevents water from weather by opening and of oxygen during the escaping through pores. closing. process of photosynthesis. 23 24 12  11/26/2023 25 26 13  11/26/2023 Xylem It helps in the transport of dissolved substances and water all through the plant. The diverse components of the xylem include vessels, tracheids, xylem fibres and xylem parenchyma. Xylem fibres and Tracheids are made up of lignin, which provides structural support to the plant. Phloem This tissue helps in the transportation of food all through the plant. The diverse elements of phloem include phloem fibres, sieve tubes, phloem parenchyma and companion cells. 27 28 14  11/26/2023 29 30 15  11/26/2023 31 32 16  11/26/2023 33 34 17  11/26/2023 35 36 18  11/26/2023 37 38 19  11/26/2023 39 40 20  11/26/2023 41 42 21  11/26/2023 43 44 22  11/26/2023 Types of tissues in leaves 1. Stomatal tissue a) Upper epidermis b) Lower epidermis 2. Mesophyll Tissue a) Palisade tissue b) Spongy tissue 3. Vascular Tissue a) Open collateral in dicot leaf b) Closed collateral in monocot leaf 45 In monocot root o The number of xylem arches is more than 12 In dicot root o The number of xylem arches is 2-5 In monocot stem o The ground tissue is not differentiated In dicot stem o The ground tissue is differentiated into cortex and pith In monocot leaf o The mesophyll tissue is not differentiated o Motor cell responsible for elasticity in movement In dicot leaf o The mesophyll tissue is differentiated into palisade tissue and spongy tissue 46 23  11/26/2023 Anatomy for plant organs 47 48 24  12/2/2023 Economic Botany Dr. Eman Tawfik Associate Professor of Genetics and Genetic Engineering Faculty of Science – Helwan University 1 Economic Botany Economic Botany is the interaction of people with plants. Economic botany deals mainly with how plants can be utilized to meet the financial and economic aspects of human life. This includes plant uses for food, feed, medicine, etc. Economic botany is the study of the relationship between people (individuals and cultures) and plants. 2 1  12/2/2023 What are the components of our breakfast? 3 What are important things we get from plants? Plants provide food in the form of fruits, As a product of photosynthesis, green plants vegetables, cereal grains, and seeds. provide oxygen. Plants are also used as building materials (timber), textiles (cotton, paper), medicine (aloe), biofuels (ethanol), and scents (perfumes). 4 2  12/2/2023 Types of plants II. Types of I. Classification plants according Based on to the Growth Habits composition of the seed IV. Types of III. Types of plants according plants according to their to the place of economic cultivation importance 5 I. Classification Based on Growth Habits If we consider plants, based on their height, some are too short while some are too tall to climb. Besides the height, stem thickness and delicacy also vary. Herbs Shrubs Trees Climbers Creepers 6 3  12/2/2023 7 II. Types of plants according to the composition of the seed Vascular plants: are Non-vascular plants: plants that use roots and plants that do not use stems to obtain their roots and stems to food. obtain their food. Seed plants: Plants that Seedless plants: Plants contain within their that do not contain fruits a seed through seeds inside their fruit. which they multiply. Angiosperms: the seeds Gymnosperms: Seeds are protected inside the grow without ovule, and are called protection, such as flowering plants. cones. 8 4  12/2/2023 9 III. Types of plants according to the place of cultivation Indoor plants: plants grown indoors, Outdoor plants: grown outside the and mostly ornamental plants home, in fields and farms. 10 5  12/2/2023 11 IV. Types of plants according to their economic importance CROPS VEGETABLES AND MEDICINAL AND DECORATION/ FRUITS AROMATIC PLANTS ORNAMENTAL PLANTS 12 6  12/2/2023 Crops A crop is a plant or plant product that can be grown and harvested for profit or subsistence. By use, crops fall into six categories: 1. food crops, 2. feed crops, 3. fiber crops, 4. oil crops, 5. ornamental crops, and 6. industrial crops 13 1) Feed Crops 2) Fiber Crops Feed crops, such as oats and Fiber crops, such as cotton and alfalfa, are harvested for livestock hemp, are harvested for textile and consumption. paper These crops contain nutrients that products. Textiles, or cloth, are animals need to develop. They are made from the dried and grown processed fibers of in agricultural fields but can also be certain plants. Most fibers used to found in natural meadows and make textiles are taken from the pastures. stem or roots of plants such as flax. Flax is used to make linen. 14 7  12/2/2023 Oil Crops Ornamental Crops Oil crops, such as canola and corn, are Ornamental crops, such as dogwood and harvested for consumption or industrial uses. azalea, are harvested for landscape Technologies developed in the past century gardening. Ornamental crops are most often have enabled crops to be processed and grown in nurseries, where they are purchased broken down into their primary components, for residential or commercial settings. including oil. Soybeans, for example, represented 61 percent of world oilseed production and 79 Ornamental crop production has deep percent of all edible oil consumed in the historical roots. The tulip crop of the United States in 2000. Netherlands, for example, has become a symbol of that country. Oil crops are harvested for use in cooking, such as olive oil and corn oil. Oil crops are also harvested for industrial use, such as oil paints, soaps, and lubrication for machinery. Fuel made from oil crops is called biofuel. 15 Industrial Crops Harvesting Crops Industrial crops, such as rubber and Methods for growing and harvesting tobacco, are harvested for their crops have developed over thousands products’ use in factories or of years. The earliest crops were machines. grown in Mesopotamia around 5500 B.C.E. Industrial crops include all crops used These crops, indigenous to an in the production of industrial goods, agriculturally rich area called the such as fiber and fuel products. Fertile Crescent, were grown near local sources of freshwater so they could be irrigated relatively easily. Wheat, barley, and figs were among the first crops. 16 8  12/2/2023 1. Corn 2. Soy Most Popular Crops 3. Hay 4. Wheat 5. Cotton 17 Popular cereals 18 9  12/2/2023 19 Vegetables and fruits 20 10  12/2/2023 What's the Difference Between Fruits and Vegetables? 21 22 11  12/2/2023 23 Ornamental plants Ornamental plants or garden plants are plants that are primarily grown for their beauty but also for qualities such as scent or how they shape physical space. Ornamental plants are grown for decoration, rather than food or raw materials. They are most often intentionally planted for aesthetic appeal. However, ornamental plants also serve some less obvious uses such as for fragrance, for attracting wildlife and for cleaning the air. 24 12  12/2/2023 25 Medicinal Plants What is a medicinal plant? A medicinal plant is any plant which, in one or more of its organs, contains substances that can be used for therapeutic purposes or which are precursors for the synthesis of useful drugs. Medicinal plants, also called medicinal herbs, have been discovered and used in traditional medicine practices since prehistoric times. 26 13  12/2/2023 Examples of medicinal plant 27 28 14  12/2/2023 What are aromatic plants? Aromatic plants are those that contain aromatic compounds – basically essential oils that are volatile at room temperature. What are the examples of aromatic plants? Aromatic plants, like perennial culinary herbs (rosemary and lavender) and many other plants, produce essential oils that are released when touching the foliage and flowers. Aromatic plants are rabbit and deer resistant because the aromatic oils are very bit 29 30 15  12/2/2023 Aromatic plants 31 What are Metabolites? Metabolites are the intermediate products produced during metabolism, catalyzed by various enzymes that occur naturally within cells. Eg., antibiotics, and pigments. The term metabolites are usually used for small molecules. The various functions of metabolites include; fuel, structure, signalling, catalytic activity, defence and interactions with other organisms. The metabolites are produced by plants, humans and microbes. 32 16  12/2/2023 Primary metabolites are compounds that Primary and are directly involved in the growth and development of a plant. secondary metabolites in secondary metabolites are compounds plants produced in other metabolic pathways that, although important, are not essential to the functioning of the plant. 33 What are primary plant metabolites? The decomposition products and the polymeric products formed during the process, are called primary metabolites, such as: 1. polysaccharides, 2. proteins, 3. nucleic acids, and 4. esters, 5. amino acids 6. enzyme or coenzyme 34 17  12/2/2023 These are the chemical compounds produced during the growth and development, processes. They are also involved in the Primary Metabolites primary metabolic processes of respiration and photosynthesis. The primary metabolites are formed in the growth phase. They maintain the physiological functions of the body and are known as central metabolites. They are the intermediate products of anabolic metabolism, which are used by the cells for the formation of essential macromolecules. Amino acids, vitamins, organic acids, are some of the primary metabolites produced industrially. Alcohol is the major primary metabolite produced on a large scale, industrially. 35 36 18  12/2/2023 Plant secondary metabolites can be classified into four major classes: What are the secondary 1.terpenoids, 2.phenolic compounds, metabolites in 3.alkaloids and 4.sulphur-containing compounds. plants? These phytochemicals can be antimicrobial, act as attractants/repellents, or as deterrents against herbivores. 37 Secondary Metabolites These compounds are produced by the organisms that are not required for primary metabolic processes. However, they can be important ecologically or otherwise. Secondary metabolites are considered to be the end products of primary metabolites because they are derived by the pathways in which the primary metabolites involve. For eg., antibiotics, toxins, pheromones, enzyme inhibitors, etc. Streptomycetes and related actinomycetes are the sources of novel secondary metabolites. 38 19  12/2/2023 39 40 20  12/2/2023 41 Primary Metabolites Secondary Metabolites Required for growth and Involved in ecological functions. maintenance of cellular function. Differences Occurs at the growth phase. Occurs at the stationary phase. between Produced in large amounts and Produced in small amounts and Primary and easy to extract. difficult to extract. Secondary metabolites Same in every species. Different in every species. Perform physiological functions in Derivatives of primary metabolites. the body. Eg., carbohydrates, vitamins, Eg., Phenolics, steroids, antibiotics, ethanol, lactic acid. pigments. 42 21  12/2/2023 43 Fruits and vegetables contain many vitamins and Vitamins minerals that are good for your health. Many of these are antioxidants, and may reduce the risk of and many diseases: vitamin A (beta-carotene) minerals in vitamin C vitamin E fruit and magnesium zinc vegetables phosphorous folic acid. 44 22  12/2/2023 Plant-Based Vitamins And Minerals Plants contain a complete spectrum of vitamins, minerals, aromatic oils, and phytonutrients that the human body can use. The vitamins and minerals extracted from plants come with other natural compounds, called co-nutrients, which work together with the vitamins and minerals to create beneficial processes in the body. Without these co-nutrients, some processes simply will not happen, rendering synthetic supplements useless. The benefits of certain vitamins and minerals are scientifically recognized by the health community. 45 46 23  12/2/2023 47 What are the example of plants containing vitamin? 48 24  12/2/2023 49 50 25  12/2/2023 Thanks a lot 51 26  12/9/2023 Plant Pathology Dr. Eman Tawfik Associate Professor of Genetics and Genetic Engineering Faculty of Science – Helwan University 1 Plant Pathology (Phytopathology) Plant pathology is a science that studies plant diseases and attempts to improve the chances for survival of plants when they are faced with unfavorable environmental conditions and parasitic microorganisms that cause disease. Plant pathology is the study of plants and their pathogens, the process of disease, and how plant health and disease are influenced by factors such as the weather, nonpathogenic microorganisms, and plant nutrition. It encompasses fundamental biology as well as applied agricultural sciences. 2 1  12/9/2023 The study of plant 1) causes, diseases is called plant pathology. 2) mechanisms by which What is the Plant Pathology is the diseases occur, meaning of plant study of plant diseases including: pathology? 3) interactions between plants and disease- causing agents, and 4) controlling diseases. 3 Pathogen & Host Organisms that cause infectious disease include fungi, oomycetes, bacteria, viruses, viroids, virus-like organisms, phytoplasmas, protozoa, nematodes and parasitic plants. Living organisms that attack and obtain their nutrition from the plant they infect. The parasitic organism that causes a disease is a pathogen. The plant invaded by the pathogen and serving as its food source is referred to as a host. 4 2  12/9/2023 What causes plant disease? Infectious plant diseases are caused by living organisms that attack and obtain their nutrition from the plant they infect. The parasitic organism that causes a disease is a pathogen. Numerous fungi, bacteria, viruses, and nematodes are pathogens of corn and soybean in Iowa. 5 What is the Disease Triangle? The disease triangle (or pyramid) is a classical concept in plant pathology and helps us to understand some elements must exist before a plant disease can occur. A soybean disease will only occur if a susceptible PLANT HOST, a PATHOGEN, and a favorable ENVIRONMENT are present in that field. Some plant pathologists will also add TIME as a fourth factor and then call it a pyramid. 6 3  12/9/2023 7 PLANT HOST Different soybean varieties can vary in their susceptibility to a Some pathogens may even be A susceptible PLANT HOST, in specific pathogen, so check seed able to infect a resistant variety, our case, is a soybean plant that catalogs and talk to your seed but this will result in little to no can be infected and sustain a dealer if you are trying to yield loss when compared to an pathogen. manage a particular disease in infection of a susceptible line. your area. For example, corn is a non-host of the soybean cyst nematode Crop rotation can also be (SCN) and frogeye leaf spot; important in this context. therefore, corn can a good non- host crop to rotate with soybeans. 8 4  12/9/2023 PATHOGEN A PATHOGEN is a disease-causing microorganism (bacteria, fungi, or nematode). A soybean disease can only occur if that specific pathogen is present. Some management practices can reduce pathogen populations in a field, while other pathogens can move through the wind; therefore management practices may be less effective. 9 ENVIRONMENT Soybean diseases may be The response of some diseases The ENVIRONMENT refers to influenced by temperature, to weather helps to explain why weather and local climate humidity, soil compaction, we observe more yield losses variables. moisture level, texture, PH, and caused by certain diseases in so on. some years. The drought also made the For example, the disease symptoms of nematodes and pressure of soybean foliar other soil-borne diseases more pathogens (ex.: frogeye leaf evident later in the season since spot) was particularly low during a weakened root system can not the 2022 season due to the low withstand dry conditions very moisture in the air. well. 10