Plant Root Systems PDF

# The "Typical" Plant Body ## The Root System - Underground (usually) - Anchor the plant in the soil - Absorb water and nutrients - Conduct water and nutrients - Food Storage ## Above ground - Elevates the plant above the soil - Many functions including: # Tap root system * It develops from ra...

# The "Typical" Plant Body ## The Root System - Underground (usually) - Anchor the plant in the soil - Absorb water and nutrients - Conduct water and nutrients - Food Storage ## Above ground - Elevates the plant above the soil - Many functions including: # Tap root system * It develops from radicle of the embryo (the primary root is the first organ to appear when a seed germinates downward into the soil, anchoring the seedling). * It has a persistent primary root known as tap root. * The system grows deep into the soil. * There is one main root called taproot and it produces laterals called secondary and so on. # Tap root system * Taproot is the main thick root or the primary root of the root system of dicotyledonous plants. * Taproot is thick and grows deeper into the soil vertically. * Hence, dicot plants can withstand drought conditions well compared to the monocot plants. * From the taproot, secondary, tertiary roots and lateral roots develop through the soil to absorb water and nutrients. # Normal Tap root - Morphology of the root - Normal tap root - Lateral roots - Main root - Root tip - e.g. *Ricinus* sp. ## Storage Tap Roots ### A) Fusiform - Fusiform is a modified tap root. - The primary root of the system is swollen at the middle and tapers gradually at both the ends forming a spindle shaped structure. - e.g. *Raphanus sativus* (Radish) ### B) Conical - In the conical form of root modification the roots are swollen and are broad at the base, the apex part gradually tapers forming a con like structure like in carrot. - e.g. *Daucus carrota* (Carrot) ### C) Napiform - The base region of the root is swollen becoming almost spherical in shape, and then it abruptly tapers towards the lower end, forming a tail-like structure. - Example of Napiform roots are turnip. - e.g. *Brassica rapa* (Turnip) # Adventitious root - The adventitious root system, also known as the fibrous root system, is one of the two main types of root systems. - The root system has numerous hair-like roots growing near the surface of the soil. - Unlike a taproot system, it does not have a thick primary root. Hence, adventitious roots are all alike. - The adventitious root system is present in monocot plants. These roots develop from the stem, leaves and other parts other than the radicle. - Moreover, adventitious roots are short-lived. Some adventitious roots are aerial. # Taproot vs Adventitious Root | | Taproot | Adventitious Root | |---|---|---| | Definition | Taproot is the primary thick single root of the root system of dicotyledonous plants | Adventitious roots are the small thin hair-like roots of the root system of monocot plants | | Bearing Plants | Most flowering plants, shrubs and trees | Grasses | | In the Soil | Travel deep into the soil | Grow near the surface of the soil | | Origin | Develops from the radicle | Develop from the stem, leaves or other parts of the plant other than the radicle | | Lifetime | Persistent | Short time | | Number of Roots Per Plant | Only one taproot is present | There are numerous adventitious roots per plant | | Lifetime | Normally a thick root | Thin and hair-like | | Differentiation | Taproot is the main root while secondary, tertiary and rootlets are present in the taproot system | There is no such differentiation of the roots. All roots are small, thin and hair like | | Surviving in Drought | Plants that have a taproot system can survive in drought areas | Plants that have an adventitious root system cannot survive in drought conditions | | Venation Pattern of the Leaves | Plants that have a taproot system show reticulate venation in leaves | Plants that have an adventitious root system show parallel venation in leaves | # Adventitious root - It develops from part of the plant other than the radicle. - Primary root is short lived. - The adventitious roots do not grow deep into the soil. - A number of main roots develop at one spot. All roots are similar thickness except in certain cases where they are swollen for storage. # Modification of Adventitious roots - The root system may be changed to different forms for special functions like storage, mechanical support and vital functions. ## Prop - They are adventitious roots that form from stem tissue. Prop roots main function is for structural stability for the stem. - e.g. *Zea mays* ## Climbing ## Aerial ## Tuberous - The adventitious roots in this are grown from the nodes of the running stem. These roots are modified are swollen into irregular forms and are known as tuberous roots ex: sweet potato. ## Fibrous # Fibrous Roots - Generally thin, somewhat hair-like, and numerous. - Better able to hold within soil, giving plant better stability - Fibrous roots dry out quickly # Aerial roots - Roots above the ground. - They are almost always adventitious - They can absorb water from the air. - They are also used to hold on to the support. - Ex : vine plant - e.g. *Anthurium* sp. # Climbing roots - These roots help the plant in climbing by penetrating the cracks and stick firmly to support. - e.g. *Hedera* # What is tissue? - A group of cells along with intercellular substances that perform a specific function is called tissue. - There are mainly four different types of tissues present in our body. 1. Epithelial: Provides covering or lining 2. Muscular: Helps in movement 3. Neural: Responds to stimuli 4. Connective: Supports, links and cushions # What is tissue? - Two or more cells of the same type performing a common function - Four types of tissue - Epithelial - Connective - Muscular - Nervous # Introduction - Each animal cell is specialized to emphasize certain activities, although most continue to carry on basic functions such as cellular respiration. - Groups of similarly specialized cells along with any extracellular material, associate together to form tissues. - Different subtypes from each of the four basic tissue types are combined to make the body's organs. - Groups of related organs are strung together functionally, and usually structurally, to form systems. Taken together and arranged correctly, systems form the entire body. # Animal organism - Systems (e.g., digestive, respiratory) - Organs (e.g., esophagus, stomach, trachea, lungs) - Epithelial, connective, muscular, and nervous tissues - Specialized cells - Organelles # Four types of tissue - Epithelium - Connective tissue - Muscle tissue - Nervous tissue # Epithelium - Cell membrane - Nucleus - Cytoplasm - Cilia - Microvilli - Simple squamous - Simple columnar - Stratified squamous - Stratified columnar - Simple cuboidal - Stereocilia - Stratified cuboidal - Transitional - Pseudostratified columnar - Cleveland Clinic ©2021 # Types of epithelia - An epithelium is a layer of cells that covers a surface or lines a cavity. - The epithelium in a continuous, thin and protective layer of cells that are densely packed with some intercellular matrix. - These cells are present on the surfaces of the body serving as a protective barrier. # Classification of epithelia is based upon 2 criteria: 1. Number of cell layers 2. Shape of epithelial cells # According to the number of layers of epithelial cells - Simple: 1 layer of epithelial cells - Epithelial Tissue - Pseudostratified: Simple but appear stratified - Stratified: More than 1 layer of epithelial cells # According to the shape of epithelial cells - Epithelial Tissue - Squamous: Wide, thin cells - Cuboidal: Cube-shape cells - Columnar: Elongated cells # Simple Columnar Epithelium # Simple Squamous Epithelium # Simple Cuboidal Epithelium # Connective Tissues - Derive from embryonic mesoderm - Divided into two major classes - Connective tissue proper: - Loose or dense - Special connective tissue: - Cartilage, bone and blood - All have abundant extracellular material called the matrix - Protein fibers plus ground substance - Ground substance is fluid material containing an array of proteins and polysaccharides # What is Connective Tissue? - Connective tissues, as the name implies, support and connect different tissues and organs of the body. They are widely distributed in every part of the body. - They originate from the mesoderm (the middle germinal layer of the embryo). - Connective tissue is made up of a few cells present in the intercellular framework of protein fibers secreted by the cells, known as collagen or elastin. - The cells also secrete a thin gel of polysaccharides, which together with fibers make matrix or ground substance. # Types of Connective Tissue - The classification of connective tissue is as follows: 1. Loose Connective Tissue 2. Dense Connective Tissue 3. Specialized Connective Tissue # Loose Connective Tissue - Loose connective tissues are present all over the body, where support and elasticity both are needed. - Blood vessels, nerves and muscles, all have a loose connective tissue wrapping. They form the subcutaneous layer under the skin along with adipose tissues, attaching muscles and other structures to the skin. - The fibers and cells are loosely arranged in the semi-fluid matrix. - They are found between many organs as a filling and act as a shock absorber and reservoir for salt and fluid. # Adipose Tissue - They are present under the skin and store fat. It acts as a shock absorber and helps in maintaining body temperature in colder environments. # Connective Tissue Proper - **Dense connective tissue:** - In the dense connective tissue, fibroblast cells and fibres are compactly packed. - Their main function is to support and transmit mechanical forces. - They are somewhat less flexible than loose connective tissue. On the basis of the arrangement of collagen fibers, they are divided into two types: ### Dense regular tissue - In the dense regular connective tissue, the orientation of fibers are regular. - The collagen fibers are present between the parallel running bundles of fibers. The regular arrangement enhances tensile strength and poses resistance to stretching in the direction of the orientation of fiber. Examples of dense regular tissue are tendons and ligaments. # Special Connective Tissue - Cartilage is mostly present in the embryonic stages and works as a supporting skeleton. - Most of the cartilage is replaced by bones in adults, however, it supports some structures in adults too. - In humans, cartilage is present between the bones of the vertebral column, in the external ear, nose and hands. - The cartilage consists of chondrocytes cells, which are enclosed in a hard, rubbery matrix, secreted by them. They secrete collagen fibers also, which provide additional strength. - Chondrocytes lie in the cavities known as lacunae, in a group of 2-4 cells or singly. - Cartilage possesses elasticity, but is firm too. - They lack nerves, blood and lymph vessels. # Connective Tissue Proper * **Tendons and Ligaments:** Tendons attach bones to skeletal muscles. Ligaments attach two bones together. * **Dense irregular tissue:** There are many fibers including collagen, which are oriented irregularly or randomly. The irregular arrangement gives uniform strength in all directions. Fibers may form a mesh-like network. This type of tissue is present in the dermis of the skin. ## Special Connective Tissue - Bone is the hardest connective tissue and helps in maintaining the shape and posture of the body, it protects internal organs. They are rich in collagen fibers and calcium, which give strength. - The cells of the bone are known as osteocytes. They are present in lacunae and secrete the matrix. There is substantial blood supply in bony tissues. # Blood - Blood is made up of various cells present in the plasma. - The blood contains red blood cells (RBCs), white blood cells (WBCs) and platelets. - RBCs have haemoglobin and transport oxygen. - WBCs form a defence system and protect from foreign antigens. - Platelets are important for blood clotting. - Plasma contains proteins, water, hormones, salts, etc. to transport to different parts of the body. # Muscular tissue - Muscles are classified into three types: ## Smooth - Unstriated muscles - Central nucleus - e.g. wall of digestive, respiratory & urogenital tracts ## Skeletal - Striated - Linear and cylindrical - Multinucleated (peripheral) - e.g. voluntary muscles ## Cardiac - Striated - Branched, intercalated disc - Central nucleus - e.g. heart muscle # Muscular tissue - A muscle is composed of elongated cells called “muscle fibers" which transform chemically stored energy into mechanical work. - Rich in Blood vessels & nerves in the associated connective tissue - Muscle fiber is surrounded by basal lamina; its plasma membrane is called sarcolemma & its cytoplasm is called sarcoplasm. # Nervous tissue - Nervous tissue is found in the brain, spinal cord, and nerves. - It is responsible for coordinating and controlling many body activities. - It stimulates muscle contraction, creates an awareness of the environment, and plays a major role in emotions, memory, and reasoning. - To do all these things, cells in nervous tissue need to be able to communicate with each other by way of electrical nerve impulses. - The cells in nervous tissue that generate and conduct impulses are called neurons or nerve cells. - These cells have three principal parts: the dendrites, the cell body, and one axon. # Nerve Tissue - Cells include neurons and their supporting cells called neuroglia - Most neurons consist of three parts - Cell body: Contains the nucleus - Dendrites: Highly branched extensions - Conduct electrical impulses toward the cell body - Axon: Single cytoplasmic extension - Conducts impulses away from cell body # Nervous tissue - Dendrites are extensions, or processes, of the cytoplasm that carry impulses to the cell body. - An extension or process called an axon carries impulses away from the cell body. - Nervous tissue also includes cells that do not transmit impulses, but instead support the activities of the neurons. - These are the glial cells (neuroglial cells), together termed the neuroglia. - Supporting, or glia, cells bind neurons together and insulate the neurons. Some are phagocytic and protect against bacterial invasion, while others provide nutrients by binding blood vessels to the neurons. # Structure of a Typical Neuron - Dendrites - Axon Terminals - Nucleus - Node of Ranvier - Schwann's Cells - Axon - Myelin Sheath - Cell Body # Neuroglia do not conduct electrical impulses - Support and insulate neurons and eliminate foreign materials in and around neurons - Associate with axon to form an insulating cover called the myelin sheath - Gaps, known as nodes of Ranvier, are involved in acceleration of impulses # Main features | Location | Type of cells | Histology |---|---|---|---| | **Skeletal muscle** | Fibers: Striated, tubular and multi nucleated - Voluntary - Usually attached to skeleton | | | | **Smooth muscle** | Fibers: non-striated, spindle-shaped, and uninucleated. - Involuntary - Usually covering wall of internal organs. | | | | **Cardiac muscle** | Fibers: striated, branched and uninucleated. - Involuntary - Only covering walls of the heart. | | | # Nervous tissue - Nervous tissue is found in the brain, spinal cord, and nerves. - It is responsible for coordinating and controlling many body activities. - It stimulates muscle contraction, creates an awareness of the environment, and plays a major role in emotions, memory, and reasoning. - To do all these things, cells in nervous tissue need to be able to communicate with each other by way of electrical nerve impulses. - The cells in nervous tissue that generate and conduct impulses are called neurons or nerve cells. - These cells have three principal parts: the dendrites, the cell body, and one axon. # Nerve Tissue - Cells include neurons and their supporting cells called neuroglia - Most neurons consist of three parts - Cell body: Contains the nucleus - Dendrites: Highly branched extensions - Conduct electrical impulses toward the cell body - Axon: Single cytoplasmic extension - Conducts impulses away from cell body # Nervous tissue - Dendrites are extensions, or processes, of the cytoplasm that carry impulses to the cell body. - An extension or process called an axon carries impulses away from the cell body. - Nervous tissue also includes cells that do not transmit impulses, but instead support the activities of the neurons. - These are the glial cells (neuroglial cells), together termed the neuroglia. - Supporting, or glia, cells bind neurons together and insulate the neurons. Some are phagocytic and protect against bacterial invasion, while others provide nutrients by binding blood vessels to the neurons. # Structure of a Typical Neuron - Dendrites - Axon Terminals - Nucleus - Node of Ranvier - Schwann's Cells - Axon - Myelin Sheath - Cell Body # Neuroglia do not conduct electrical impulses - Support and insulate neurons and eliminate foreign materials in and around neurons - Associate with axon to form an insulating cover called the myelin sheath - Gaps, known as nodes of Ranvier, are involved in acceleration of impulses