Plant Structure and Growth

PLANT STRUCTURE AND GROWTH

• Plants require dilute/dispersed resources like carbon dioxide and soil nutrients
• Plants are immobile; therefore, the diffusion of nutrients from the environment limits plant growth

Dendritic Form

• Branching growth helps diffusion by exploring a large volume of space
• Thick cell walls in plants help them stand
• Cell walls surrounding water-inflated cells provide good building material
• Thick, lignified cell walls, as found in wood, are self-supporting
• Vacuoles in plant cells take up water and occupy a large volume without diluting cytoplasmic contents
• Vacuoles occupy 95% of the cell's volume and can be loosened when young

Plant Organs

• Plant bodies contain organs grouped into organ systems
• Organs consist of several types of tissues that cooperate for a specific function
• Plants obtain resources from two different environments: water/minerals from the ground via subterranean roots and CO2/light from above ground via aerial shoots include stems and leaves
• Roots and shoots depend on each other to survive
• Roots lack chloroplasts and rely on nutrients transported from leaves/stems
• Shoots rely on water and minerals absorbed by roots from the soil

Root

• Anchors the plant in soil, absorbs/transports minerals/water and stores carbohydrates
• All roots form the root system
• Root hairs, which are finger-like projections near the tip, increase the root's surface area and are outgrowths of the root epidermal cells
• Roots need oxygen to survive and will suffocate in water, while some are green and photosynthetic

The Shoot System

• Is made up of stems, leaves, and structures for reproduction like flowers
• Stems bear leaves and buds and are generally above ground
• Stems support and separate leaves for photosynthesis and flowers for reproduction

Stem Nodes and Internodes

• Nodes are the points where leaves are attached
• Internodes are the portions of stem between nodes

Leaves

• Are the main photosynthetic organs in most plants, with green stems also performing photosynthesis
• Most leaves consist of a petiole with a flattened blade that joins the leaf to a node
• Leaves can be modified for different functions, like pea tendrils for support or onion leaves for storage
• Plants can have modified roots, stems, and leaves like rhizomes, potatoes, and onions and horizontal stems

Plant Development

• Continues as long as conditions are favorable and new modules are added indefinitely
• Is described as plastic can be "molded", and they respond to growth more rapidly than animals
• Plant's body or form depends on its experience
• Flag trees have suppressed growth on stressful windward sides
• Fragile, short-lived organs are regularly replaced, such as a tree shedding leaves before extensive damage
• Tissue systems are one or more tissues organized into a functional unit within the plant

Plant Tissue Systems

• Each plant is composed of three: vascular, ground, and dermal
• The vascular tissue system supports and transports between the root and shoot systems
• Xylem tissue conveys water and dissolved minerals upward from roots
• Tracheid and vessel elements have lignified secondary walls are dead at maturity and conduct water
• Fibers have lignified secondary walls
• Phloem tissue transports sugars/other organic nutrients from leaves/storage tissues while roots form a central cylinder

The Ground Tissue System

• Functions in photosynthesis, storage, and support
• Most of a young plant is ground tissue, which fills the space between the epidermis and vascular tissue system
• Pith is ground tissue internal to vascular tissue, while cortex is ground tissue external to vascular tissue

Dermal Tissue System

• Provides an outer protective covering
• It is the first line of defense against physical damage and infectious organisms
• Nonwoody plants have a single layer of tightly packed cells called the epidermis
• Dermal cells secrete cuticle, a waxy coating, to prevent water loss on leaves and most stems

Growing Points of Plants

• Display cheap growth, and can easily grow by absorbing water
• Root and shoot apical meristems lead to primary growth along the plant axis
• Tiny apex cells consist of nuclei mainly
• Axillary bud meristems turn into branches, follow the same growth mechanism, and are the origin of shoot system branches
• Axillary bud meristems remain dormant until receiving a stimulus for growth

Plant Nodes and Roots

• Nodes are points on the stem where leaves, branches, or reproductive structures develop
• Root cap absorbs the stress of cells pushing through the soil and protects root apical meristem
• Lateral roots originate in the outer layer of the vascular cylinder, the pericycle, and burst through the epidermis of the root, connecting to the vascular cylinders of branched roots

Lateral Meristems

• Root and shoot lateral meristems lead to secondary growth
• This growth is in width and is perpendicular to the plant axis
• Shoot lateral meristems are vascular cambium, which helps stems get wider, epidermis cracks, and is shed

Vascular Cambium

• Arranged in a ring around the central pith
• One layer of cells that divides and produces descending cells in the horizontal plane
• Tree rings are growth increments where first cells are produced in spring with more water and are bigger
• As water becomes less available during the growing season, cells will be smaller and darker
• When conditions become unfavorable in winter, cell division ceases and can be used to determine historical climate and growing conditions
• Tree ring index or dendrochronology is the science of dating tree rings to determine the year they were formed
• Cork cambium produces cork cells for the outside, cells that have lost their cytoplasmic content, and are protective since nothing can feed on the cork

Plant Seed Germination

• Plant resumes growth and development that was suspended in seed dormancy
• The plant embryo lies dormant in the seed and is protected from the elements, and broken by water or warm temperatures after an extended cold period
• Lettuce seeds use phytochromes to detect light before they germinate and will germinate in response to continuous white light (or red light) or a one-minute flash of white/red light
• If a seed receives red wavelengths, it will initiate the conversion of Pr to Pfr and are surrounded by a supply of food
• Seeds of many plant species have a period of dormancy and will not germinate, even when exposed to water

Plant Seedling Growth

• Some seedlings grow taller in shady areas, attempting to get more light, and light is enriched for far red wavelengths, causing phytochrome conversion of seedlings to Pr inactive forms
• Germination begins when the seed takes up water and bursts the seed coat

Shoot and Root Balance

• Plants must decide how to balance their root and shoot systems
• The plant partitions carbon resources to advantage its reproduction/nutrient uptake, if there is too much root, there isnt enough for reproduction and if there is too little root then the shoot might dry out and die
• Auxin (IAA) travels down the plant from the site of synthesis in shoot apexes and encourages growth of root branches
• Cytokinin travels up the plant from its site of synthesis in root apexes and promotes lateral branch formation in the shoot system, balancing the auxin and cytokinin

Plant Nutrition and Transport

• Plants have two separate transport systems that require a constant supply of water and dissolved minerals from soil
• Xylem sap is a solution of water and inorganic nutrients that flows from roots through the shoot system and leaves
• Water molecules are joined through cohesion in xylem cell walls

Transpiration

• Water pressure gradient: Transpiration is unavoidable when stomata are open to absorb CO2, but this also allows the exit of water
• In transpiration photosynthesis compromise, plants lose 100 molecules of water for every CO2 fixed
• Minerals are transported up the xylem column to aerial parts of the plant and provides evaporative cooling

Pholem and Xylem Transport Compared

• Pholem transports products of photosynthesis from where they are made/stored to where they are needed
• Sieve-tube elements are food-conducting cells arranged end to end in long tubes, but no absolute flow direction
• Pholem sap contains inorganic ions, amino acids, and hormones and its main solute is usually sugar transported by phloem loading

Plant Contol Systems

• Tropism is any growth response that results in plant organs curving toward or away stimuli
• Positive phototropism is the bending process towards light.
• Bodily responses are controlled by hormones in plants
• IAA is causes cell elongation by acidifying cell walls on the non-illuminated side which is acid growth hypothesis
• Makes cell walls stretchier and more extensible

Plant Gravitropism

• A plant or root bending in response to gravity
• Positive gravitropism > bending toward pull of gravity
• Negative gravitropism > bending away from pull of gravity
• Starch grains in root cells might be gravity sensing structures
• Thigmotropism is directional growth response stimulated by touch like tendrils on climbing plants

Plant Flowering

• Flowering of many plants in temperate latitudes is sensitive to season
• Short day plants flower when photoperiod falls below a critical value and plant germinate, seedling grows, becomes mature enough in June
• Long day plants are induced to flower when the night period falls below a critical value, shorter than a day

Plant Phytochrome

• Phytochrome is involved in the perception of day length
• Plant hormones produced in very low concentrations can have a profound effect on growth and development
• Hormones affect division, elongation, and differentiation of cells
• Auxins stimulate stem elongation, affect root growth, differentiation, branching, the development of fruit, apical dominance, phototropism and gravotropism and retard leaf abscission
• Cytokinins affects root growth and differentiation and stimulate cell division and growth
• Gibberellins Promote bud development, stem elongation and leaf growth, stimulate flowering, fruit development and seed germination
• Abscisic acid (ABA) Inhibits growth, closes stomata during dry spells, helps maintain seed dormancy and promotes leaf aging
• Ethylene Promotes fruit ripening and leaf abscission, opposes some auxin effects and promotes root formation and flowers in some species

Plant Auxin

• Moves in only one direction, from shoot tips toward base, diffuses from cell to cell
• Binds to receptors in cells, creates a signal that stimulates growth by causing cells to elongate
• Auxin stimulates proteins within the plasma membrane to pump protons into the cell wall, and lowers pH and also induces cell division in vascular cambium, promotes growth in stem diameter

ANIMAL PHYSIOLOGY

• Structural hierarchy includes cellular, tissue, organ and organism levels

Animal Tissues

• Integrated groups of similar cells that perform a common function that are specialized
• Epithelial tissue is sheets of closely packed cells for body surface covering or internal organ/cavity lining
• Connective tissues include fat, osseous, blood, and cartilage
• Muscle tissue is abundant and can either be cardiac or smooth
• Cardiac is striated and smooth is not

Multi Tissue Function

• Organs perform a specific task and contain nervous, epithelial, connective, and muscle tissues
• Organ systems are multiple organs functioning under one system

Animals and Environments

• Animals have specialized exchange surfaces that allow them to exchange materials with the environment (respiratory, digestive, excretory, integumentary)
• A branched folded surface gives a efficient exchange environment
• External surfaces are internal in complex animals which protects from damage/dryness

Homeostasis

• Claude Bernard founded the observation and practice of homeostasis
• Maintains a relatively stable internal environment despite changing external conditions
• Many homeostatic control centers are located in the brain and hypothalamus and regulation of oxygen to the tissues is a prime example

Feedback Loops

• Response to stimulus reduces stimulus as common form of feedback loop
• Positive feedback: Response to stimulus increases the stimulus which is less common

NERVOUS SYSTEM

• Provides quick communication and Input from sensory receptors travels very quickly to CNS
• Motor information travels efferently to effector

Neurons and Glial Cells

• Neurons conduct nervous signals, while glial cells perform support functions

Transmission Across Neurons

• Membrane potential is the separation of charges across a membrane Separation of charges across a membrane
• Electrochemical gradient involves the Gradient for ion that takes electrical environment (membrane potential) and concentration of ion into account
• Action potential: Signal being transmitted along a neuron arises from membrane depolarization exceeds electrical gradient, includes a resting state, depolarization, repolarization, and undershoot

Synapses

• The junction point between neurons which involves a chemical diffusing from a receiving cells
• One postsynaptic cell can synapse with multiple presynaptic cells and includes Excitatory and Inhibitory postsynaptic potentials

CIRCULATION

• Mammalian heart as four chambers which drive two circuits of blood flow: Pulmonary and Systemic
• Atria receive blood from circulation, ventricles pump blood to circuits

Blood Vessels

• The artery carries blood away from the heart, while the vein brings blood to the heart
• Smaller vessels like the arterioles of the artery and the venules of the veins

Cardiac Cycle

• Inherent activity of heart due to pacemaker that is influenced/modified by other factors
• Systole is caused by atria contraction and AV valves are closed
• Diastole is passive filling of ventricles
• Sinoatrial node is the Heart's natural pacemaker that cells can initiate atrial systole

Composition of Blood

• Cellular elements that come from stem cells of bone marrow which is erythocytes, leukocytes and platelets
• Plasma is blood without cells and is composed of Proteins Nutrients, Ions, Wastes and Hormones

Blood Volume

• The normal value is 45% and regulated, departures are either adaptive or pathological(Anemia or Polycythemia)
• Blood volume is Adaptive when there is a Response to oxygen deprivation

Red Blood Cells

• Cellular elements originate from stem marrow, that which is constantly mitosis
• Biconcave discs that have a higher surface/volume ration than sphere with Hemoglobin: are which consists of proteins
• Oxygen solubility in blood is due to hemoglobin

Erythropoiesis and Blood Doping

• Takes ~4 days and Normally balanced with erythrocyte destruction
• Blood doping is synthetic EPO used to stimulate the production of RBCS, its detection as to do it its glycogen profile

Blood Pressure and Hemolysis

• Breakage in capillaries is due to mechanical stress
• Hemolysis of broken RBC’s done by macrophage
• Can live without spleen > overactive destruction of RBC

Binding to Blood

• Oxygen binding to hemoglobin is cooperative and the conformational changes in hemoglobin
• Hemoglobin with carbon dioxide lowers for oxygen which cause the Bohr effect and hydrogen ions
• Has high retention less oxygen at lower , higher carbon dioxide concentration and involves Bisphophoglycerate (BPG)

Internal and External Respiration

• Oxygen diffuses down pressure gradient from the Alveolar to the pulmonary(internal) and from the systemic capillaries (external)
• Carbon dioxide diffuses down partial pressure gradient from the system capillaries and to the lungs via diffusion
• There is higher fetal to give fetus better oxygen absorptioin

Blood Control Responses

• Have a lot oof blood, store some in spleen and Have a lot oof blood, store some in spleen Muscle is myoglobin
• Diving response includes HR slowdown
• Vasoconstriction that bodies are the sacrificing oxygen needs of periphery to serve core

Blood Loss Protection

• Stopped by a Platelet plugs small fragmented pieces of cells and fibrin formation
• Platelets are important for clotting and forming and don't respond to smooth blood

Blood Cascade

• Proteins activated multiple factors
• Opposing clotting is smooth blood vessels and anti-blood clotting such as warafin
• Favoring clotting is is by rough blood vessels
• Fibrinolysis: Clot dissolution due tissue plasmin activator

DEFENSE SYSTEMS

• Pathogens elicit defense responses(Bacteria, Fungi Protozoa Viruses and Worms)

Innate Immunity

• Is not keyed to individual pathogens Do not adapt to specific pathogens
• This includes Barriers like the skin or the physical properties of mucos
• Phagocytes that are eat tissue invaders and Recognize enemies by direct interaction with molecules produced on surface of target while also recognizing their potential with lables

Natural Killers

• Can attack tumor/viral vessels releasing granules
• Cytokines: Proteins secreted by immune system cells that regulate activities of nearby cells Can induce anti-viral defenses in target cells

30 serum proteins

• Can destroy the membrane of foreign cell
• Opsonize an invader, attract macrophages
• Inflammation Response to tissue damage

Fever

• Body's thermostat is reset upwards after an infection
• Higher temperature inhibits growth of pathogen Speeds up action of defensive cells

Adaptive immunity

• Are keyed to individual pathogens with populations cells to target
• Each defensive molecule interacts with a specific molecular configuration
• Antibodies recognizes antigens that are encoded in its immunoglobulins