Introduction to crop physiology
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The document is an introductory overview of crop physiology, explaining the definition and importance of plant physiology, including aspects like metabolism, growth, and responses to environmental factors. It discusses the cellular structure and functions, including details about organelles like chloroplasts, mitochondria, and the cytoskeleton, highlighting their roles in plant life processes. The content emphasizes practical applications in agriculture for enhancing crop yield through understanding plant functions and physiology.
Introduction to crop physiology
- 1. INTRODUCTORY CROP PHYSIOLOGY Compiled by : Subodh Khanal Asst Professor Gauradaha Agriculture Campus, Jhapa Email Address: Subodh.agroecology@gmail.com Phone : 9851138999
- 2. What is crop/plant physiology •Greek: physis=nature, logus=study so means “ discourse of nature of plants” •Definition: Science of how plants develop, grow and respond to their environment at cellular and biochemical level Julius von Sachs (October 2, 1832 - May 29, 1897) is considered as the father of Plant Physiology
- 3. So, • Plant physiology is the study of The functions occurring in plants The vital processes occurring in plants How plant works • In essence, plant/crop physiology is the study of plant way of life which include various aspects of plant life and survival Metabolism Water relation Mineral nutrition, development Movement, growth and transport process
- 4. What will you be studying? • Physical aspects: biophysical phenomenon, soil water relation, absorption and translocation of water, transpiration, ascent of sap, guttation e.t.c. • Metabolic aspects: photosynthesis,respiration, translocation of photosynthates • Growth and development aspects: seed dormancy, vernalization, photoperiodism, seed germination, growth and development,growth hormones, flowering, senescence.
- 5. Importance/ practical application • Understanding the physiological aspects of seed germination, seedling growth, crop establishment, vegetative development,flowering, fruit and seed setting and crop maturity, plant hormone interaction, nutrientphysiology,stress (biotic/abiotic) physiology etc., provides a reasonable scientific base for effective monitoring and beneficial manipulation of these phenomenon’s. • Since in agriculture we are interested in economic yield which is the output of these phenomenons and well beingness of plants, Plant Physiologyprovides a platform for getting better yield of crops.
- 6. Dealt under following areas: •Seed physiology: seed is the basic unit of agriculture, ways of enhancing germination and breaking dormancy •By knowing the different inputs requirement of plants (water, nutrients, sunlight) we can easily manage the plant population to get highest yield. •Growth measurement of crops; pruning of fruits is done principle of proper canopy management for better photosynthesis. •Increase HI: . Example: excessive vegetative growth period in Ground nut produces less number of Pods as the reproductive period gets constricted. Thus less economic yield
- 7. • Modeof action of differentweedicides: interruptingphotosynthetic electron flow (Ex. Paraquat, diuron)or electron flow of respiration. • Nutriophysiologyis yet another importantarea to under stand crop physiology. It helped in identification of essential nutrients,ion uptakemechanisms,their deficiency symptomsand corrective measures.It also helps to check the toxicity symptomsof various nutrients. • Responseof plant to the relative length of day and night is called as photoperiodism.Thisconceptwas used to choosephoto insensitive varieties and off season cultivation. • The regulation of flowering,seed formation and fruit setting has been controlled throughthe application of differenthormones • Soil fertility is maintained through BNF. • Post harvestmanagement • Managementof biotic and abiotic stress • Production of secondary metabolites • Fortification (Posilo Makai 1, Zinc gahun 1 , zinc gahun 2
- 8. CELL PHYSIOLOGY •The cell (from Latin cella, meaning "small room") is the basic structural, functional, and biological unit of all known living organisms. •Cells are often called the "building blocks of life". The study of cells is called cell biology. •The cell was discovered by Robert Hooke in 1665, who named the biological units for their resemblance to cells inhabited by Christian monks in a monastery.
- 9. •Cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that All organisms are made up of one or more cells and the products of those cells. All cells carry out life activities (require energy, grow, have a limited size). New cells arise only from other living cells by the process of cell division
- 10. Ultra structure of cell • The ultrastructure of a cell is its fine structure as revealed at high magnification. • Organisms made of a single cell, such as bacteria and the fungus yeast, are described as being unicellular. • Organisms made of many cells such as animals, most plants and many species of fungi, are described as being multicellular. • The cell exists in two forms: 1. Eukaryotic cell, which has a nucleus that is enclosed in a nuclear envelope and several membrane- limited compartments e.g. the human cell. 2. Prokaryotic cell which has no nucleus and is devoid of membrane-limited compartments e.g. the bacterial cell. • Animal, fungal and plant cells all contain structures specialised for particular functions called organelles.
- 13. Cell wall •Cell wall is a non-living component of the cell and is secreted and maintained by the living portion of the cell, called protoplasm. •A typical cell wall is composed of three different regions Middle Lamella: ca and mg pectate (long chain of poly galacturunic acid) Primary cell wall (1-3 μm thick and elastic) : made of cellulose ( 1-4 glycosidic linkage of b-D glucose) Secondary cell wall (5-10 μm thick and rigid) : 40-45% cellulose, 15-35% hemicellulose, 15-30% lignin
- 14. Function of cell wall •It protects the inner contents of the cell. •It gives definite shape to the cell. •It provides mechanical support to the tissues and act as a skeletal framework of plants. •It helps in transport of substances between two cells. • The cell wall is hydrophilic in nature and it imbibes water and helps in the movement of water and solutes towards protoplasm. • It also acts as a permeable structure during absorption of minerals and solutes.
- 15. Protoplasm •It is the living, colloidal and semi fluid substance. It is also called as cytoplasm. •Cell devoid of cell wall is called protoplast. •Protoplast is enclosed by a membrane called as cell membrane or plasma membrane.
- 16. Cell membrane • All cells are enclosed by a thin, membrane called plasma membrane or plasmalemma. • The plasma membrane and sub cellular membrane are collectivelycalled biological membrane. • Cell membrane consists of proteins, lipids and other substances. • 1. Proteins:- Intrinsic proteins or integral proteins: - Which are embedded or buried in the lipid layer.These proteins associatewith hydrophobic interactionsto the tails or fatty acid chains of the lipid layer. In addition to the hydrophobic associations,integral proteins also posses hydrophilic aminoacidresidues which are exposed at the surface of the membrane. These proteins cannot be removed easily.
- 17. Extrinsic proteins or peripheral proteins: - They are attached to the membrane surface by weak ionic interactions. These proteins are not much involvedin the architecture of membrane. Peripheral proteins are bound to hydrophilic proteins of the integral proteins protruding from the lipid layer. 2. Lipids: - The cell membrane consists of phospholipidsand glycolipids.The fatty acid chains in phospholipidsand glycolipids usually contain 16-20 even numbered carbon atoms. Fatty acids may be saturated or unsaturated. 3. Other substances like polysaccharide, salicylic acid etc. are found attached to the proteins or lipids on the membrane.
- 18. Functions of cell membrane: • The cell membrane surrounds the protoplasm of the cell, thus separating the intracellular componentsfrom the extracellular environment. • It anchors the cytoskeletonto provide shape to the cell, and in attachment to the extracellular matrix. • The plasma membrane is differentially permeable and able to regulate the transport across the membrane. • The cell membranes maintain the cell potential.
- 21. Nucleus • It is oval or spherical in shape and is generally larger in active cells than in resting cells. • A nucleus consists of three main parts viz. nuclear envelope, nucleolus and chromatin. • The nucleus is separated from the cytoplasm by a double membrane called the nuclear envelope. • The space between the outer and inner membrane is known as nuclear pores which provide direct connection between nucleus and cytoplasm. • Nucleolus is a spherical, colloidal body found in the nucleus and is the place where almost all DNA replication and RNA synthesis occur. • Chromatin is the basic unit of chromosome and contains genes which play important role in the inheritance of characters to offspring from parents.
- 23. FUNCTIONS OF NUCLEUS 1.Controls cellular functions 2.Synthesis of structural and enzymatic proteins 3.Synthesis of RNA 4.Cell division 5.Controls cell growth 6.Variation
- 24. Plastids •Plastids are double-membrane organelles which are found in the cells of plants and algae. •Plastids are responsible for manufacturing and storing of food. •These often contain pigments that are used in photosynthesis and different types of pigments that can change the colour of the cell.
- 26. •Chloroplasts are biconvex shaped, semi-porous, double membraned, cell organelle found within the mesophyll of the plant cell. They are the sites for synthesizing food by the process of photosynthesis. •Chromoplasts is the name given to an area for all the pigments to be kept and synthesized in the plant. These can be usually found in flowering plants, ageing leaves and fruits. Chloroplasts convert into chromoplasts. Chromoplasts have carotenoid pigments that allow different colours that you see in leaves and fruits. The main reason for its different colour is for attracting pollinators.
- 27. •These are basically chloroplasts that go with the ageing process. Geronoplasts refer to the chloroplasts of the leaves that help to convert into different other organelles when the leaf is no longer using photosynthesis usually in an autumn month. •Leucoplasts are the non-pigmented organelles which are colourless. Leucoplasts are usually found in most of the non-photosynthetic parts of the plant like roots. They act as a storage sheds for starches, lipids, and proteins depending on the need of the plants. They are mostly used for converting amino acids and fatty acids.
- 28. •Leucoplasts are of three types: Amyloplasts – Amyloplasts are greatest among all three and they store and synthesize starch. Proteinoplasts – Proteinoplasts help in storing the proteins that a plant needs and can be typically found in seeds. Elaioplasts -Elaioplast helps in storing fats and oils that are needed by the plant.
- 29. CHLOROPLAST
- 30. Functions of chloroplast: • The important processes of photosynthesis i.e, light and dark reactions occur within the chloroplast. • The granum is the site of NADP reduction forming NADPH+H+ and photophosphorylationi.e., formation of ATP in presence of light. Thus, light reaction of photosynthesistakes place in the granum region. • The stroma is the main site for the dark reaction of photosynthesis. • The chloroplast has its own genetic system and is self replicating. Thus, associated with cytoplasmic inheritance.
- 31. Mitochondria • Mitochondria are rod shaped cytoplasmic organelles, which are main sites of cellular respiration. Hence, they are referred to as power house of the cell. • Each mitochondrion is enclosed by two concentric unit membranes comprising of an outer membrane and an inner membrane. • The space between the two membranes is called perimitochondrial space. • The inner membrane has a series of infoldings known as cristae. The inner space enclosed by cristae is filled by a relatively dense material known as matrix. • The matrix is generally homogeneous but may rarely show finely filamentous or fibrous structures. • The matrix contains several copies of round or circular DNA molecules and 70 S ribosomes (that’s why it is also called as semiautonomous organelle)
- 32. MITOCHON DRIA
- 33. Functions • ATP, the readily available form of energy is produced in mitochondria. • Krebs cycle takes place in the matrix of mitochondria. • The enzymes of electron transport chain are found in the inner membrane or cristae of mitochondria. • Heme synthesis occurs in mitochondria. • Controls the cytoplasmic Ca2+ concentration
- 34. Ribosomes • Chemically, ribosomes are ribonucloprotein complexes. • This is a membrane less organelle • Ribosomes are of two types. Ribosomes of prokaryotes have sedimentation coefficient of 70 S and consist of two sub units of unequal sizes 50S and 30 S subunits. Ribosomes of eukaryotes have 80 S sedimentation coefficient (40S & 60 S). The two or more ribosomes become connected by a single m RNA and then may be called polyribosome. The major function of the smaller subunit of ribosome is to provide proper site for binding of mRNA and its translation. The larger subunit of ribosome supports translation and translocation processes coupled with polypeptide synthesis.
- 35. Functions • They provide the platform for protein synthesis • They have the machinery for protein synthesis.
- 37. Golgi apparatus • Golgi bodies is an assemblage of flat lying cisternae one above the other in close parallel array. • Each golgi complex has 3 to 12 interconnected cisternae which are composed of lipoproteins.
- 39. Functions • It helps in Packaging of proteins for exporting them. • It plays a role in sorting of proteins for incorporation into organelles. • It is involved in the formation of the cell wall of plant cells.
- 40. Endoplasmic reticulum • Endoplasmic reticulum arises from the outer membrane of the nucleus forming an intermediate meshed network. • It is of two types. The granular or rough endoplasmic reticulum in which the outer surface of endoplasmic reticulum is studded with ribosome and agranular or smooth endoplasmic reticulum in which the ribosomes are not attached
- 42. Functions • Rough endoplasmic reticulum is associated with the synthesis of proteins. • Smooth endoplasmic reticulum is associated with synthesis of lipids and glycogen. • It acts as an inter-cellular transport system for various substances. • It contains many enzymes which perform various synthetic and metabolic activities.
- 43. Vacuole • It is a membrane bound organelle found in plant cell and occupies most of the area in the plant cell. • A vacuole is surrounded by a single layer membrane called tonoplast. • It is an enclosed compartment filled with water containing inorganic and organic molecules including enzymes in solution. • It maintains the cell's turgor, controls movement of molecules between the cytosol and sap, stores useful material and digests waste proteins and organelles.
- 44. Functions • Isolating materials that might be harmful or a threat to the cell. • Stores waste products. • Maintains internal hydrostaticpressure or turgor within the cell. • Maintains an acidic internal pH. • Exports unwanted substancesfrom the cell. • Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole. • Most plants stores chemicals in the vacuole that react with chemicals in the cytosol. • In seeds, stored proteins needed for germination are kept in protein bodies which are modified vacuole.
- 45. Microbodies • Microbodies are ubiquitousorganelles found in the majority of eukaryotic plant cells. • They are mostly spherical and have a diameter ranging from 0.2um to 1.5um. • Two types of microbodies, peroxisomes and glyoxysomes, have been characterized. • These organelles differ in their distribution and enzyme composition, although both have the capacity to transform non-carbohydrate material into carbohydrate. • Prototoa have glycosomes and fungi have woronin bodies
- 46. Peroxisomes : • Peroxisomes are found in leaves of higher plants. • It is a small organelle present in the cytoplasm of many cells, which contains the reducing enzyme catalase and usually some oxidases. • Functions of Peroxisomes: • Peroxisomes act in parallel with chloroplast in higher plants and are believed to undertake photorespiration.
- 47. Glyoxysomes • A glyoxysome is a specialized form of peroxisome (a type of microbody) found in some plant cells, notably the cells of germinating seeds. • Glyoxysomes are temporary as they occur during transient periods in the life cycle of a plant such as in certain beans and nuts which store fats in their seeds as energy reserves. • Glyoxysomes appear in the first few days after seed germination in endosperm cells and associate closely with lipid bodies. • They disappear after the storage fats are broken down and converted into carbohydrate. • Functions of Glyoxysomes: Glyoxysomes are involved in the formation of sugars by the breakdown of fatty acids in germinating seeds.
- 48. Cytoskeleton • The cytoskeleton is scaffolding contained within the cytoplasm and is made up of protein. • The cytoskeleton is present in all cells. The cytoskeleton provides the cell with structure and shape. • There are three main kinds of cytoskeleton filaments: Microfilament: - They are composed of actin subunits. Intermediary filaments: - They function in the maintenance of cell shape by bearing tension. They also participate in the cell-cell and cell matrix junctions. Microtubules: - They are like hollow cylinders mostly comprising of 13 protofilaments which in turn are alpha and beta tubulin. They are commonly organized by the centrosome. Functions of cytoskeleton: 1. Provides mechanical support 2. Anchors organelles 3. Helps to move substances intracellular.