1. Physiology introduction.pdf
- 1. DR. SUPRABUDDHA KUNDU ASSISTANT PROFESSOR SCHOOL OF AGRICULTURE, SVU Introduction to crop physiology
- 2. Introduction Plant physiology is a study of Vital phenomena in plant. Crop physiology is the study of the plant processes responsible for the growth, development, and production of economic yield by crop plants. Julius Sachs is considered the 'father of plant physiology'
- 3. Processes that occur in living plants are ♦ Photosynthesis ♦ Respiration ♦ Ion absorption ♦ Translocation ♦ Transpiration ♦ Stomatal opening and closing ♦ Assimilation ♦ Flowering ♦ Seed formation ♦ Seed germination
- 4. A brief history of Crop Physiology: W.L. Balls (1915): Crop physiology, with the aim of understanding the dynamics of yield development in crops, really began with the work of W.L. Balls. 1947: The concept of LAI (Leaf area index) was developed by D.J. Watson. This index has provided a more meaningful way of analyzing growth in crops, and stimulated renewed interest in crop physiology. 1950’s: Studies on photosynthetic rate of the leaf and the loss of photosynthates by respiration was studied by the development of ‘Infra Red Gas Analysis (IRGA)’method. This method has facilitated the estimation of short term rates of Photosynthesis and respiration by crops in the field.
- 5. 1953: Monsi and Saeki explained about the manner of light interception by the crop canopy with their concept of light interception coefficient. 1963: Hesketh and Moss showed that photosynthesis by leaves of Maize, Sugarcane and related tropical grasses could reach much higher rates, with less marked light saturation, than leaves of other plants. (This was the starting point for research to find other photosynthetic CO2 fixation path ways like C4, and CAM Mechanisms).
- 6. Importance of crop physiology in agriculture: Seed Physiology Seed is the most important input in agriculture. Germination of seed and proper establishment of seedling depends upon various internal and external factors. Knowledge of Seed physiology helps in understanding of different physiological and morphological changes that occur during germination. By understanding the causes and effects of dormancy, Crop physiologists have come up with different methods of breaking the seed dormancy. Optimum seedling growth and plant population By knowing the process of radicle and plumule emergence and their function we can achieve best plant health, which is the outcome of best plant physiology.
- 7. Growth measurement of crops The first prerequisite for higher yields in crops is high total dry matter production per unit area. High dry matter production is a function of optimum leaf area (Optimum leaf area Index) and Net Assimilation rate. (CGR = LAI X NAR). Mode of action of different weedicides The use of herbicides to kill unwanted plants is widespread in modern agriculture. Majority of Herbicides -about half of the commercially important compounds— act by interrupting photosynthetic electron flow (Ex. Paraquat, diuron) or electron flow of respiration. Nutriophysiology Nutriophysiology is yet another important area to under stand crop physiology. For the healthy growth of a crop around 17 essential elements are required. Knowledge of nutriophysiology has helped in identification of essential nutrients, ion uptake mechanisms, their deficiency symptoms and corrective measures.
- 8. Photoperiodism Response of plant to the relative length of day and night is called as photoperiodism. This concept was used to choose photo insensitive varieties. The semi dwarf Rice varieties that have revolutionized Indian agriculture, are lodging resistant, fertilizer responsive, high yielding and photo insensitive. Plant growth regulators Plants can regulate their growth through internal growth mechanisms involving the action of extremely low concentrations of chemical substances called Plant growth substances, phytohormones or Plant growth regulators. The regulation of flowering, seed formation and fruit setting has been controlled through the application of different hormones at the appropriate time of plant height and age.
- 9. Plant cell: an Overview The cell (Latin word, meaning "small room") is the basic structural, functional, and biological unit of all known living organisms The cell was discovered by Robert Hooke in 1665
- 11. Cell theory Cell theory, first developed in 1839 by Matthias Jakob Schleiden and Theodor Schwann, states that 1) All organisms are made up of one or more cells and the products of those cells. 2) All cells carry out life activities (require energy, grow, have a limited size). 3) New cells arise only from other living cells by the process of cell division.
- 12. Description of the plant cell 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 1. Middle Lamella 2. Primary cell wall (1-3 µm thick and elastic) 3. Secondary cell wall (5-10 µm thick and rigid)
- 13. Protoplasm : It is the living, colloidal and semi fluid substance. Cell devoid of cell wall is called protoplast. Protoplast is enclosed by a membrane called as cell membrane or plasma membrane. Cell membrane : All cells are enclosed by a thin, membrane called plasma membrane or plasmalemma. The plasma membrane and sub cellular membrane are collectively called biological membrane. Cell membrane consists of proteins, lipids and other substances.
- 14. Cell nucleus : It is oval or spherical in shape and is generally larger in active cells than in resting cells. A nucleus consists of Four main parts viz. nuclear envelope, nucleoplasm, 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.
- 15. Chloroplast : Chloroplasts are organelles found in plant cells and other eukaryotic organisms that perform photosynthesis because of the presence of green pigment, chlorphyll. The chloroplast is surrounded by double layered membrane. The space between these two layers is called intermembrane space. Stroma is the aqueous fluid found inside the chloroplast. The stroma contains the machinery required for carbon fixation, circular DNA, 70 S ribosomes (that’s why called as semiautonomous organelle) etc. within the stroma the stacks of thylakoids are arranged as stacks called grana.
- 16. 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.
- 17. Ribosomes : Chemically, ribosomes are ribonucloprotein complexes. This is a membrane less 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). 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.
- 19. Golgi apparatus: A Golgi apparatus is composed of flat sacs known as cisternae. The sacs are stacked in a bent, semicircular shape. Each stacked grouping has a membrane that separates its insides from the cell's cytoplasm. A Golgi body, also known as a Golgi apparatus, is a cell organelle that helps process and package proteins and lipid molecules, especially proteins destined to be exported from the cell.
- 20. 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. 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. 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.
- 21. 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: 1. Microfilament: - They are composed of actin subunits. 2. Intermediary filaments: - They function in the maintenance of cell shape by bearing tension. They also participate in the cell-cell and cell matrix junctions. 3. 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.
- 22. Thank You