Plant Physiology Lecture Notes PDF

The Tasks Of Plant Physiology Dr. Reem Badr To describe and explain plant processes. To describe and explain the function of each kind of organ, tissue, cell, and cellular organelle in plants and also the function of each chemical constituent. To describe and explain how proce...

The Tasks Of Plant Physiology Dr. Reem Badr To describe and explain plant processes. To describe and explain the function of each kind of organ, tissue, cell, and cellular organelle in plants and also the function of each chemical constituent. To describe and explain how processes and functions respond to changes in the environment. ABMB B101 1 Plant Cell The Protoplasm The Protoplasm  Protoplasm Definition Protoplasm is defined as the living substance of the cell (nucleus and cytoplasm) Colorless, jellylike, in which food elements like proteins, fats, carbohydrates, mineral salt, and water  The Protoplasm The protoplasm is a colloidal complex exhibiting several properties attributed to a colloidal system. Much of the colloidal attributes of the protoplasm are due to their proteins, carbohydrates and fats, which are large, complex molecules approaching colloidal dimension. The colloidal system is an essential feature of living matter.  Solutions Solid Liquid  Solutions Solutions are groups of molecules that are mixed and evenly distributed in a system. Scientists say that solutions are homogenous mixtures. Everything in a solution is evenly spread out and thoroughly mixed. Heterogeneous mixtures have a little more of one thing (higher concentration) in one part of the system when compared to another.  Types of Solution Colloidal True Suspension Hydrophobic Electrolyte Hydrophilic Non-Electrolyte Types of Solution  1-True Solutions Is a homogeneous mixture of at least two components (solute) dissolved in solvent has the particle size of less than 1 nm(10 A). The solute does not settle down and remains evenly dispersed(Stable) Ex. Salt or sucrose in water  1-True Solutions (sugar) + (water) = Solution 12  1- True Solutions Electrolyte Non-electrolyte CRYSTALLOID IS PRODUCED Ex. Sucrose Ex. Salt is an ionic substance is a non-ionic substance Water is the most solvent in the plant cell Water is significant to plant life in several ways It is a major constituent of protoplasm. It carries mineral nutrients from cell to cell. It is a medium of metabolic reactions. Its hydrogen atom is incorporated in organic matter during photosynthesis, causes plant growth and in the metabolic end product of respiration. Water also causes cell and tissue turgidity during growth and participates in the cell elongation phase.  2-Suspension The particles are greater than 100 nm(1000 A) in size. Is a heterogeneous mixture The particles do not separate into molecules but are aggregates of molecules which can be seen with naked eye. It is an unstable system. The particles gradually settle down at the bottom of the container separated by a liquid layer Ex. powdered chalk in water 2-Suspension 3-Colloids  3. Colloidal Solutions The size of particles ranges from 1-100 nm (10-1000A)in diameter. Is a heterogeneous mixture They remain dispersed throughout water in a stable manner, forming a two-phase system: A- Liquid phase (dispersion phase) B- solid phase (dispersed phase) The colloidal particles are in the form of clusters of molecules. It is a stable system. They can be seen under the electron microscope.  3. Colloidal Solutions They easily pass-through filter paper, But colloidal particles cannot be pass through semipermeable membrane (S.P.M). Ex: Starch in water Colloid particles remain dispersed throughout water forming a two-phase system dispersion medium dispersed phase  e.g. Egg albumin, starch, gelatin Colloid particles remain dispersed throughout water forming a two-phase system  Electrical Properties Of Colloidal Particles Colloidal particles carry electric charges which may be positive or negative. For any one colloidal system the charge is the same on all the particles. The charges are due to the adsorption of free ions in the dispersion medium. The preferential adsorption of positive ions by a colloidal particle will give it a positive charge and the reverse is true of negatively charged colloidal particles. The fact that units of like charge repel each other, prevent their aggregation and precipitation.  Types Of Colloids 1. Lyophilic colloids or Hydrophilic colloids: Lyophilic colloids are liquid loving colloids (Lyo means solvent and philic means loving). If water is the dispersion medium, they are formed from a dispersed Particle surrounded by 2 stability factors: (a) A shell of electric charges. (b)A film (shell) of water around the particle.  The Properties Of Hydrophilic Colloids: They are colloids loving the dispersion medium. The colloids of living cells are of this type. They have a lower surface tension and much higher viscosity than the solvent. They are stable and not easily precipitated. It can be precipitated by dehydration to remove the water film followed by neutralization. Colloidal particle A shell of electric charge Water film  2. Lyophobic Colloids Or Hydrophobic Colloids: Lyophobic colloids are liquid hating colloids (Lyo means solvent and phobic means hating). They are formed from a dispersed particle surrounded by a shell of electric charges ONLY. There is no shell of water or dispersion medium because there is little attraction between the particles and its dispersion medium. The Properties Of Hydrophobic Colloids They are colloids hating the dispersion medium. The surface tension and viscosity are nearly the same as those of the solvent. They are less stable than hydrophilic colloids and easily precipitated by neutral salts.  Colloid Stabilizers These are substances added to a colloid to increase its stability & prevent its precipitation. Ex. gums, proteins. It forms a protective layer around the particles