Introduction:
Water is very important to plant life and well being. It forms 80-90% of fresh weight of plants. Plants develop in soil and absorb water and minerals that is accessible in soil. So water has great significance for plants. Water functions as the reactant and a product. Water and dissolved substances are transported inside and outside cell through procedure of diffusion and osmosis. The understanding of plant water relations relies on understanding of principle of diffusion and osmosis.
Diffusion:
Diffusion is movement of molecules or ions of liquid, solid or gas from area of the greater concentration to the area of lesser concentration. Diffusion continues till dynamic equilibrium is established. At this phase of dynamic equilibrium, movement of molecules is equivalent in both directions thus, diffusion procedure stops because of equal movement of molecules. On account of the kinetic energy that is present in molecules, substances are distributed all through available space. Movement of molecules relies on kinetic energy during diffusion. Movement of molecules happens from the higher energy towards the lower energy. Diffusion of one substance is independent of the other.
Diffusion pressure:
As molecules diffuse from region of higher concentration to area of lower concentration, diffusing molecules likely to apply the type of pressure called as diffusion pressure. This is developed because of difference in concentration of molecules of materials. Diffusion pressure is high at larger concentration and low at smaller concentration. Diffusion pressure of the pure solvent is forever higher than its solution. Water molecules moves from the higher concentration to lower concentration in plants.
Factors affecting rate of diffusion:
Temperature:
Rate of diffusion is directly proportional to temperature, it signifies rate of diffusion increases with increase in temperature. Rate of diffusion α temperature. Diffusion stops roughly at 0°C.
Density:
Rate of diffusion is inversely proportional to square root of the relative density. It signifies rate of diffusion lowers down with increasing density. Diffusion of materials is in following sequence according to the density. Rate of diffusion is greatest in gas, followed by liquid and least in solid.
Pressure:
Rate of diffusion is directly proportional to pressure, it signifies rate of diffusion increases with increase in pressure. Rate of diffusion α pressure.
Size of molecule:
Diffused molecules/atoms/ions are inversely proportional to the size and mass. The rate of diffusion reduces with increase in size.
Importance of diffusion:
Permeability:
Permeability refers to exchange of materials through the membrane. There are four different kinds of membranes on basis of the permeability:
Permeable membranes:
These are membranes which permit movement of both - solutes and solvent through them, like cellulosic cell wall.
Impermeable membranes:
These are membranes which don't permit movement of substances through them, example cutinized cell wall.
Semi permeable membranes:
These are membranes that permit passage of solvent molecules but don't permit passage of solutes, example parchment membrane, celloidin membrane.
Selectively-permeable membrane or differentially permeable membranes:
These are membranes that permit selective solutes to pass through them along with solvent molecules, like plasma membrane, tonoplast. This membrane is permeable for N2, O2, CO2, gases and alcohol, ether and water; but impermeable for proteins and polysaccharides.
Osmosis:
Osmosis is movement of solvent or water molecules from region of the higher diffusion pressure or free energy to region of the lower diffusion pressure or free energy across the semi-permeable membrane.
When the cell is placed in hypertonic solution, water molecules emerge from cell in outer solution. This is termed Exosmosis. It is movement water molecules out of cell. Due to exosmosis, protoplasm shrinks and leaves cell wall and therefore, cell becomes flaccid, that is known as plasmolysed cell and phenomenon is called plasmolysis. Therefore, exosmosis leads to plasmolysis. Though, endosmosis is entry of water molecules in cell during osmosis. If plamolysed (flaccid) cell is placed in hypotonic solution water enters in cell. Endosmosis makes restores turgidity of cell.
Osmotic pressure:
Osmotic pressure can be stated as pressure that is developed in the solution in which solution and water is divided by semi-permeable membrane or as hydrostatic pressure developed in solution that is just sufficient to stop entry of solvent in solution when two are divided by the semi-permeable membrane. Osmotic pressure of water is zero. This is because of presence of solute in solution. Osmotic pressure of solution is directly proportional to concentration of solute in it. Osmotic pressure illustrates maximum variation in plants cells. Highest osmotic pressure is found in halophytes. Lowest osmotic pressure is found in aquatic plants or hydrophytes. Osmotic pressure of the solution is estimated by osmometer. Value of osmotic pressure relies on concentration of solution, the higher the concentration of solutes in solution, the greater the osmotic pressure. Osmotic pressure of solution is estimated mathematically as follows:
OP = mRT
where m = molar concentration
R = Gas constant [0.082 mole/molecules]
T = Absolute temperature
Factors affecting osmotic pressure
a) Concentration: Osmotic pressure of the solution increases with increase in concentration of the solutes.
b) Temperature: Osmotic pressure of the solution is proportional to temperature. This means that as temperature increases osmotic pressure also increases.
c) Dissociation of solutes also increases osmotic pressure of solution.
Importance of osmosis:
Tutorsglobe: A way to secure high grade in your curriculum (Online Tutoring)
Expand your confidence, grow study skills and improve your grades.
Since 2009, Tutorsglobe has proactively helped millions of students to get better grades in school, college or university and score well in competitive tests with live, one-on-one online tutoring.
Using an advanced developed tutoring system providing little or no wait time, the students are connected on-demand with a tutor at www.tutorsglobe.com. Students work one-on-one, in real-time with a tutor, communicating and studying using a virtual whiteboard technology. Scientific and mathematical notation, symbols, geometric figures, graphing and freehand drawing can be rendered quickly and easily in the advanced whiteboard.
Free to know our price and packages for online biology tutoring. Chat with us or submit request at [email protected]
Organic, Inorganic and Metallic Pigmentsigments tutorial all along with the key concepts of Organic pigments, Key Features of Organic Pigments, Inorganic pigments, Differences between Organic and Inorganic Pigments, Differences between Organic and Inorganic Pigments
Photochemistry and Pericyclic Reactions tutorial all along with the key concepts of Photochemical reaction, tunicate, Consequences of photo excitation, Pauli Exclusion Principle
tutorsglobe.com process of urea assignment help-homework help by online urea cycle tutors
Introduction to Quantum Chemistry tutorial all along with the key concepts of History of Quantum Mechanics, Electronic structure, Wave model, Valence bond, Molecular orbital, Density functional theory, Chemical dynamics, Adiabatic chemical dynamics
theory and lecture notes of analysis of ac networks, all along with the key concepts of combined reactances, argand diagram and kirchhoff’s laws. tutorsglobe offers homework help, assignment help and tutor’s assistance on analysis of ac networks.
www.tutorsglobe.com offers variance analysis homework help, variance analysis assignment help, answering questions to variance analysis accounting solutions, online tutoring by tutors.
tutorsglobe.com welfare assignment help-homework help by online intermediate microeconomics tutors
Modern Art Assignment Help is an effectual means to score your desired grades without putting your hands in complex tasks.
Theory and lecture notes of Cournot Duopoly all along with the key concepts of cournot duopoly, cournot duopoly Assumptions, Cournot-Nash Equilibrium, Generalization to Oligopoly. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Cournot Duopoly.
some colligative properties tutorial all along with the key concepts of vapor pressure lowering, raoult's law, boiling point elevation, freezing point depression and osmotic pressure
tutorsglobe.com vitamins assignment help-homework help by online nutrition tutors
www.tutorsglobe.com offers chemical thermodynamics homework help, chemical thermodynamics assignment help, online tutoring, chemical thermodynamics solutions and instant help in projects by online chemistry tutor's help.
www.tutorsglobe.com offers Code Reviews homework help, assignment help, case study, writing homework help, online tutoring assistance by computer science tutors.
Theory and lecture notes of Future of Macroeconomics all along with the key concepts of future of macroeconomics, Past of Macroeconomics, Age of John Maynard Keynes, Real Business Cycle Theory, Keynesian Economics. Tutorsglobe offers homework help, assignment help and tutor’s assistance on Future of Macroeconomics.
tutorsglobe.com heredity assignment help-homework help by online concept of heredity and variation tutors
1934444
Questions Asked
3689
Tutors
1465950
Questions Answered
Start Excelling in your courses, Ask an Expert and get answers for your homework and assignments!!