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Savitribai Phule Pune University, Pune, E-content Develope, for, , F. Y. B. Sc. Botany, BO-122: PRINCIPLES OF PLANT SCIENCE, SEMESTER-II: PAPER-II - Credit-1, , PLANT PHYSIOLOGY AND CELL BIOLOGY, , INTRODUCTION TO PHYSIOLOGY, AND DIFFUSION, Dr. Sonawane H.B., Department of Botany, Prof. Ramkrishna More Arts Commerce and, Science College, Akurdi, Pune, [email protected]

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Plant Physiology, • Plant physiology is as the physiological processes or functions of plants., • Plant physiology is the study of the vital processes occurring in plants, deals with the functions and processes occurring in plants, • It is a descriptive study of structure and variation of plants at the, cellular and molecular level leading to ecological, physiological and, biochemistry related aspects of plants exploration., • Plant physiology gives an account of the different parts of the plant and, their functioning., • Plant physiology helps us analyze plant processes such as mineral, nutrition, photosynthesis, transpiration, ascent of sap, respiration and, finally plant development and growth which are characteristics, exhibited by living entities., • It also gives a brief idea of the role of physiological processes in the, environment.

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• The natural activity of the cells, tissues, organs and organisms is referred, to as their function., • A plant physiologist must understand, describe and explain these, functions as well., • These functions are explained at the cellular and molecular levels. In plant, physiology, an attempt is also made to study the factors which modify, growth and development.

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SCOPE OF PLANT PHYSIOLOGY, • Plant physiology has various subdisciplines, amongst, them, phytochemistry,, Biochemistry and phytopathology are, important., • The scope of plant physiology as a, discipline may be divided into several, major areas of research., • Phytochemistry is included within the, domain of plant physiology. To function, and survive, plants produce a wide array of, chemical compounds not found in other, organisms. Photosynthesis a important, physiological process requires a large, number of pigments, enzymes and other, compounds to function.

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• plant physiology includes the study of biological and chemical processes of, individual plant cells., • Cell Biology: Plant cells also contain chlorophyll, a chemical compound that, interacts with light in a way that enables plants to manufacture their own, nutrients., • Morphology and Anatomy: plant physiology deals with interactions between, cells, tissues, and organs within a plant., • Different cells and tissues are physically and chemically specialized to perform, different functions., • The functioning of the various modes of transport is studied by plant, physiologists., • plant physiologists study the ways that plants control or regulate internal, functions., • In growth and development of the plants, produce chemicals called hormones, which are produced in one part of the plant to signal cells in another part of the, plant to respond., • Photoperiodism - Many flowering plants bloom at the appropriate time, because of light-sensitive compounds that respond to the length of the night., • Environmental physiology: Study of plant response to environmental conditions, and their variation. Various Stress can be studied in this field.

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Diffusion, • The movement of particles or molecules or ions from a region of higher, concentrations to a region of lower concentration due to kinetic energy, of the particles is called as diffusion., • The rate of diffusion of gases is faster than liquids or solutes., • The diffusing particles have a certain pressure called as the diffusion, pressure which is directly proportional to the number or concentration of, the diffusing particles (movement of molecules from high diffusion, pressure to low diffusion pressure)., , • Diffusion occur between gas and gas (e.g., diffusion of ammonia into air),, liquid and liquid (e.g., diffusion of alcohol into water), or solid and liquid, (e.g., diffusion of sugar into water)., , Source: AskIITians0

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• From soil, water and ions of simple inorganic salts pass into plants, through the root cells by a process which is basically diffusion, though, greatly modified by other factors., • The water and solutes pass through the, dead and living vessels and also from, cell to cell by diffusion., Image courtesy: Science Photo Library Ltd / Getty Images, , • When a crystal of copper sulphate is placed in a beaker containing, water, a dense blue colour is seen around the crystal., , Image courtesy: Byjus, , Source: AskIITians0

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Factors affecting rate of diffusion, • Higher temperature increased the rate of diffusion., • Lighter molecules will diffuse faster than the heavier molecules., • The rate of diffusion of gases is directly proportional to the pressure. So the, rate of diffusion increases with increase of pressure., , • Diffusion of more than one substance at the same time and place may be at, different rates and in different direction, but is independent of each other., • A very common example of this is the gaseous (CO2 and O2) exchange in plants., Besides osmotic diffusion, the above mentioned simple diffusion also plays a, very important role in the life of the plants., • The permeability of a membrane affects the rate of diffusion. Diffusion rate, increases as membrane permeability increases., Source: AskIITians0

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Significance of diffusion, • Gaseous exchange during the processes of photosynthesis and respiration, takes place with the help of diffusion., , • The process of diffusion is involved in the transpiration of water vapours., • Aroma of flowers is due to diffusion of volatile aromatic compounds to, attract pollinating animals., , • During passive salt uptake, the ions are absorbed by process of diffusion., • Diffusion helps in translocation of food materials., • Gaseous exchange in submerged hydrophytes is takes place by general, surface of the cells through diffusion., , Source: AskIITians0

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Imbibition as a special type of diffusion., • Imbibition takes place when water is absorbed by inmibed causing an increase, in volume., • The special type of diffusion in which an Solid-colloids absorbs water on its, surface without dissolving in it is called imbibition, • Examples:, • Dry plant material like dry wood is placed in water. It swells and its volume, increases., • Dry pea seeds are placed in water. These also swell. It helps in the germination, of seed., • Imbibition is also diffusion since water surface potential movement is along a, concentration gradient; the seeds and other such materials have almost no, water hence they absorb water easily. Water potential gradient between the, absorbent and the liquid imbibed is essential for imbibition.

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• Imbibition of water increases the volume of the imbibant, which results, in imbibitional pressure., • This pressure can be of tremendous magnitude., • It is demonstrated by the splitting of rocks by inserting dry wooden, , stalks in the crevices of the rocks and soaking them in water, a, technique used by early Egyptians to cleave stone blocks., • It is the first step in the germination of seeds., , • See this https://www.youtube.com/watch?v=PlobtjsRRto .

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Reference, •Plant Physiology (Biology 327) - Dr. Stephen G. Saupe; College of St. Benedict/ St. John's University., , • AskIITians., • NCERT

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Thank You…………