Practical: Study of Nostoc

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 Practical: Study of Nostoc Nostoc is a filamentous, photosynthetic cyanobacterium. It commonly occurs in freshwater, moist soil, wet rocks and other damp habitats. Colonies are usually gelatinous because numerous filaments remain embedded in a mucilaginous matrix. Materials Required Fresh or preserved Nostoc material, clean glass slide, cover slip, dropper, dissecting needle, water, blotting paper and compound microscope. Procedure Take a small quantity of Nostoc colony with the help of a dissecting needle and place it on a clean glass slide. Add one or two drops of water and gently tease the material so that the filaments become separated. Place a cover slip carefully over the material without trapping air bubbles. Remove excess water with blotting paper. First observe the preparation under low power and then under high power of the compound microscope. Observations The plant body of Nostoc is thalloid and usually forms a soft, jelly-like colony. A colony contains numerous ...
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Osmotic potential

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Osmotic potential

       Osmotic pressure of a solution may also be defined as the excess hydrostatic pressure which must be applied to it order to make it water potential equal to that of pure water. Since in a literal sense, no actual pressure is developed, unless the solution is placed in an osmometer, it is preferable to use the term osmotic potential instead of osmotic pressure. Osmotic potential being equal in magnitude but opposite in sign to osmotic pressure (π). Thus π = ᴪs (osmotic potential).

       Since the osmotic potential of dilute solution of sucrose is directly proportional to the concentration of solute and the absolute temperature. On the basis of Vant Hoff’s equation, op can therefore be written as-

       ᴪs (o.p.) = -n/v RT

       where n is the  number of mol of solute in solution of volume V, R is the gas constant and T is the absolute temperature.

       o.p depends on the total number of solute particles in solution rather than on their kinds or their charges. So, the op of an electrolytes is lower than the non electrolyte.

       o.p in plant cells also vary widely from species to species. a daily rise and fall of o.p is common occurrence during the growing season of a plant. This is due to water content in leaves.

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