Measuring Osmotic Pressure of Sap within Live Cells by Means of a Visual Melting Point Apparatus | Zendy

Bradford C. Bearce | Zendy; Harry C. Kohl | Zendy

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Measuring Osmotic Pressure of Sap within Live Cells by Means of a Visual Melting Point Apparatus

Author(s) -

Bradford C. Bearce,

Harry C. Kohl

Publication year - 1970

Publication title -

plant physiology

Language(s) - English

Resource type - Journals

SCImago Journal Rank - 3.554

H-Index - 312

eISSN - 1532-2548

pISSN - 0032-0889

DOI - 10.1104/pp.46.4.515

Subject(s) - osmotic pressure , melting point , biophysics , chemistry , point (geometry) , biology , biochemistry , mathematics , geometry , organic chemistry

A freezing slide apparatus is described for visual observation of freezing water and melting ice within plant cells. The slide consists of an ordinary microscope slide glued into a Plexiglass jacket, through which cold 90% ethyl alcohol is pumped at varying rates for temperature control. Temperature is recorded by means of an iron-constantan thermocouple wire (25-micron diameter) connected to a recording potentiometer. Tissue strips were quick frozen (at a cooling rate of 33 C per (1/2) minute) and then warmed very slowly (at a rate of 2 C per minute) for observation of melting points. This apparatus has been used to determine osmotic pressures of cell sap of guard and adjoining epidermal cells of Chrysanthemum morifolium and Pelargonium hortorum. An accuracy of +/- 1.2 atmospheres is possible. Wide variations among osmotic pressures of both guard and epidermal cells were found at any one stomatal aperture in both species.

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