Introductory Crop Physiology

PRESSURE POTENTIAL

The hydrostatic pressure exerted by the protoplasm against the cell wall as a result of entry of water is called as turgor pressure. The potential created by such pressures is called pressure potential.
The pressure potential is usually positive and operates in plants as wall pressure and turgor pressure

• In a partially turgid cell, ?w: ?s + ?p (High water potential).
• In a fully turgid cell, ?w: Zero (Highest water potential).
• In a flaccid or plasmolysed cell, ?w = ?s (Lowest water potential).

Water potential in a system can be decreased by;

• Addition of water soluble solutes.
• Negative pressure /tension [in plant system i.e., xylem]
• Reduction in temperature

Water potential in a system can be increased by;

• Positive pressure.
• Increase in temperature.

Water potential is experimentally determined by the following methods.

• Tissue-volume method
• Gravimetric method
• Vapour pressure or thermo couple method
• Pressure bomb method
• Chardakov’s method

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