Turgor

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Osmotic states of a plant cell (plasmolysis)

In plant physiology and cell biology, the pressure of the cell sap on the cell wall is referred to as turgor (also turgor pressure ) .

If the osmotic value in the cell is higher than in the surrounding apoplast , it absorbs water through deplasmolysis. The increasing pressure inside tensions the surrounding cell wall. The turgor is absorbed by the elastic wall pressure that counteracts it. If the turgor has its greatest possible value, one speaks of full turgescence or a fully turgescent cell . If, on the other hand, the osmotic value of the surrounding environment is greater than that in the cell sap ( hypertonic environment), the turgor decreases and the protoplast detaches from the cell wall (→ plasmolysis). The strength of herbaceous , non- woody plants is based on the interplay of turgor and wall pressure .

Turgor and water potential

The osmotic value contributes to the water potential via the negative osmotic pressure (as "osmotic potential") . The difference in water potential between the cell and its environment determines whether the cell absorbs or releases water. Water moves towards the more negative potential; pure water has the highest possible value, namely 0. Dissolved and colloidal substances increase the osmotic value of the cell sap and reduce the water potential of the cell. If this is lower than the water potential of the surrounding environment, water flows through the plasma membrane and tonoplast into the protoplast, thus increasing the turgor. At full turgescence, the water potential of the cell or tissue reaches the value 0, at which water can no longer be absorbed. However, this state is seldom reached because the perspiration suction in the plant reduces the water potential in the apoplast.

The turgor in plant cells is 0.07 to 4  megapascals .

Effects of the turgor

Basil (Ocimum basilicum) on restoring the turgor after watering

Glandular tissue can secrete secretions with the help of the turgor . By changing the turgor of the sphincter or secondary cells , the plant can control the state of the opening of the stomata ( stomata ). The leaf movements ( nastia ) of the mimosa caused by vibrations are also based on local changes in the turgor. Some plants ( juice pressure spreader) spread their seeds with the help of turgor slingshots ( spring herbs ) or turgor spray mechanisms. Pressures of up to 1.5 megapascals (approx. 150 bar) and ranges of up to 12 meters ( spray cucumber ) can be achieved.

literature

Web links

Wiktionary: Turgor  - explanations of meanings, word origins, synonyms, translations

Individual evidence

  1. ↑ Hans Kleinig, Uwe Maier: Cell Biology. A textbook . Founded by Hans Kleinig and Peter Sitte. 4th edition. Fischer, Stuttgart 1999, ISBN 3-437-26010-3 .