Turgor pressure, cell elongation

The plasma membranes of growing plant cells select to incorporate sugars, amino adds, ions and other low molecular weight compounds from the apoplastic space, and then, the cells have a certain level of osmotic pressure. The difference between their osmotic pressure and their wall pressure (=turgor pressure) is due to motive power (suction force) to suck water from the apoplastic space (Figure 1). The plant hormone auxin, which decreases the wall pressure in a growing plant cell, therefore induces cell elongation or expansion. 

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