1. Tardigrade
  2. Question
  3. Biology
  4. Consider the following: i. For a solution at atmospheric pressure Ψw = Ψs ii. Ψw (water potential) of a cell is affected by solute potential only iii. Ψp (pressure potential) is usually positive in xylem during the day Which of the statements given above is/are correct?

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Q. Consider the following:
i. For a solution at atmospheric pressure $\Psi_{w}$ = $\Psi_{s}$
ii. $\Psi_{w} \, $ (water potential) of a cell is affected by solute potential only
iii. $\Psi_{p} \, $ (pressure potential) is usually positive in xylem during the day
Which of the statements given above is/are correct?

NTA AbhyasNTA Abhyas 2020Transport in Plants

Solution:

Water potential of a solution is the sum total of four components: gravitational potential, osmotic(solute) potential, matric potential and pressure potential. But, since matric potential and gravitational potential are negligible, water potential is generally more affected by solute and pressure potential. Pressure potential of water during the standard stage is 0 MPa. The positive value of water potential within the cell is referred to as turgor pressure. During the day when transpiration is high, pressure potential of the xylem mostly is negative since water is evaporated and its turgor pressure is less.