Pressure potential of a flaccid cell is 0 MPa

Explanation:
The pressure potential of a flaccid cell is zero. This means that there is no pressure exerted on the cell wall by the cell contents. The pressure potential is a component of the water potential, which determines the movement of water in and out of the cell.

Water Potential:
Water potential is a measure of the potential energy of water in a system. It is influenced by two main factors: solute potential and pressure potential. Solute potential is the potential energy of water due to the presence of solute molecules, while pressure potential is the potential energy of water due to the pressure exerted on it.

Pressure Potential:
Pressure potential is the component of water potential that is due to the pressure exerted on water. It can be positive or negative depending on whether the pressure is greater or less than atmospheric pressure. When a cell is flaccid, there is no pressure exerted on the cell wall, and therefore the pressure potential is zero.

Flaccidity of a Cell:
Flaccidity refers to the state of a plant cell when it lacks turgor pressure. Turgor pressure is the pressure exerted by the cell contents against the cell wall, and it is required for the cell to maintain its shape and rigidity. When a cell is flaccid, it becomes limp and loses its shape.

Reason for Zero Pressure Potential:
The pressure potential of a flaccid cell is zero because there is no turgor pressure exerted on the cell wall. This can occur when there is a loss of water from the cell, such as in a dehydrated or wilted plant. In these cases, the cell loses water and the pressure inside the cell decreases, resulting in a flaccid state.

Importance of Pressure Potential:
Pressure potential plays a crucial role in plant physiology. It helps in maintaining the shape and rigidity of plant cells, which is important for their functioning. Turgor pressure provides mechanical support to the plant, allowing it to stand upright. It also facilitates the movement of water and nutrients within the plant.

Conclusion:
The pressure potential of a flaccid cell is zero because there is no turgor pressure exerted on the cell wall. This can occur when there is a loss of water from the cell, resulting in a loss of rigidity and shape. Pressure potential is an important component of water potential and plays a crucial role in plant physiology.