If too much water has been lost or not enough water is available, a plant will begin to wilt. When this happens the cells of a plant become flaccid.
Occasionally an embarrassing situation.
pressure potential would be zero
If a plant cell is flaccid, water has escaped from inside the cell to the outside, by osmosis. Under a microscope, the cell membrane can be seen to detach itself from the cell wall.
Plant cells are covered by cell wall.