The cell sap vacuole in plants is much larger than animals. In plant cells the vacuoles are usually very large and are permament and have the same function. In addition to storing important substances, it also helps support the plant. The pressure of water filling the cell vacuole pushes out against the cell wall. This gives the wall enough strength to hold up fairly large green plants. We all know the first indication that we are not giving our house plants enough water. They start to droop or wilt. Now you know why, so keep that cell sap vacuole filled with water.