What gives plants structure?

actually to be more specific i believe it is the cellulose that allows the plant to keep its structure. It is the tough bundled fiber that is very strong. Similarly the vacuoles are used to keep the plant erect. the vacuoles store water within the plant and pushes against the plant walls, when the vacuoles are not full enough the plant will become flaccid thus vacuoles are responsible for the structural integrity of the plant.