Water
This flowering plant does not wilt but stands straight up, reaching toward the sunlight, because its cells contain mostly water.
Water is ultimately important to the life of plants as it allows plants to perform its everyday processes by supplying plant’s essential nutrients. When a plant cell is filled with water, it pushes firmly against the cell walls. This effect is known as turgor pressure and it makes the structure of plants (stem tissues and leaves) to become rigid, allowing it to stand upright and prevent it from wilting.