The form and structure of growing cell is maintained due to

The form and structure of the growing cell are maintained due to Turgidity.
Turgidity is the point at which the cell's membrane pushes against the cell wall, which is when turgor pressure is high.
The fact of being swollen or firm is usually because of being full of liquid. Water is essential to maintain the turgidity of cells, and ultimately to retain the proper form and structure of any cell.