Prokaryotic cells osmotic pressure

The peptidoglycan (protein and oligosaccharide) cell wall protects the prokaryotic cell from mechanical and osmotic pressure. A Gram-positive bacterium has a thick cell wall surrounding the plasma membrane, whereas Gram-negative bacteria have a thinner cell wall and an outer membrane, between which is the periplasmic space. 

Plant and prokaryotic cells are surrounded by a rigid cell wall that protects them against osmotic stress, but eukaryotic cells exist in vivo in tissues where the extracellular medium has very similar osmolarity to that inside the cells thus there is normally no net osmotic pressure difference across the plasma membrane. 

---