Protoplasts. Coloured scanning electron micrograph (SEM) of two tobacco plant (Nicotiana tabacum) protoplasts fusing. A protoplast is a plant cell that has had its tough outer cell wall removed by chemical treatment. This leaves an intact cell with its contents surrounded by its plasma membrane. The cell wall can later be regrown. Fusing protoplasts from two different species into a single cell can produce a hybrid plant. Protoplasts are used instead of intact cells in plant genetic engineering as they are easier to manipulate. Magnification: x2500 when printed 10 centimetres wide.