Final answer:
The concentration of the cytoplasm in potato cells at the start of the experiment can be determined by comparing it with the external solution's concentration and observing the cells' osmotic behavior.
Step-by-step explanation:
The concentration of the cytoplasm in the potato cells at the start of the experiment can be inferred based on the osmolarity of the external solution the cells are placed in. If the cells are placed in a hypertonic solution, such as one where the external NaCl concentration is 1.4 M, the cells would lose water and shrink. Conversely, if placed in a hypotonic solution, they would gain water and swell. To maintain osmotic balance, cells adjust their internal solute concentrations, such as synthesizing glycerol, to match the external environment. Thus, the initial cytoplasm concentration of potato cells can be estimated by comparing it with the known concentration of the external solution and observing the cells' behavior.