Final answer:
The cells of Elodea swell in distilled water due to its hypotonic nature, and the cell wall prevents the cells from bursting by providing structural support and limiting expansion.
Step-by-step explanation:
The aquatic plant Elodea was placed in distilled water and a 10% sodium chloride solution. The cells of Elodea would have swelled in the distilled water, as it is a hypotonic solution compared to the interior of the plant cells. In contrast, the 10% sodium chloride solution is hypertonic, causing the cells to lose water and shrink. The mechanism that prevents plant cells from bursting in a hypotonic environment, such as distilled water, is primarily due to the cell wall that surrounds the plasma membrane. The cell wall provides structural support and limits the extent to which the plasma membrane can expand, thus preventing lysis (bursting) of the plant cells. Additionally, the turgor pressure produced by the inflow of water into plant cells helps to maintain the structural integrity of nonwoody plants.