What characteristic defines a cell membrane disruptor?

A cell membrane disruptor is defined by its ability to kill plants by targeting and damaging their cell membranes. The cell membrane is crucial for maintaining the integrity of the plant cell as it regulates the flow of substances in and out of the cell. When a substance disrupts this membrane, it can lead to cell leakage, loss of turgor pressure, and ultimately cell death. This mechanism can be especially effective against unwanted aquatic vegetation, making cell membrane disruptors a key tool in pest control.

The other options, while related to plant physiology, do not accurately describe the function of a cell membrane disruptor. Promoting plant growth, enhancing nutrient absorption, or increasing water retention address beneficial processes that support plant health, but they do not involve the destructive impact on cell membranes that characterizes cell membrane disruptors. Therefore, the unique action of damaging the cell membrane is what solidifies option C as the correct identification of a cell membrane disruptor.