In an experiment with four plants grown under different light conditions, what serves as the control?

• A. All plants receiving 50% light
• B. Plants growing in 100% light
• C. The two plants in 50% light
• D. The amount of water provided

Answer: (B)

In an experimental setup, a control serves as a standard for comparison against the experimental groups. In this context, plants grown in 100% light would be considered the control because they are exposed to the maximum amount of light, allowing researchers to observe how the other light conditions (such as 50% light) affect plant growth relative to optimal light availability.

When assessing the impact of varying light levels on plant growth, the plant group receiving full light (100%) represents an unaltered baseline for growth potential. This is crucial for determining whether reduced light conditions (like 50% light) positively or negatively affect the plants compared to ideal growth conditions, thus providing valuable insight into the light requirements for healthy plant growth.

The other options do not fit the role of a control. The plants in 50% light either represent conditions to be tested or variations within the experiment rather than a baseline. The amount of water, while important for growth, does not serve as a comparative standard for light conditions specifically.